Synth-DIY Yahoo! Groups Archives

Attaching two PCBs together

2017-07-18 by Brad

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

Re: [Homebrew_PCBs] Attaching two PCBs together

2017-07-18 by Harvey Altstadter

Brad,

I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".

There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.

If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.

If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150°C. Others are lower, but then it will depend on what you can find.

I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.

Good luck in your search.

Harvey A.

On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-19 by Jeff Heiss

The material used to glue layers together in multilayer boards is called prepreg. I don’t see prepreg sold online anywhere though. Not even Ebay.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 7:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,

I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".

There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.

If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.

If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150°C. Others are lower, but then it will depend on what you can find.

I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.

Good luck in your search.

Harvey A.

On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-19 by Andrew Volk

Brad –

Use a vacuum press. Vacuum is useful for many things, especially if you are also into woodworking (veneering), molding, etc. The vacuum will draw the bubbles out. Vacuum pumps are available from Harbor Freight. Just need a few fittings and a reinforced hose and a chamber or bag in which to put the boards. (See http://www.veneersupplies.com/pages/DIY__Vacuum__Press.html).

Andrew V.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 6:15 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

The material used to glue layers together in multilayer boards is called prepreg. I don’t see prepreg sold online anywhere though. Not even Ebay.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 7:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,

I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".

There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.

If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.

If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150°C. Others are lower, but then it will depend on what you can find.

I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.

Good luck in your search.

Harvey A.

On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

Re: [Homebrew_PCBs] Attaching two PCBs together

2017-07-19 by Harvey Altstadter

Jeff,

I found prepreg on the manufacturer sites, but no where to actually buy it in small quantities. It makes sense because it is used in large sheets, not suitable for home use.

Harvey A.

On 7/18/2017 6:15 PM, 'Jeff Heiss' jeff.heiss@... [Homebrew_PCBs] wrote:

The material used to glue layers together in multilayer boards is called prepreg. I don’t see prepreg sold online anywhere though. Not even Ebay.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 7:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,

I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".

There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.

If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.

If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150°C. Others are lower, but then it will depend on what you can find.

I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.

Good luck in your search.

Harvey A.

On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

Re: [Homebrew_PCBs] Attaching two PCBs together

2017-07-19 by Harvey Altstadter

Brad,

As Andrew V. mentioned, vacuum bagging is an effective process for laminating. There are a couple of issues when using epoxy, or any resin that requires mixing. Mixing the resin and hardener introduces air bubbles into the epoxy. It is true that the vacuum will pull the air out, but a better way is to degas the resin before you apply it. Lots of descriptive material on the epoxy manufacturer's sites. The fly in the ointment is that the epoxy is curing while you are doing this. You need to use an epoxy with a relatively long pot life. Once the epoxy is degassed, you can apply it to your board and process in the vacuum bag. In both vacuum operations, it is important to have some kind of "filter" in the vacuum line to keep the volatiles that the vacuum pulls out of the epoxy out of the pump.Otherwise, the pump will eventually get gunked up with this material. A water bath might work, or a large chamber that slows down the flow to where the volatiles condense on the surfaces, rather than entering the pump.

Here is a reference to the degassing process: www.epotek.com/site/files/Techtips/pdfs/tip4.pdf

Another thing you should give a thought to, is how to produce an epoxy layer with a uniform thickness.

Harvey A.

On 7/18/2017 6:57 PM, 'Andrew Volk' amvweb@... [Homebrew_PCBs] wrote:

Brad –

Use a vacuum press. Vacuum is useful for many things, especially if you are also into woodworking (veneering), molding, etc. The vacuum will draw the bubbles out. Vacuum pumps are available from Harbor Freight. Just need a few fittings and a reinforced hose and a chamber or bag in which to put the boards. (See http://www.veneersupplies.com/pages/DIY__Vacuum__Press.html).

Andrew V.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 6:15 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

The material used to glue layers together in multilayer boards is called prepreg. I don’t see prepreg sold online anywhere though. Not even Ebay.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 7:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,

I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".

There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.

If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.

If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150°C. Others are lower, but then it will depend on what you can find.

I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.

Good luck in your search.

Harvey A.

On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-19 by Andrew Volk

Harvey, Brad –

A PCB in a vacuum bag is getting about 15 lb. per square inch clamping just from atmospheric pressure and a consistent pressure across the whole board. That should help level the epoxy assuming it is not too viscous. I absolutely agree with degassing the mixture and using a long pot life epoxy (30 minutes or more). The vacuum does not have to be applied for the whole 24 hour cure time, just until the epoxy is well set up and cannot reform bubbles. The pump plans at http://www.veneersupplies.com/ do include a filter before the pump to protect it from outgassing and moisture. They also have a pressure controlled switch so that the pump only runs when the vacuum falls to low. I built one. It was easy and it works great.

Regards,
Andrew

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 9:13 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,

As Andrew V. mentioned, vacuum bagging is an effective process for laminating. There are a couple of issues when using epoxy, or any resin that requires mixing. Mixing the resin and hardener introduces air bubbles into the epoxy. It is true that the vacuum will pull the air out, but a better way is to degas the resin before you apply it. Lots of descriptive material on the epoxy manufacturer's sites. The fly in the ointment is that the epoxy is curing while you are doing this. You need to use an epoxy with a relatively long pot life. Once the epoxy is degassed, you can apply it to your board and process in the vacuum bag. In both vacuum operations, it is important to have some kind of "filter" in the vacuum line to keep the volatiles that the vacuum pulls out of the epoxy out of the pump.Otherwise, the pump will eventually get gunked up with this material. A water bath might work, or a large chamber that slows down the flow to where the volatiles condense on the surfaces, rather than entering the pump.

Here is a reference to the degassing process: www.epotek.com/site/files/Techtips/pdfs/tip4.pdf

Another thing you should give a thought to, is how to produce an epoxy layer with a uniform thickness.

Harvey A.

On 7/18/2017 6:57 PM, 'Andrew Volk' amvweb@... [Homebrew_PCBs] wrote:

Brad –

Use a vacuum press. Vacuum is useful for many things, especially if you are also into woodworking (veneering), molding, etc. The vacuum will draw the bubbles out. Vacuum pumps are available from Harbor Freight. Just need a few fittings and a reinforced hose and a chamber or bag in which to put the boards. (See http://www.veneersupplies.com/pages/DIY__Vacuum__Press.html).

Andrew V.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 6:15 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

The material used to glue layers together in multilayer boards is called prepreg. I don’t see prepreg sold online anywhere though. Not even Ebay.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 7:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,
I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".
There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.
If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.
If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150°C. Others are lower, but then it will depend on what you can find.
I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.
Good luck in your search.
Harvey A.

On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-22 by Brad

Thanks for all the great responses. I guess I have a lot to think about now.

A question about temps – do I need to worry about fire risk, etc doing things this way? I mean, I would assume not so much an issue on a low voltage board, but on my TVT where an actual direct to AC connection is made and there’s a transformer..

The vacuum press idea sounds cool but might be beyond my skill level to assemble. I have a vacuum machine used for filling inkjets. It has a chamber about the side of a large coffee pot. I imagine for smaller stuff that would work. The larger boards though..

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 10:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

Harvey, Brad –

A PCB in a vacuum bag is getting about 15 lb. per square inch clamping just from atmospheric pressure and a consistent pressure across the whole board That should help level the epoxy assuming it is not too viscous. I absolutely agree with degassing the mixture and using a long pot life epoxy (30 minutes or more). The vacuum does not have to be applied for the whole 24 hour cure time, just until the epoxy is well set up and cannot reform bubbles. The pump plans at http://www.veneersupplies.com/ do include a filter before the pump to protect it from outgassing and moisture. They also have a pressure controlled switch so that the pump only runs when the vacuum falls to low. I built one. It was easy and it works great.

Regards,
Andrew

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 9:13 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,

As Andrew V. mentioned, vacuum bagging is an effective process for laminating. There are a couple of issues when using epoxy, or any resin that requires mixing. Mixing the resin and hardener introduces air bubbles into the epoxy. It is true that the vacuum will pull the air out, but a better way is to degas the resin before you apply it. Lots of descriptive material on the epoxy manufacturer's sites. The fly in the ointment is that the epoxy is curing while you are doing this. You need to use an epoxy with a relatively long pot life. Once the epoxy is degassed, you can apply it to your board and process in the vacuum bag. In both vacuum operations, it is important to have some kind of "filter" in the vacuum line to keep the volatiles that the vacuum pulls out of the epoxy out of the pump.Otherwise, the pump will eventually get gunked up with this material. A water bath might work, or a large chamber that slows down the flow to where the volatiles condense on the surfaces, rather than entering the pump.

Here is a reference to the degassing process: www.epotek.com/site/files/Techtips/pdfs/tip4.pdf

Another thing you should give a thought to, is how to produce an epoxy layer with a uniform thickness.

Harvey A.

On 7/18/2017 6:57 PM, 'Andrew Volk' amvweb@... [Homebrew_PCBs] wrote:

Brad –

Use a vacuum press. Vacuum is useful for many things, especially if you are also into woodworking (veneering), molding, etc. The vacuum will draw the bubbles out. Vacuum pumps are available from Harbor Freight. Just need a few fittings and a reinforced hose and a chamber or bag in which to put the boards. (See http://www.veneersuppliescom/pages/DIY__Vacuum__Press.html).

Andrew V.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 6:15 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

The material used to glue layers together in multilayer boards is called prepreg. I don’t see prepreg sold online anywhere though. Not even Ebay.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 7:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,
I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".
There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.
If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.
If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150°C. Others are lower, but then it will depend on what you can find.
I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.
Good luck in your search.
Harvey A.

On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

Virus-free. www.avg.com

Re: [Homebrew_PCBs] Attaching two PCBs together

2017-07-22 by Harvey Altstadter

Brad,

The vacuum press is not complicated. It is not really a press. We used a heavy duty silicone rubber bag that was designed for that purpose. I don't recommend that approach because the handling precautions associated with the silicone rubber are more than just annoying. Contact between the bag and the solderable surfaces rendered the boards unsolderable. Fingerprints can carry enough silicone to interfere with soldering. The website that Andrew included in his response has a section on vacuum bags that are made of more suitable materials. They also carry the bits and pieces that make it happen. These are not as durable and the silicone rubber bags, but then, you are not doing large scale production.

Harvey

On 7/22/2017 9:19 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

Thanks for all the great responses. I guess I have a lot to think about now.

A question about temps – do I need to worry about fire risk, etc doing things this way? I mean, I would assume not so much an issue on a low voltage board, but on my TVT where an actual direct to AC connection is made and there’s a transformer..

The vacuum press idea sounds cool but might be beyond my skill level to assemble. I have a vacuum machine used for filling inkjets. It has a chamber about the side of a large coffee pot. I imagine for smaller stuff that would work. The larger boards though..

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 10:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

Harvey, Brad –

A PCB in a vacuum bag is getting about 15 lb. per square inch clamping just from atmospheric pressure and a consistent pressure across the whole board That should help level the epoxy assuming it is not too viscous. I absolutely agree with degassing the mixture and using a long pot life epoxy (30 minutes or more). The vacuum does not have to be applied for the whole 24 hour cure time, just until the epoxy is well set up and cannot reform bubbles. The pump plans at http://www.veneersupplies.com/ do include a filter before the pump to protect it from outgassing and moisture. They also have a pressure controlled switch so that the pump only runs when the vacuum falls to low. I built one. It was easy and it works great.

Regards,
Andrew

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 9:13 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,

As Andrew V. mentioned, vacuum bagging is an effective process for laminating. There are a couple of issues when using epoxy, or any resin that requires mixing. Mixing the resin and hardener introduces air bubbles into the epoxy. It is true that the vacuum will pull the air out, but a better way is to degas the resin before you apply it. Lots of descriptive material on the epoxy manufacturer's sites. The fly in the ointment is that the epoxy is curing while you are doing this. You need to use an epoxy with a relatively long pot life. Once the epoxy is degassed, you can apply it to your board and process in the vacuum bag. In both vacuum operations, it is important to have some kind of "filter" in the vacuum line to keep the volatiles that the vacuum pulls out of the epoxy out of the pump.Otherwise, the pump will eventually get gunked up with this material. A water bath might work, or a large chamber that slows down the flow to where the volatiles condense on the surfaces, rather than entering the pump.

Here is a reference to the degassing process: www.epotek.com/site/files/Techtips/pdfs/tip4.pdf

Another thing you should give a thought to, is how to produce an epoxy layer with a uniform thickness.

Harvey A.

On 7/18/2017 6:57 PM, 'Andrew Volk' amvweb@... [Homebrew_PCBs] wrote:

Brad –

Use a vacuum press. Vacuum is useful for many things, especially if you are also into woodworking (veneering), molding, etc. The vacuum will draw the bubbles out. Vacuum pumps are available from Harbor Freight. Just need a few fittings and a reinforced hose and a chamber or bag in which to put the boards. (See http://www.veneersuppliescom/pages/DIY__Vacuum__Press.html).

Andrew V.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 6:15 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

The material used to glue layers together in multilayer boards is called prepreg. I don’t see prepreg sold online anywhere though. Not even Ebay.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 7:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,

I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".

There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.

If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.

If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150°C. Others are lower, but then it will depend on what you can find.

I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.

Good luck in your search.

Harvey A.

On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

Virus-free. www.avg.com

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-22 by Andrew Volk

Brad –

Two comments on vacuum. The key is the degree of vacuum you get is most important. Getting down to 20” Hg is good. Also, you don’t need a big chamber to degas the epoxy, just enough to hold the cup of mixture. As for the board lamination, a chamber is not the best idea anyway. A vacuum bag is better. That way you get the air pressure from outside for holding the pieces together while it cures.

I would think that the epoxy glue would not be a limiter for heat. A lot of epoxies will tell you what heat range they will tolerate. If it is getting that hot, the copper will likely lift.

Andrew

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Saturday, July 22, 2017 9:20 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

Thanks for all the great responses. I guess I have a lot to think about now.

A question about temps – do I need to worry about fire risk, etc doing things this way? I mean, I would assume not so much an issue on a low voltage board, but on my TVT where an actual direct to AC connection is made and there’s a transformer..

The vacuum press idea sounds cool but might be beyond my skill level to assemble. I have a vacuum machine used for filling inkjets. It has a chamber about the side of a large coffee pot. I imagine for smaller stuff that would work. The larger boards though..

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 10:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

Harvey, Brad –

A PCB in a vacuum bag is getting about 15 lb. per square inch clamping just from atmospheric pressure and a consistent pressure across the whole board That should help level the epoxy assuming it is not too viscous. I absolutely agree with degassing the mixture and using a long pot life epoxy (30 minutes or more). The vacuum does not have to be applied for the whole 24 hour cure time, just until the epoxy is well set up and cannot reform bubbles. The pump plans at http://www.veneersupplies.com/ do include a filter before the pump to protect it from outgassing and moisture. They also have a pressure controlled switch so that the pump only runs when the vacuum falls to low. I built one. It was easy and it works great.

Regards,
Andrew

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 9:13 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,

As Andrew V. mentioned, vacuum bagging is an effective process for laminating. There are a couple of issues when using epoxy, or any resin that requires mixing. Mixing the resin and hardener introduces air bubbles into the epoxy. It is true that the vacuum will pull the air out, but a better way is to degas the resin before you apply it. Lots of descriptive material on the epoxy manufacturer's sites. The fly in the ointment is that the epoxy is curing while you are doing this. You need to use an epoxy with a relatively long pot life. Once the epoxy is degassed, you can apply it to your board and process in the vacuum bag. In both vacuum operations, it is important to have some kind of "filter" in the vacuum line to keep the volatiles that the vacuum pulls out of the epoxy out of the pump.Otherwise, the pump will eventually get gunked up with this material. A water bath might work, or a large chamber that slows down the flow to where the volatiles condense on the surfaces, rather than entering the pump.

Here is a reference to the degassing process: www.epotek.com/site/files/Techtips/pdfs/tip4.pdf

Another thing you should give a thought to, is how to produce an epoxy layer with a uniform thickness.

Harvey A.

On 7/18/2017 6:57 PM, 'Andrew Volk' amvweb@... [Homebrew_PCBs] wrote:

Brad –

Use a vacuum press. Vacuum is useful for many things, especially if you are also into woodworking (veneering), molding, etc. The vacuum will draw the bubbles out. Vacuum pumps are available from Harbor Freight. Just need a few fittings and a reinforced hose and a chamber or bag in which to put the boards. (See http://www.veneersuppliescom/pages/DIY__Vacuum__Press.html).

Andrew V.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 6:15 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

The material used to glue layers together in multilayer boards is called prepreg. I don’t see prepreg sold online anywhere though. Not even Ebay.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 18, 2017 7:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Attaching two PCBs together

Brad,
I think you slipped a decimal point o the thickness of your boards- 0.031 and 0.0625".
There is another (better?) way, but it is problematical. You would get a much more uniform layer of adhesive by going with sheet adhesives. I my prior life, I was involved in some production that used sheet type adhesives to bond fairly big boards to heatsinks. The adhesive we used was an epoxy. I recall being able to buy sheet adhesives with or without a carrier layer, but since they were basically mixed, but uncured epoxy systems, they had to be kept in the freezer until use. The are other types of adhesives that also are available in sheet form. That was the good news. The bad news is that I couldn't find a place to buy these materials in reasonable quantities. I found an acrylic adhesive, recommended for this type of application, but it came on 3" rolls that were 250' long and 24" wide. Price was in the stratosphere. I looked at ebay, Amazon, McMaster-Carr and MSC to see if any of them carried these materials. Nada. A general Google search turned up some manufacturers, but no sellers at the retail level.
If you want to do your own search, look for sheet adhesives, adhesive preforms, bonding adhesive sheets.
If you should find a source, you will still be faced with the need to provide a fairly high, uniform pressure, and an elevated cure temperature. The material we used needed to withstand high temperatures, so we used something that cured over 150°C. Others are lower, but then it will depend on what you can find.
I did find some two sided adhesive mounting sheets at a craft store. No information available about what type of adhesive. They might work, but I am not so sure about how long they will stick, or if they might dry out.
Good luck in your search.
Harvey A.

On 7/18/2017 11:14 AM, 'Brad' unclefalter@... [Homebrew_PCBs] wrote:

So as I stated in a previous post, I have acquired some vintage 1973 PCB stock, which is perfect for a project I’m doing that replicates the 1973 TV Typewriter. Except for one thing – the stock is 0.31” thick, rather than 0.625”. So my thought was to epoxy two pieces together. And that works, except despite my best efforts, I end up with these ugly voids you can see. I’ve tried putting the boards under a press with heavy pressure but there’s always a few spots.

Is there a better way/adhesive to do this?

I realize it’d be easier to use 0.625” stock from the outset, but stock of the correct vintage just isn’t available, and it means a lot of me to be using actual boards from the time.

Thanks!!

Virus-free. www.avg.com

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-22 by Howard Chester

Hello Brad,

I have in the past used a 2 part adhesive from Hienkel. This method eliminates bubbles and high curing Tempratures

Unlike epoxy, the 2 part adhesive, each part is applied with a brush to each surface as a paint (one part to surface to top PCB and one part to the bottom surface).

Only a small amount of each is required to bond the treated surfaces together, vis; paint the surface, then use a smooth rubber squeegee to level the layer.

In this stage hold the top surface to the bottom surface edge to edge into the final position at an angle of approx 20-30 degrees and slowly "Roll" the surfaces together.

Clamp the surfaces in together a vice using a few bits of melamine board (high density chip board with plastic laminate, the stuff used in the kitchen and household furniture)

The required setting time is 30 mins, but I leave it for a few hours or overnight.

Heat is not a problem, this is evident by a touch test-about the same as a cooled cup of coffee

Hope this helps, chester.

PS if you are interested, I will look-up the product ref number

Re: Attaching two PCBs together

2017-07-23 by AncelB

Why don't you apply the chosen adhesive and run the thing thru a cold or
warm paper laminator a few times.

.

RE: [Homebrew_PCBs] Re: Attaching two PCBs together

2017-07-23 by K5ESS

You would have to find a way to maintain registration between the top and bottom and deal with the adhesive squeezed out in the process.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Saturday, July 22, 2017 10:19 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Re: Attaching two PCBs together

Why don't you apply the chosen adhesive and run the thing thru a cold or
warm paper laminator a few times.

.

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-24 by Brad

I would be interested in anything that simplifies the process. I looked up Henkel online but didn’t see the paint-on stuff you were mentioning. Any leads would be most welcome.

I don’t think I’ll be doing too many projects that demand actual vintage PCB stock – so I was hoping to avoid investing in a bunch of new equipment that may only see use a handful of times. Anything that can solve the bubbling issue without resorting to having to build machines, etc would be most welcome.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Saturday, July 22, 2017 4:48 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

Hello Brad,

I have in the past used a 2 part adhesive from Hienkel. This method eliminates bubbles and high curing Tempratures

Unlike epoxy, the 2 part adhesive, each part is applied with a brush to each surface as a paint (one part to surface to top PCB and one part to the bottom surface).

Only a small amount of each is required to bond the treated surfaces together, vis; paint the surface, then use a smooth rubber squeegee to level the layer.

In this stage hold the top surface to the bottom surface edge to edge into the final position at an angle of approx 20-30 degrees and slowly "Roll" the surfaces together.

Clamp the surfaces in together a vice using a few bits of melamine board (high density chip board with plastic laminate, the stuff used in the kitchen and household furniture)

The required setting time is 30 mins, but I leave it for a few hours or overnight.

Heat is not a problem, this is evident by a touch test-about the same as a cooled cup of coffee

Hope this helps, chester.

PS if you are interested, I will look-up the product ref number

Virus-free. www.avg.com

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-24 by mbushroe@...

There is a technique you can borrow from home built airplane builders. Vacuum bagging. Ideally, you would get the special perforated separator sheets, but you could do a test run with just what you would normally have at home,

Place the two boards together with what ever glue you want. I would use a two part epoxy possibly a slow cure to give you time to get everything right. A 5 minute epoxy would shorten the time the vacuum stays on. If hole line up between boards put wires through and then tape down the ends so that no sharp points stick out. The advantage to vacuum bagging is that flat, smooth, level surfaces are not needed, so the ends of the wires will not cause an problems. Then put the boards inside a plastic garbage bag and tape the open end around the hose from the vacuum. For a test run I don't think it matters if you use a home, rug vacuum or a shop vac. Smooth out the top and bottom layers of the bag where the boards are and start up the vacuum. It will press the boards together with considerable force, despite any irregularity in the board's surface. If you have a strong enough vac, it will suck the bubbles out of your glue to make a better,strong bond. You must leave the vacuum on until the adhesive has set. Then remove the vacuum, cut away the plastic and the boards should now be one. You do want to be careful not to put so much glue on that it squeezes out from between and sticks to the plastic bag. Putting a piece of waxed paper above and below the boards may help prevent that.

If it works well for you, they sell sheets of separator material that epoxy does not stick to. And a better, stronger vacuum pump that is intended for continuous duty would be obvious upgrades. I believe that most still use common trash bags for the smaller items (obviously doesn't work for whole wings!)

Mike

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-25 by roylowenthal@...

You really want to use a shop vac for that kind of work! Shop vacs have separate fans to keep the motor cooled while it's running - household vacs don't; they rely on the air flow thru the hose for motor cooling.

Adhesive squeeze out shouldn't be much of a problem with a polyethylene bag; they're almost impossible to glue anything to.

Roy

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-25 by Jeff Heiss

An aquarium air pump also works as a vacuum pump. It pulls a higher vacuum than a shop vac, quieter, and more convenient. I use one for photoresist vacuum bagging in a 12” x 12” bag and I would recommend it over a shop vac.

http://www.instructables.com/id/Vacuum-Pump-from-Aquarium-Air-Pump/

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Monday, July 24, 2017 9:31 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Attaching two PCBs together

You really want to use a shop vac for that kind of work! Shop vacs have separate fans to keep the motor cooled while it's running - household vacs don't; they rely on the air flow thru the hose for motor cooling.

Adhesive squeeze out shouldn't be much of a problem with a polyethylene bag; they're almost impossible to glue anything to.

Roy

Re: Attaching two PCBs together

2017-07-25 by Dave Sage

Dumb question:

If the boards you are gluing together are single sided boards don't you end up with either a double sided board OR a single sided board with a layer of copper in the middle (depending on which way you glue the boards together). If you end up with a layer of copper in the middle your leads going through the board are going to short out on the center copper layer. If you create a double sided board then that would not be true to the original - would it? Maybe I missed something. Either way gluing two boards together isn't going to look like the original. It seems you went to a lot of trouble to find the original board material all for not.

Re: [Homebrew_PCBs] Re: Attaching two PCBs together

2017-07-25 by Harvey White

On Tue, 25 Jul 2017 06:46:25 -0400, you wrote:

>Dumb question:
>
>If the boards you are gluing together are single sided boards don't you end
>up with either a double sided board OR a single sided board with a layer of
>copper in the middle (depending on which way you glue the boards together).

Yep.

>If you end up with a layer of copper in the middle your leads going through
>the board are going to short out on the center copper layer.

Nope. You create donuts around the feedthrough locations in the inner
layer. However, you've got no way of soldering them at all. Inside
layers work with plated through holes, and sometimes with homemade 4
layer boards, but it's awkward.

>If you create a
>double sided board then that would not be true to the original - would it?
>Maybe I missed something. Either way gluing two boards together isn't going
>to look like the original. It seems you went to a lot of trouble to find the
>original board material all for not.

you will get a board that looks indistinguishable from the thicker
material if you do it right. If the original board was single sided,
then you simply etch all the copper off one board and use it only as a
thickness builder.

You don't see the gap between the boards.

Harvey

RE: [Homebrew_PCBs] Re: Attaching two PCBs together

2017-07-25 by Brad

Tried the vacuum bag method with a thick contractor garbage bag. It did pull the bag taut against the boards but also sucked the bag a good way into the shop vac. Not sure if it was having the effect it should have. After letting it cure up a bit I checked but yeah, still large pockets of air.

I then tried simply putting a ton of epoxy on and spreading it around.. then kneading it out by hand. This actually worked best. I also made the bottom piece larger than the top. Here’s a pic of how it came out, next to an original Mark-8 board:

https://drive.google.com/file/d/0B4pq0-BHd2x6U29JNDlpTE1KNnM/view?usp=sharing

It doesn’t look that different in person.. the camera makes the Mark-8 board look much darker than it is. But there is a difference. Despite advertised as being ‘clear’, the epoxy does add a slight yellow tinge.

And yes, in this case what I did was etch one piece, and then actually for the second piece I took an etched piece that didn’t work out (that happens occasionally) etched the rest of the copper off and attached it. Good way to retrieve value from mistakes.

Brad

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 25, 2017 6:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: Attaching two PCBs together

On Tue, 25 Jul 2017 06:46:25 -0400, you wrote:

>Dumb question:
>
>If the boards you are gluing together are single sided boards don't you end
>up with either a double sided board OR a single sided board with a layer of
>copper in the middle (depending on which way you glue the boards together).

Yep.

>If you end up with a layer of copper in the middle your leads going through
>the board are going to short out on the center copper layer.

Nope. You create donuts around the feedthrough locations in the inner
layer. However, you've got no way of soldering them at all. Inside
layers work with plated through holes, and sometimes with homemade 4
layer boards, but it's awkward.

>If you create a
>double sided board then that would not be true to the original - would it?
>Maybe I missed something. Either way gluing two boards together isn't going
>to look like the original. It seems you went to a lot of trouble to find the
>original board material all for not.

you will get a board that looks indistinguishable from the thicker
material if you do it right. If the original board was single sided,
then you simply etch all the copper off one board and use it only as a
thickness builder.

You don't see the gap between the boards.

Harvey

Virus-free. www.avg.com

RE: [Homebrew_PCBs] Attaching two PCBs together

2017-07-26 by roylowenthal@...

I just did the experiment - a shop vac pulls about 3" Hg vacuum. Interesting because I've used it with a perforated board fixture to hold wooden things being routed.

Roy

RE: [Homebrew_PCBs] Re: Attaching two PCBs together

2017-07-26 by Tony Smith

You need a spacer between the boards and the bag, like Roy said in his last message.

The PCB needs to go between two flat boards (solid) larger than them, then something air can flow past. Usually you cut thin slots in the back of the flat boards.

Like this: http://www.joewoodworker.com/veneering/images/bag-explanation.gif

The idea is the two flat pieces will squish the PCB between them and any trapped air can get out the edges.

Still need to be careful that the halves don’t slip.

You can use those clothes storage vacuum bag things, they’re a fairly heavy gauge plastic.

Tony

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, 26 July 2017 3:14 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: Attaching two PCBs together

Tried the vacuum bag method with a thick contractor garbage bag. It did pull the bag taut against the boards but also sucked the bag a good way into the shop vac. Not sure if it was having the effect it should have. After letting it cure up a bit I checked but yeah, still large pockets of air.

I then tried simply putting a ton of epoxy on and spreading it around.. then kneading it out by hand. This actually worked best. I also made the bottom piece larger than the top. Here’s a pic of how it came out, next to an original Mark-8 board:

https://drive.google.com/file/d/0B4pq0-BHd2x6U29JNDlpTE1KNnM/view?usp=sharing

It doesn’t look that different in person.. the camera makes the Mark-8 board look much darker than it is. But there is a difference. Despite advertised as being ‘clear’, the epoxy does add a slight yellow tinge.

And yes, in this case what I did was etch one piece, and then actually for the second piece I took an etched piece that didn’t work out (that happens occasionally) etched the rest of the copper off and attached it. Good way to retrieve value from mistakes.

Brad

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 25, 2017 6:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: Attaching two PCBs together

On Tue, 25 Jul 2017 06:46:25 -0400, you wrote:

>Dumb question:
>
>If the boards you are gluing together are single sided boards don't you end
>up with either a double sided board OR a single sided board with a layer of
>copper in the middle (depending on which way you glue the boards together).

Yep.

>If you end up with a layer of copper in the middle your leads going through
>the board are going to short out on the center copper layer.

Nope. You create donuts around the feedthrough locations in the inner
layer. However, you've got no way of soldering them at all. Inside
layers work with plated through holes, and sometimes with homemade 4
layer boards, but it's awkward.

>If you create a
>double sided board then that would not be true to the original - would it?
>Maybe I missed something. Either way gluing two boards together isn't going
>to look like the original. It seems you went to a lot of trouble to find the
>original board material all for not.

you will get a board that looks indistinguishable from the thicker
material if you do it right. If the original board was single sided,
then you simply etch all the copper off one board and use it only as a
thickness builder.

You don't see the gap between the boards.

Harvey

Virus-free. www.avg.com

RE: [Homebrew_PCBs] Re: Attaching two PCBs together

2017-07-26 by Jeff Heiss

Felt works well to provide an air path in the bag. Without a porous material, the bag seals off at the vacuum tube connection preventing an evacuation. Try a layer of felt on the top and bottom of the board.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, July 26, 2017 2:39 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: Attaching two PCBs together

You need a spacer between the boards and the bag, like Roy said in his last message.

The PCB needs to go between two flat boards (solid) larger than them, then something air can flow past. Usually you cut thin slots in the back of the flat boards.

Like this: http://www.joewoodworker.com/veneering/images/bag-explanation.gif

The idea is the two flat pieces will squish the PCB between them and any trapped air can get out the edges.

Still need to be careful that the halves don’t slip.

You can use those clothes storage vacuum bag things, they’re a fairly heavy gauge plastic.

Tony

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, 26 July 2017 3:14 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: Attaching two PCBs together

Tried the vacuum bag method with a thick contractor garbage bag. It did pull the bag taut against the boards but also sucked the bag a good way into the shop vac. Not sure if it was having the effect it should have. After letting it cure up a bit I checked but yeah, still large pockets of air.

I then tried simply putting a ton of epoxy on and spreading it around.. then kneading it out by hand. This actually worked best. I also made the bottom piece larger than the top. Here’s a pic of how it came out, next to an original Mark-8 board:

https://drive.google.com/file/d/0B4pq0-BHd2x6U29JNDlpTE1KNnM/view?usp=sharing

It doesn’t look that different in person.. the camera makes the Mark-8 board look much darker than it is. But there is a difference. Despite advertised as being ‘clear’, the epoxy does add a slight yellow tinge.

And yes, in this case what I did was etch one piece, and then actually for the second piece I took an etched piece that didn’t work out (that happens occasionally) etched the rest of the copper off and attached it. Good way to retrieve value from mistakes.

Brad

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 25, 2017 6:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: Attaching two PCBs together

On Tue, 25 Jul 2017 06:46:25 -0400, you wrote:

>Dumb question:
>
>If the boards you are gluing together are single sided boards don't you end
>up with either a double sided board OR a single sided board with a layer of
>copper in the middle (depending on which way you glue the boards together).

Yep.

>If you end up with a layer of copper in the middle your leads going through
>the board are going to short out on the center copper layer.

Nope. You create donuts around the feedthrough locations in the inner
layer. However, you've got no way of soldering them at all. Inside
layers work with plated through holes, and sometimes with homemade 4
layer boards, but it's awkward.

>If you create a
>double sided board then that would not be true to the original - would it?
>Maybe I missed something. Either way gluing two boards together isn't going
>to look like the original. It seems you went to a lot of trouble to find the
>original board material all for not.

you will get a board that looks indistinguishable from the thicker
material if you do it right. If the original board was single sided,
then you simply etch all the copper off one board and use it only as a
thickness builder.

You don't see the gap between the boards.

Harvey

Virus-free. www.avg.com

RE: [Homebrew_PCBs] Re: Attaching two PCBs together

2017-07-26 by Tony Smith

Never tried felt, anything like that should be fine. I’ve seen people use mesh, like window mesh as well.

Of course you need to make sure the epoxy squeeze out doesn’t stick to whatever your using, melamine is common.

Tony

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, 26 July 2017 4:58 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: Attaching two PCBs together

Felt works well to provide an air path in the bag. Without a porous material, the bag seals off at the vacuum tube connection preventing an evacuation. Try a layer of felt on the top and bottom of the board.

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, July 26, 2017 2:39 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: Attaching two PCBs together

You need a spacer between the boards and the bag, like Roy said in his last message.

The PCB needs to go between two flat boards (solid) larger than them, then something air can flow past. Usually you cut thin slots in the back of the flat boards.

Like this: http://www.joewoodworker.com/veneering/images/bag-explanation.gif

The idea is the two flat pieces will squish the PCB between them and any trapped air can get out the edges.

Still need to be careful that the halves don’t slip.

You can use those clothes storage vacuum bag things, they’re a fairly heavy gauge plastic.

Tony

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, 26 July 2017 3:14 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: Attaching two PCBs together

Tried the vacuum bag method with a thick contractor garbage bag. It did pull the bag taut against the boards but also sucked the bag a good way into the shop vac. Not sure if it was having the effect it should have. After letting it cure up a bit I checked but yeah, still large pockets of air.

I then tried simply putting a ton of epoxy on and spreading it around.. then kneading it out by hand. This actually worked best. I also made the bottom piece larger than the top. Here’s a pic of how it came out, next to an original Mark-8 board:

https://drive.google.com/file/d/0B4pq0-BHd2x6U29JNDlpTE1KNnM/view?usp=sharing

It doesn’t look that different in person.. the camera makes the Mark-8 board look much darker than it is. But there is a difference. Despite advertised as being ‘clear’, the epoxy does add a slight yellow tinge.

And yes, in this case what I did was etch one piece, and then actually for the second piece I took an etched piece that didn’t work out (that happens occasionally) etched the rest of the copper off and attached it. Good way to retrieve value from mistakes.

Brad

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Tuesday, July 25, 2017 6:09 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: Attaching two PCBs together

On Tue, 25 Jul 2017 06:46:25 -0400, you wrote:

>Dumb question:
>
>If the boards you are gluing together are single sided boards don't you end
>up with either a double sided board OR a single sided board with a layer of
>copper in the middle (depending on which way you glue the boards together).

Yep.

>If you end up with a layer of copper in the middle your leads going through
>the board are going to short out on the center copper layer.

Nope. You create donuts around the feedthrough locations in the inner
layer. However, you've got no way of soldering them at all. Inside
layers work with plated through holes, and sometimes with homemade 4
layer boards, but it's awkward.

>If you create a
>double sided board then that would not be true to the original - would it?
>Maybe I missed something. Either way gluing two boards together isn't going
>to look like the original. It seems you went to a lot of trouble to find the
>original board material all for not.

you will get a board that looks indistinguishable from the thicker
material if you do it right. If the original board was single sided,
then you simply etch all the copper off one board and use it only as a
thickness builder.

You don't see the gap between the boards.

Harvey

Virus-free. www.avg.com