Homebrew_PCBs

hello

Well my pcb first pcb etching has worked a treat.

i now have a board ready to poulate. i have designed a board that
has surface mount components.

I have soldered surface mount before but only when there is a resist layer present. At the moment I do not have access to any resist.


I have found a supplier of resist film but it wont be with me in time.

interestingly I have seen an article on making solder paste stencils from aluminium coke cans using the toner transfer method and etching.....Can you see where this is going?

Is it possible to use solder paste or to use the reflow method to solder without a resist layer?

Thanks
Charlie

I do it all the time. There are many tutorials out there, but I
usually use solder paste hand delivered. Any excess can be removed
with solder wick after reflowing. I have also made stencils using a
piece of very thin copperclad (7 mil or so) and drilling small holes
over the pads. Place the stencil on the pcb, smear solder paste over
it, then remove stencil and place parts.

Mark


At 04:53 PM 2/14/2013, you wrote:

>hello
>
>Well my pcb first pcb etching has worked a treat.
>
>i now have a board ready to poulate. i have designed a board that
>has surface mount components.
>
>I have soldered surface mount before but only when there is a resist
>layer present. At the moment I do not have access to any resist.
>
>
>I have found a supplier of resist film but it wont be with me in time.
>
>interestingly I have seen an article on making solder paste stencils
>from aluminium coke cans using the toner transfer method and
>etching.....Can you see where this is going?
>
>Is it possible to use solder paste or to use the reflow method to
>solder without a resist layer?
>
>Thanks
>Charlie
>
>
>
>------------------------------------
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
>http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>

El 14/02/13 21:53, scubadogct escribió:

> I have soldered surface mount before but only when there is a resist layer present. At the moment I do not have access to any resist.
>

It's not really a problem.

I've hand soldered 0.4mm pitch LQFPs on a home made board without solder
resist. (Making the board with that fine pitch was a far bigger trial
than soldering the chip to it). Solder wick and flux are your best friends.

After many detours using solder paste, stencils, hot air etc. I've come
to the conclusion that I can solder SMD faster and more neatly with a
soldering iron. I've found using some kapton tape to hold the part in
position, and use plenty of flux from a flux dispensing pen before
soldering gives very good results and it's easy to do, since getting the
part positioned by taping it down is easier than trying to tack corners
on any of the packages with pins on all 4 sides.

Maybe an aluminum pie pan would work also for the stencil.



Jeff





_____

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
On Behalf Of Mark Lerman
Sent: Thursday, February 14, 2013 5:38 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] soldering surface mount without solder resist.





I do it all the time. There are many tutorials out there, but I
usually use solder paste hand delivered. Any excess can be removed
with solder wick after reflowing. I have also made stencils using a
piece of very thin copperclad (7 mil or so) and drilling small holes
over the pads. Place the stencil on the pcb, smear solder paste over
it, then remove stencil and place parts.

Mark

At 04:53 PM 2/14/2013, you wrote:

>hello
>
>Well my pcb first pcb etching has worked a treat.
>
>i now have a board ready to poulate. i have designed a board that
>has surface mount components.
>
>I have soldered surface mount before but only when there is a resist
>layer present. At the moment I do not have access to any resist.
>
>
>I have found a supplier of resist film but it wont be with me in time.
>
>interestingly I have seen an article on making solder paste stencils
>from aluminium coke cans using the toner transfer method and
>etching.....Can you see where this is going?
>
>Is it possible to use solder paste or to use the reflow method to
>solder without a resist layer?
>
>Thanks
>Charlie
>
>
>
>------------------------------------
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
>http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>

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

On Fri, Feb 15, 2013 at 11:01 AM, Dylan Smith <dyls@...> wrote:

> El 14/02/13 21:53, scubadogct escribió:
>> I have soldered surface mount before but only when there is a resist layer present. At the moment I do not have access to any resist.
>>
> It's not really a problem.

Seconded. For fine pitch, flux helps a lot.

> I've hand soldered 0.4mm pitch LQFPs on a home made board without solder

If you get a board made commercially with a 0.4mm pitch footprint,
often the soldermask will not survive anyway.

http://i.imgur.com/n4z5PCP.jpg

> I've found using some kapton tape to hold the part in position,

A mini-gardening fork also works well :-)

http://4.bp.blogspot.com/-N1k6OM8C8cs/Te8whMyqdQI/AAAAAAAAACQ/wPkrIs_FRcM/s1600/IMG_6288r.JPG

Mitch.

Well I used solder paste and a frying pan as
a make shift reflow plate.

All worked easily.

Only 1 bridge on an IC pin.

I am a convert to sufrace mount and reflow!

Soldering fine-pitch ICs is a bit easier if you plan ahead and make the
copper pads on your PCB stick out a bit more than usual. This gives you
a way to wick excess solder away from the chip.

Other than that, Like others said, use a regular soldering iron. Put
too much solder on at first, then wick off the extra with copper braid.
Use lots of flux. It's pretty quick and easy to do. The only time this
doesn't work is if you have signals that are very high impedance, where
the excess flux might cause too much current to flow between pins. For
those cases, you really do need to use a stencil and reflow and get it
"just right" so that the reflow burns off all (ha!) of the flux.

Even with a paste stencil you're going to get shorts occasionally.
Learn how to quickly fix them ;-)

Also, for fine pitch parts, the solder mask usually doesn't fit between
the pins anyway due to fab spacing rules, so it's not going to help you.
Most of my fab'd boards have no mask between pins on QFPs et al.

>>>". . . . Use lots of flux. It's pretty quick and easy to do. The only

time this doesn't work is if you have signals that are very high impedance,
where the excess flux might cause too much current to flow between pins. .
. . ">>>

I always clean off flux, no matter what. I use alcohol (any kind) and a
soft tooth brush. I don't like the look of uncleaned flux, and there's no
chance of high impedance cross talk if there's no flux there.

Todd, K7TFC

On Feb 15, 2013 7:48 PM, "DJ Delorie" <dj@...> wrote:

> **
>
>
>
> Soldering fine-pitch ICs is a bit easier if you plan ahead and make the
> copper pads on your PCB stick out a bit more than usual. This gives you
> a way to wick excess solder away from the chip.
>
> Other than that, Like others said, use a regular soldering iron. Put
> too much solder on at first, then wick off the extra with copper braid.
> Use lots of flux. It's pretty quick and easy to do. The only time this
> doesn't work is if you have signals that are very high impedance, where
> the excess flux might cause too much current to flow between pins. For
> those cases, you really do need to use a stencil and reflow and get it
> "just right" so that the reflow burns off all (ha!) of the flux.
>
> Even with a paste stencil you're going to get shorts occasionally.
> Learn how to quickly fix them ;-)
>
> Also, for fine pitch parts, the solder mask usually doesn't fit between
> the pins anyway due to fab spacing rules, so it's not going to help you.
> Most of my fab'd boards have no mask between pins on QFPs et al.
>
>


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

"Todd F. Carney" <k7tfc@...> writes:

> I always clean off flux, no matter what. I use alcohol (any kind) and a
> soft tooth brush. I don't like the look of uncleaned flux, and there's no
> chance of high impedance cross talk if there's no flux there.

Me too, but under fine pitch parts or between closely spaced pins, you
might not have a choice.