Soldering of FPGAs

Hello,

Is it possible for a hobbyist to solder FPGAs with high pin counts to
PCBs? How would I go about doing it? What equipment would I need?

I want to starting working with FPGAs and rather than buying a development
board I wanted to build my own board gradually from scratch. Is this a
silly idea?

I've talked to some electrical repair people I know and they say its
impossible to solder chips with 200 pins or so without expensive kit. Is
this true? I could afford to spend maybe $100-$250 on some kit.

I've read some stuff, on the web, that seems to suggest that it is possible for a
hobbyist to solder FPGAs. What advice can you guys give?

Thanks very much,

Joel.

It is perfectly possible to solder and unsolder FPGAs (up to PQ208 or
similar) with fairly simple tools - good soldering iron, solder wick, and,
with my eyesight, a low power microscope. You can remove an fpga with a very
sharp scalpel blade (you will probably destroy the fpga in the process).

The real problem with FPGAs is the PCB. Most FPGAs are very high speed
devices and need a good ground plane and proper supply decoupling - without
these you will have endless problems. You should also bear in mind that
typical pin spacing is 0.65mm - translated this means 'very close' and very
fragile. It is very difficult to reliably attach wires directly to a device.
Making your own PCB for these purposes is not a job to be undertaken
lightly, particularly as you usually need at least 4 layers !

So, my advice would be - if you are learning, and do not have a specific
project in mind, buy one of the development/educational boards - believe me,
the reduction in hassle is well worth the extra cost ! There is also great
merit in starting from a known working state - debugging an FPGA board may
take more exotic equipment than you have hanging around. I have used Burched
boards www.burched.biz  , but there are quite a few others. When you have a
specific project in mind, and a bit more experience, then design your own
pcb - and find someone to make it for you.

Dave

"Joel Smith" <joels@mobyfoo.org> wrote in message
news:1071075419.16811.0@eunomia.uk.clara.net...
> Hello,
>
> Is it possible for a hobbyist to solder FPGAs with high pin counts to
> PCBs? How would I go about doing it? What equipment would I need?
>
> I want to starting working with FPGAs and rather than buying a development
> board I wanted to build my own board gradually from scratch. Is this a
> silly idea?
>
> I've talked to some electrical repair people I know and they say its
> impossible to solder chips with 200 pins or so without expensive kit. Is
> this true? I could afford to spend maybe $100-$250 on some kit.
>
> I've read some stuff, on the web, that seems to suggest that it is
possible for a
> hobbyist to solder FPGAs. What advice can you guys give?
>
> Thanks very much,
>
> Joel.

Hey Joel,

It is possible to solder TQFP/PQFP packages using a gold soldering iron and
bit of patience. Be sure do doulbe-check visually and electrically the board
before power-up.

There are also other methods. For example, take a look at this page (I have
not tried this method myself... yet):

http://www.seattlerobotics.org/encoder/200006/oven_art.htm

Regards,
-- Georgi



"Joel Smith" <joels@mobyfoo.org> wrote in message
news:1071075419.16811.0@eunomia.uk.clara.net...
> Hello,
>
> Is it possible for a hobbyist to solder FPGAs with high pin counts to
> PCBs? How would I go about doing it? What equipment would I need?
>
> I want to starting working with FPGAs and rather than buying a development
> board I wanted to build my own board gradually from scratch. Is this a
> silly idea?
>
> I've talked to some electrical repair people I know and they say its
> impossible to solder chips with 200 pins or so without expensive kit. Is
> this true? I could afford to spend maybe $100-$250 on some kit.
>
> I've read some stuff, on the web, that seems to suggest that it is
possible for a
> hobbyist to solder FPGAs. What advice can you guys give?
>
> Thanks very much,
>
> Joel.

>It is perfectly possible to solder and unsolder FPGAs (up to PQ208 or
>similar) with fairly simple tools - good soldering iron, solder wick, and,
>with my eyesight, a low power microscope. You can remove an fpga with a very
>sharp scalpel blade (you will probably destroy the fpga in the process).
>
>The real problem with FPGAs is the PCB. Most FPGAs are very high speed
>devices and need a good ground plane and proper supply decoupling - without
>these you will have endless problems. You should also bear in mind that
>typical pin spacing is 0.65mm - translated this means 'very close' and very
>fragile. It is very difficult to reliably attach wires directly to a device.
>Making your own PCB for these purposes is not a job to be undertaken
>lightly, particularly as you usually need at least 4 layers !

Your advice is perfectly ok, let me tell you though, that I'm
regularly fabricating my own four layer PCB's at home. To produce a
four layer PCB 3x3" in size takes about 4 hours. Such a PCB costs me
then ~$10 so provided you need some of them over time it's IMHO well
worth the effort. That's especially true for prototyping and advanced
hobbyist use. My main motivation was that I really got sick of waiting
for the boardhouse to complete the PCB. I know that in some areas it's
much easier to get cheap and quick PCB's, but four hours are IMHO hard
to beat! :-)) If you consider the fact that where I live getting a
four layer PCB of said size in say three workign days costs a fortune
($2K!!!!) it really makes sense.

Six layer is also possible just means more work (add two hours for
above sample PCB). So, if one is dedicated enough it can be done. The
main requirement is having a through hole plating station. I built one
myself. Those which are interested might want to visit

www.myhome.ch/mzingg/pcbstuff/tps 

Soldering BGA's is trickey but even here are (rare) "homebrew"
solutions around. I'm curently experimenting in this area and hope to
have this working for myself soon.

Please note that this is strictly for my personal needs / prototyping
work. That said it's clear that even for small production runs I'm
more than happy to use the services of a board house.

Markus

Joel,
    It is possible, but not advisable. The finer the pin, the lower the
total heat time is. Also the probability of solder balls and shorts is
greater. Certain vendors sell development boards with mounted FPGA's pinned
out to berg connectors and some to MIC connectors. It's safer this way and
less agravation, also it addresses noise and power decoupling issues.

Soldering by hand works.  Investment in micro-width solder and solder-wick
are only part of the journey.  I can do this kind of work easily under a
stereo microscope but I imagine a hobbyist may not have one handy and they
tend to be more than $100-$250.  Perhaps jewelers' magnifiers (the glasses
with the lenses on swing-in arms) could suffice but personally, I don't want
to get my face too close to boiling rosin.

Tacking down opposite corner pins for an alignment check around all four
sides is a good start, allowing a slight skew to be corrected before going
too far down a wrong path.  With those corners in place, the trick is to get
good solder flow without wicking to the adjacent pad.  It's tough but can be
fun.

"Georgi Beloev" <gbH8SPAM@beloev.net> wrote in message
news:vteoqe7hkto707@corp.supernews.com...
> Hey Joel,
>
> It is possible to solder TQFP/PQFP packages using a gold soldering iron
and
> bit of patience. Be sure do doulbe-check visually and electrically the
board
> before power-up.
>
> There are also other methods. For example, take a look at this page (I
have
> not tried this method myself... yet):
>
> http://www.seattlerobotics.org/encoder/200006/oven_art.htm
>
> Regards,
> -- Georgi
>
>
>
> "Joel Smith" <joels@mobyfoo.org> wrote in message
> news:1071075419.16811.0@eunomia.uk.clara.net...
> > Hello,
> >
> > Is it possible for a hobbyist to solder FPGAs with high pin counts to
> > PCBs? How would I go about doing it? What equipment would I need?
> >
> > I want to starting working with FPGAs and rather than buying a
development
> > board I wanted to build my own board gradually from scratch. Is this a
> > silly idea?
> >
> > I've talked to some electrical repair people I know and they say its
> > impossible to solder chips with 200 pins or so without expensive kit. Is
> > this true? I could afford to spend maybe $100-$250 on some kit.
> >
> > I've read some stuff, on the web, that seems to suggest that it is
> possible for a
> > hobbyist to solder FPGAs. What advice can you guys give?
> >
> > Thanks very much,
> >
> > Joel.
>
>

The easiest part to solder is a BGA.  You line it up on the pads and to keep
it from sliding during reflow you must glue some sort of "corral" around it;
I've used SMT resistors for this.  Then you just heat it up with one of
those big red hot air guns that look like oversized hair dryers that would
fry a hole in your scalp  (I think these are around $100.)  I've done this
with success.  You may have to put solder or paste on the pads if there is
none on the PCB already.
-Kevin

"Joel Smith" <joels@mobyfoo.org> wrote in message
news:1071075419.16811.0@eunomia.uk.clara.net...
> Hello,
>
> Is it possible for a hobbyist to solder FPGAs with high pin counts to
> PCBs? How would I go about doing it? What equipment would I need?
>
> I want to starting working with FPGAs and rather than buying a development
> board I wanted to build my own board gradually from scratch. Is this a
> silly idea?
>
> I've talked to some electrical repair people I know and they say its
> impossible to solder chips with 200 pins or so without expensive kit. Is
> this true? I could afford to spend maybe $100-$250 on some kit.
>
> I've read some stuff, on the web, that seems to suggest that it is
possible for a
> hobbyist to solder FPGAs. What advice can you guys give?
>
> Thanks very much,
>
> Joel.

If you really want to solder a fine pitch IC - Get a Metcal soldering iron
(or borrow one)



"Amos B. Moses" <nospam@nospam.com> wrote in message
news:qOKBb.35636$ue2.6262@newssvr32.news.prodigy.com...
> Joel,
>     It is possible, but not advisable. The finer the pin, the lower the
> total heat time is. Also the probability of solder balls and shorts is
> greater. Certain vendors sell development boards with mounted FPGA's
pinned
> out to berg connectors and some to MIC connectors. It's safer this way and
> less agravation, also it addresses noise and power decoupling issues.
>
>
>

I found that soldering SMDs (including TQFPs and PQFPs) is easy, as long as
you have flux handy.
Tweezers and a magnifier can also be useful.
Jean

more advices here:
http://www.fpga4fun.com/forum/viewtopic.php?t=6


"Joel Smith" <joels@mobyfoo.org> wrote in message
news:1071075419.16811.0@eunomia.uk.clara.net...
> Hello,
>
> Is it possible for a hobbyist to solder FPGAs with high pin counts to
> PCBs? How would I go about doing it? What equipment would I need?
>
> I want to starting working with FPGAs and rather than buying a development
> board I wanted to build my own board gradually from scratch. Is this a
> silly idea?
>
> I've talked to some electrical repair people I know and they say its
> impossible to solder chips with 200 pins or so without expensive kit. Is
> this true? I could afford to spend maybe $100-$250 on some kit.
>
> I've read some stuff, on the web, that seems to suggest that it is
possible for a
> hobbyist to solder FPGAs. What advice can you guys give?
>
> Thanks very much,
>
> Joel.

"Joel Smith" <joels@mobyfoo.org> wrote in message
news:1071075419.16811.0@eunomia.uk.clara.net...
> Hello,
>
> Is it possible for a hobbyist to solder FPGAs with high pin counts to
> PCBs? How would I go about doing it? What equipment would I need?
>
> I want to starting working with FPGAs and rather than buying a development
> board I wanted to build my own board gradually from scratch. Is this a
> silly idea?
>
> I've talked to some electrical repair people I know and they say its
> impossible to solder chips with 200 pins or so without expensive kit. Is
> this true? I could afford to spend maybe $100-$250 on some kit.
>
> I've read some stuff, on the web, that seems to suggest that it is
possible for a
> hobbyist to solder FPGAs. What advice can you guys give?
>

The method I used to do for PQ208s and such was to make my PCBs with
lead&tin coating. Now, all what I needed to do was to glue the PQ208 part in
its place, and use hot air on the pins. Less than 2 minutes for a perfect
job.