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'[EE] SMT on homemade pcbs'
2005\03\22@092432 by Daniel Chia

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face
Hi,
       With so many nice chips only available in fine pitch(0.5mm) QFP
/ LQFP / TQFP packaging, I was just wondering whether it is actually
feasible to do such chips on a home made pcb or is it just wishful
thinking on my part..

------------------------------------------------------------------------
Daniel Chia

"Genius is one percent inspiration and ninety-nine percent
perspiration."

    - Thomas Edison

E-mail: spam_OUTdanielcjhTakeThisOuTspamyahoo.com.sg
MSN: .....danstryder01KILLspamspam@spam@yahoo.com.sg
ICQ: 37878331
------------------------------------------------------------------------




2005\03\22@095043 by Josh Koffman

face picon face
I've done it. It's not super easy, and you have to be really anal
about getting the etch resist looking right before you actually etch.
I'd reccomend sending your boards away to a place like AP Circuits
(http://www.apcircuits.com) or one of the other board houses to ensure
you have nice traces. If you use a service like Olimex you'll also get
solder mask which is _very_ helpful when trying to solder. Guessing
that you're from .sg, these may not be the most feasable, but there
should be someone locally to help you!

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

On Tue, 22 Mar 2005 22:27:35 +0800, Daniel Chia <danielcjhspamKILLspamyahoo.com.sg> wrote:
>         With so many nice chips only available in fine pitch(0.5mm) QFP
> / LQFP / TQFP packaging, I was just wondering whether it is actually
> feasible to do such chips on a home made pcb or is it just wishful
> thinking on my part..

2005\03\22@095453 by alan smith

picon face
Steady hand....good temperature controlled iron
w/small tip and good eyes or a scope.  0201 packages
give me grief tho

I think the biggest issue is the quality of the board
itself.  You NEED solder mask else asking for trouble.


--- Daniel Chia <.....danielcjhKILLspamspam.....yahoo.com.sg> wrote:
> Hi,
>        With so many nice chips only available in fine
> pitch(0.5mm) QFP
> / LQFP / TQFP packaging, I was just wondering
> whether it is actually
> feasible to do such chips on a home made pcb or is
> it just wishful
> thinking on my part..
>
>
------------------------------------------------------------------------
{Quote hidden}

------------------------------------------------------------------------
>
>
>
>
> --

2005\03\22@100714 by ThePicMan

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At 22.27 2005.03.22 +0800, you wrote:
>Hi,
>        With so many nice chips only available in fine pitch(0.5mm) QFP
>/ LQFP / TQFP packaging, I was just wondering whether it is actually
>feasible to do such chips on a home made pcb or is it just wishful
>thinking on my part..

I do, double sided. I have a laser printer (an old 600 dpi Epson); a
home made contact printer; a Dremel (helps with the vias); and a lot
of experience and fine tuning.
I think you can forget it without a laser printer, though. I've just
bought (ordered) an HP LJ 1300, but haven't tested it yet. Things should
even improve with it, I hope (i.e. I will get more good PCBs per wafer).
Well worth for prototyping (but not for production, neither small-scale.
For that there are companies like Olimex).

2005\03\22@103111 by Hulatt, Jon
picon face
I've not done that small, but I had no troubles with my home-fabbed
FT232BM board* . The FT232 isn't quite as small as your 0.5mm stuff-
0.8mm lead pitch, 0.4mm lead/trace width. I've not tried anything
smalled. My eyesight is not very good, so I find the soldering very very
hard. I tend to pick bigger components where possible.

* no troubles is a blatant lie. Although the traces came out nice, and
the chip soldered well, I forgot some of the power supply pins so it
didn't work. oops.


Thanks

Jon

{Quote hidden}

2005\03\22@103649 by Mike Harrison

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On Tue, 22 Mar 2005 22:27:35 +0800, you wrote:

>Hi,
>        With so many nice chips only available in fine pitch(0.5mm) QFP
>/ LQFP / TQFP packaging, I was just wondering whether it is actually
>feasible to do such chips on a home made pcb or is it just wishful
>thinking on my part..

Doable but can be tricky. For home-etched PCBs, tin-plating helps a lot.
I've done homebrew PCBs with 0.5mm TSOPs. The biggest problem is not soldering, but through-linking
under packages.
Lots of info at http://www.electricstuff.co.uk/pcbs.html

The best aid to vision is a very bright light.


2005\03\22@113501 by Herbert Graf

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On Tue, 2005-03-22 at 22:27 +0800, Daniel Chia wrote:
> Hi,
>        With so many nice chips only available in fine pitch(0.5mm) QFP
> / LQFP / TQFP packaging, I was just wondering whether it is actually
> feasible to do such chips on a home made pcb or is it just wishful
> thinking on my part..

Certainly possible. Making the PCB will be the easy part, it'll be
soldering the part onto your PCB without a solder mask that will be
difficult.

I did it with a 22 pin connector with 0.5mm pitch, a microscope is
necessary IMHO. If I had to do it again I would certainly send it out to
a board house. TTYL


-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

2005\03\22@113642 by Herbert Graf

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On Tue, 2005-03-22 at 16:05 +0100, ThePicMan wrote:
> At 22.27 2005.03.22 +0800, you wrote:
> >Hi,
> >        With so many nice chips only available in fine pitch(0.5mm) QFP
> >/ LQFP / TQFP packaging, I was just wondering whether it is actually
> >feasible to do such chips on a home made pcb or is it just wishful
> >thinking on my part..
>
> I do, double sided. I have a laser printer (an old 600 dpi Epson); a
> home made contact printer; a Dremel (helps with the vias); and a lot
> of experience and fine tuning.
> I think you can forget it without a laser printer, though.

Why would you say that? I haven't bumped into any problems using my ink
jet, as long as you get transparencies meant for ink-jets everything
works fine. TTYL


-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

2005\03\22@115308 by Hulatt, Jon

picon face
To add some pointers that are only partly related to this-
 
My most recent homemade board, I used 90gsm tracing paper instead of a
plastic transparency. Although it doesn't look particularly transparent
when compared to the plastic, it's good enough. I found exposure time
needed to be about 20% longer than with transparency.

But the real magic is that the tracing paper holds its charge better, so
you get real solid blacks and much finer lines. That, coupled with the
fact that it's much much cheaper, and i'm not looking back.

Jon

> {Original Message removed}

2005\03\23@035934 by ThePicMan

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At 11.36 2005.03.22 -0500, you wrote:
>On Tue, 2005-03-22 at 16:05 +0100, ThePicMan wrote:
>> At 22.27 2005.03.22 +0800, you wrote:
>> >Hi,
>> >        With so many nice chips only available in fine pitch(0.5mm) QFP
>> >/ LQFP / TQFP packaging, I was just wondering whether it is actually
>> >feasible to do such chips on a home made pcb or is it just wishful
>> >thinking on my part..
>>
>> I do, double sided. I have a laser printer (an old 600 dpi Epson); a
>> home made contact printer; a Dremel (helps with the vias); and a lot
>> of experience and fine tuning.
>> I think you can forget it without a laser printer, though.
>
>Why would you say that? I haven't bumped into any problems using my ink
>jet, as long as you get transparencies meant for ink-jets everything
>works fine. TTYL

"fine pitch(0.5mm) QFP" ?

2005\03\23@035942 by ThePicMan

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face
At 16.53 2005.03.22 +0000, you wrote:
>To add some pointers that are only partly related to this-
>  
>My most recent homemade board, I used 90gsm tracing paper instead of a
>plastic transparency. Although it doesn't look particularly transparent
>when compared to the plastic, it's good enough. I found exposure time
>needed to be about 20% longer than with transparency.
>
>But the real magic is that the tracing paper holds its charge better, so
>you get real solid blacks and much finer lines. That, coupled with the
>fact that it's much much cheaper, and i'm not looking back.

I always use only tracing paper, and fully agree with all your points.

2005\03\23@103835 by Dal Wheeler

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This isn't too bad to do.  The page below shows some boards doing just
that.  These were done a couple of years ago on a HP5L.  I've got a 1300
that does a nicer job now.

For soldering the IC's I use a good soldering iron, brush on water base
flux and organic flux solder.  Tack down the corners of the component
and drag a bead of solder accross the pins -- allow the flux to do its
job.  no need to get a microscope and solder each pin individually.  
Clean up any bridging you might have with solder wick copper braid.  
With practice you don't have much cleanup to do.  

For soldering chip resistors/caps I use water soluble solder paste and a
cheap hot air pencil.

http://myweb.cableone.net/wheedal/pcb.htm
This describes using toner transfer with magazine paper stock --click on
pictures to see detail.

myweb.cableone.net/wheedal/pcbconstruct/cpu3_7b.jpg
The problem with this cpu board was all the darn drilling.  The 32pin
tsop was irritating --I ended up getting a little too carried away with
the soldering iron and pulled up a trace --repaired with fine wirewrap
wire.  Lots of water soluble flux helps.

-Dal


Daniel Chia wrote:

>        With so many nice chips only available in fine pitch(0.5mm) QFP
>/ LQFP / TQFP packaging, I was just wondering whether it is actually
>feasible to do such chips on a home made pcb or is it just wishful
>thinking on my part..
>  
>

2005\03\23@105842 by Herbert Graf

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part 1 1778 bytes content-type:text/plain (decoded 7bit)

On Wed, 2005-03-23 at 08:50 +0100, ThePicMan wrote:
> >Why would you say that? I haven't bumped into any problems using my ink
> >jet, as long as you get transparencies meant for ink-jets everything
> >works fine. TTYL
>
> "fine pitch(0.5mm) QFP" ?

Yup. I don't really see WHY there would be a difference between laser
and ink jet in this area. About the only issue I could see is whether
inkjet ink is transparent to UV. In the case of my ink jet it appears
it's not since I got a very good result with 0.5mm pitch pins.

The connector I made a board for with my inject was this one:

digikey part number: HFJ22CT-ND

rocky.digikey.com/scripts/ProductInfo.dll?
Site=CA&V=26&M=FH12-22S-0.5SH

The exposure and developing turned out very well. The etching OTOH
didn't go that great, the etchant I was using was kinda old, so it
didn't work to well anymore. To prevent undercutting I etched for a
shorter time then I wanted, which meant going over the board with a
microscope to check for adjacent traces touching. In the end two were
touching, quick work with an exacto knife and I was done.

Soldering wasn't fun considering I had no solder mask, but in the end it
did end up working out OK.

I've attached two pictures of the board I made. I know it looks like the
lines are touching, but that's due to the rescaling and JPG compression
I needed to do to get the image small enough to post. Trust me when I
say that the lines aren't touching... :) The board works BTW, it was
alot of work, and it's because of that effort that the next time I want
a board, I'll send it to a board house...

TTYL

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/


part 2 28585 bytes content-type:image/jpeg; name=board_display.jpg (decode)


part 3 9408 bytes content-type:image/jpeg; name=mask.jpg (decode)


part 4 35 bytes content-type:text/plain; charset="us-ascii"
(decoded 7bit)

2005\03\23@114121 by Hulatt, Jon

picon face
if anyone is interested, pictures of some of the most recent boards i've
made are here:- www.slippyr4.com/Category.aspx?category=consult
although they don't include any smt stuff. also info about my current
pic project, if you're interested. it's car related.

> {Original Message removed}

2005\03\23@130336 by William Chops Westfield

face picon face
On Mar 23, 2005, at 7:38 AM, Dal Wheeler wrote:

>>        With so many nice chips only available in fine pitch(0.5mm) QFP
>> / LQFP / TQFP packaging, I was just wondering whether it is actually
>> feasible to do such chips on a home made pcb

There are a couple of issues I've seen beyond being able to create
the PCB and solder the components to it.

1) lack of plated through vias.  vias become a near-necessity with
   fine pitch packages, and not having them plated through is a
   major PITA with home-fabricated PCBs.

2) Only two layers.  Some of the chips being made today seem to
   assume they'll end up on a 4-layer board with nice ground and
   power planes.  For instance, I've been playing with a PCB for
   one of the 64pin ARMs.  It has essentially a power and ground
   on each edge of the package, and I can't figure out a way to
   get all the power connected and still have the rest of the
   pins routable in only two layers.

(1 and 2 trade off against one another; you can probably solve
the power routing issue with enough vias...)

Now, if you have a 64pin LQFP and only need to connect a fraction
of the pins to anything, that might be doable, and I think I can
see situations where that might be useful.  But for cases where
you need to use the majority of the pins, I think home PCBs are
increasingly impractical...

BillW

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