Homebrew PCBs

I'm about to make a microwave test PCB for the first time, using tone
transfer. The PCB size is about 4"x4" with the bottom layer is served
as a ground plane. How do I mask the bottom layer so the copper
remained intact during contact with ferric chloride? Vaseline? Masking
tape? Huge tip marking pen? Some kind of chemical etching resist?

TIA
Lanny

The easiest is adhesive tape, because it comes off in one piece and
you know it will resist.
But you must make sure to rub it on well, especially the edges.
You can overlap multiple strips of tape, but the junction is tricky to
get completely tight.
There are also wide rolls of this sticky plastic for protecting
schoolbooks from dirt.

Laquer also works, as long as you get a good continous layer. You
could use colophony resin dissolved in alcohol (used as a protective
coating/solder flux), or some other coating you might have around
anyway to coat your finished boards.

ST

On Wed, Jun 11, 2008 at 7:51 AM, lnphoenix <Lnphoenix@...> wrote:
> I'm about to make a microwave test PCB for the first time, using tone
> transfer. The PCB size is about 4"x4" with the bottom layer is served
> as a ground plane. How do I mask the bottom layer so the copper
> remained intact during contact with ferric chloride? Vaseline? Masking
> tape? Huge tip marking pen? Some kind of chemical etching resist?
>
> TIA
> Lanny
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

----- Original Message ----- 

From: "lnphoenix" <Lnphoenix@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, June 11, 2008 6:51 AM
Subject: [Homebrew_PCBs] How to mask bottom layer from etching?


> I'm about to make a microwave test PCB for the first time, using tone
> transfer. The PCB size is about 4"x4" with the bottom layer is served
> as a ground plane. How do I mask the bottom layer so the copper
> remained intact during contact with ferric chloride? Vaseline? Masking
> tape? Huge tip marking pen? Some kind of chemical etching resist?

Parcel tape works quite well.

Leon

--- In Homebrew_PCBs@yahoogroups.com, "lnphoenix" <Lnphoenix@...> wrote:
>
> I'm about to make a microwave test PCB for the first time, using tone
> transfer. The PCB size is about 4"x4" with the bottom layer is served
> as a ground plane. How do I mask the bottom layer so the copper
> remained intact during contact with ferric chloride? Vaseline? Masking
> tape? Huge tip marking pen? Some kind of chemical etching resist?
> 
> TIA
> Lanny
>

I use transparent contact paper (it's really not paper but a plastic), 
it's a lot easyer to remove than tape and does not seem to leave much 
residue behind. Get the kind that is normally used to line kitchen 
cabinets with. You just need to make sure the edges a well sealed to 
the PCB.

Hi Lanny,
I was just wondered what frequency you will be operating the microwave circuit, and what board you are using. As I understand it you can use FR4 up to 2GHz, beyond this you need special board which is made of a low-loss dielectric material. Also if you are using standard FR4, is there not a problem due to tolerances/variations associated with the board thickness over an area, as this will change the characteristic impedance of micro-strip lines - along the line (if you can see what I mean).

Cheers,

Gavin

lnphoenix <Lnphoenix@...> wrote:                             I'm about to make a microwave test PCB for the first time, using tone
 transfer. The PCB size is about 4"x4" with the bottom layer is served
 as a ground plane. How do I mask the bottom layer so the copper
 remained intact during contact with ferric chloride? Vaseline? Masking
 tape? Huge tip marking pen? Some kind of chemical etching resist?
 
 TIA
 Lanny
 
 
     
                                       

       

[Non-text portions of this message have been removed]

----- Original Message ----- 

From: "Gavin Dingley" <dingley76@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, June 11, 2008 6:05 PM
Subject: Re: [Homebrew_PCBs] How to mask bottom layer from etching?


> Hi Lanny,
> I was just wondered what frequency you will be operating the microwave 
> circuit, and what board you are using. As I understand it you can use FR4 
> up to 2GHz, beyond this you need special board which is made of a low-loss 
> dielectric material. Also if you are using standard FR4, is there not a 
> problem due to tolerances/variations associated with the board thickness 
> over an area, as this will change the characteristic impedance of 
> micro-strip lines - along the line (if you can see what I mean).

Radio amateurs often use FR4 above 2 GHz without any problems. Special 
dielectrics are only needed for high-performance applications.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND and FT-857D transceivers
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

Any kind of a laquer or enamil works well.  One I like for covering
large areas is just plain old nail polish. I just use the clear (get
crazy with colors if you like :-) ), it comes in really handy as the
paint brush is already in the bottle. Great for touching up large
areas where the toner couldn't handle and there's some pinholes. Also
nice for covering edges of the board. It really resists toner well.
And it's cheap (if I procure it when my wifes not home, it can
actually be free - hehe). Just kidding, I actually always have several
bottles around as it's great for setting trimmers, locking screws,
marking boards, color coding almost anything (connectors, wires, ect),
and sealing traces. And it works great as etchant resist (at least in
the Ferric Chloride, I think it would work in anything) It's harder to
remove, but not much worse than the toner itself (Laquer Thinner or
TRPS strips it right off). It might work well for sealing the edges of
the contact film too or seams in tape. 
Phil (KA0HBG)

> How do I mask the bottom layer so the copper
> remained intact during contact with ferric chloride? 
> Lanny
>

--- In Homebrew_PCBs@yahoogroups.com, Gavin Dingley <dingley76@...> wrote:
>
> Hi Lanny,
> I was just wondered what frequency you will be operating the
microwave circuit, and what board you are using. As I understand it
you can use FR4 up to 2GHz, beyond this you need special board which
is made of a low-loss dielectric material. Also if you are using
standard FR4, is there not a problem due to tolerances/variations
associated with the board thickness over an area, as this will change
the characteristic impedance of micro-strip lines - along the line (if
you can see what I mean).
> 
> Cheers,
> 
> Gavin
> 

FR4 can be used up to 4GHz if you reduce the size & the thickness of
the PCB. In addition to those Er's effect, the thickness of the PCB
affects the trace width and the size of the PCB affects the trace
length hence phase delay, loss etc. Above that 4 GHz, I plan to use
Rogers, Taconic materials. I try to mill the PCB before but my milling
machine doesn't have precision Z axis so I can't mill the thin PCB and
also it creates variable depth along the trace when removing copper
around the trace, causing me a lot of headaches.

I'm making test board to find out the most economical way to produce a
small size PCB for our small quantity purpose. I used to send out
simple board 1"x1" using Roger 4350 material and it costs $1000 to do
just that. I'm sure I can beat that $1000 cost per job.

Thanks guys for your inputs. I probably would try the adhesive tape
first and also the lacquer method later to see which one is best fit
for my situation. BTW, what is the trick to make sure that the edge is
sealed using adhesive tape?

Lanny

rub it down firmly with a cloth, for example.

Of course it is best to clean the copper first.

ST

On Wed, Jun 11, 2008 at 9:26 PM, lnphoenix <Lnphoenix@...> wrote:
> Thanks guys for your inputs. I probably would try the adhesive tape
> first and also the lacquer method later to see which one is best fit
> for my situation. BTW, what is the trick to make sure that the edge is
> sealed using adhesive tape?
>
> Lanny
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

----- Original Message ----- 

From: "lnphoenix" <Lnphoenix@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, June 11, 2008 8:26 PM
Subject: [Homebrew_PCBs] Re: How to mask bottom layer from etching?


> Thanks guys for your inputs. I probably would try the adhesive tape
> first and also the lacquer method later to see which one is best fit
> for my situation. BTW, what is the trick to make sure that the edge is
> sealed using adhesive tape?

Wrap it over the edge. It's best to make the board oversize and cut it to 
size after etching.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND and FT-857D transceivers
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

Another product you could try is bituminous paint. I used this as a
Ferric Chloride etch resist way back before obtaining my first Dalo pen. 

It comes off very easily with Mineral Turpentine, if a bit messy.

I feel it will be easier to work with than lacquer but less so than
adhesive tape or 'contact' book covering material.

Regards



"lnphoenix" wrote:

>
> .... I probably would try the adhesive tape
> first and also the lacquer method later...........
> 
> Lanny
>