Soldering of FPGAs

[Joel Smith]

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.

 

[Dave Garnett]

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.

 

[Georgi Beloev]

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.

 

[Markus Zingg]

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

 

[Amos B. Moses]

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.

 

[John_H]

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.

 

[Kevin Neilson]

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.

 

[NJ]

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.

 

[Jean Nicolle]

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.

 

[Arash Salarian]

"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.

 

[Nial Stewart]

John_H <johnhandwork@mail.com> wrote in message
news:1GLBb.9$Ej2.1783@news-west.eli.net...

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.

If you keep an eye on auctions you might be able to
pick one up for this sort of money.

An example is

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=2580122938&category=361


Nial

------------------------------------------------
Nial Stewart Developments Ltd
FPGA and High Speed Digital Design
www.nialstewartdevelopments.co.uk

 

[NJ]

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.

thats a good idea!

 

[Hal Murray]

Making your own PCB for these purposes is not a job to be undertaken
lightly, particularly as you usually need at least 4 layers !

Just for reference...

It may not be too expensive to have a 4 layer board made commercially.

I've used PCB Express - www.pcbexpress.com. There are several similar
sites. 4 boards, 20 sq inches, 4 layers, no silk screen or solder mask
is $183. $274 gets top side screen/mask. $45 more for bottom.

They are non-fancy design rules: 7/7. That's probably good enough
for hobby type projects.

You do need access to board design tools and how to use them.

Then you still have the problem that started this thread.

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.

 

[Jon Elson]

Joel Smith wrote:

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?


Yes. You'd better have pretty good eyes and steady hands.

I am currently installing Xilinx XCS30TQ144 chips on a small production
product, that is the .5 mm lead pitch package. I use solder paste,
which I got in a 35 gm
syringe. You will need to beg, borrow or steal (just kidding) needles
around
20 gauge. I cut them off fairly short, and then round the end off on a
sharpening
stone so it is relatively free of scratchy edges and has a 30 degree or
so slant
on the end. You place the thinnest bead of solder paste on the outer
edge of
the solder pads on the PCB. You then position the chip with angled tweezers
and solder one corner lead, while trying to align the chip as well as
possible
with the pads. You go to the opposite corner and do another. If necessary,
you may have to walk the chip slightly into better alignment. When you have
all the pins reasonably well aligned, you just wipe the soldering tip
along the
rows of pins, and the solder will flow into the joints. If you use too much
solder, you will get bridges. These are removed with solder wick. When you
get it all soldered, apply rubbing alcohol to the chip and surrounding
area, then
scrub very gently around the leads with a sift bristle toothbrush for a few
seconds. Wash in water, then hit it with the blast from the kitchen spray
nozzle. I then violently shake the board to drive off excess water.

The soldering iron should have temperature control, and a very small
pointed tip.
I use either a Weller 1302 (old one) or the WSL with WMP iron (current
model).

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.


Ahh, it is VERY difficult to REMOVE such chips with simple irons, etc.

It can be done, but is very time consuming. On the other hand, the $40
package-specific desoldering heads can be adapted to some standard irons
to get a specific chip off cleanly.

If you don't want to save the chip, but the board, you can cut the leads
off with an x-acto
knife, use tweezers to remove the leads, then desoldering braid to clean
up. You can also
use braid to remove the solder, then lift each lead one at a time, but
that is really slow.

Jon

 

[Jon Elson]

Markus Zingg wrote:

Your advice is perfectly ok, let me tell you though, that I'm
regularly fabricating my own four layer PCB's at home.

Hey, I'd really like to hear about your multilayer process! I have the gear

for 2-layer, but often just have them done by commercial shops. But, I
could be real interested in any innnovative laminating and plating processes
you use!

Jon

 

[Markus Zingg]

Hey, I'd really like to hear about your multilayer process! I have the gear
for 2-layer, but often just have them done by commercial shops. But, I
could be real interested in any innnovative laminating and plating processes
you use!

Jon

Hi Jon

I recommend you then to join the

http://groups.yahoo.com/group/Homebrew_PCBs

group. There I posted the steps involved some weeks ago (search the
archives). Besides, the group is really a very good place to start.

If you have a trhough plating station (that's what I asume you mean
with "I have the gear for 2-layer") then you are basically all set. If
you don't have a trhough plating station then you definately will need
one.

Markus

 

[Brad Eckert]

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 assume you mean 208 pin and 240 pin QFPs. Use lots of flux and have

some solder wick on hand. I don't use a needle tip, the 1/16" tip
works just fine. The pins/pads pull solder off the tip and I add
solder to the tip (not the pins) as I go along.

The trick is to touch one pad at once so as to avoid bridging. With
some practice, you'll see which way surface tension wants to pull the
solder and how to get the solder to flow onto the pins. The sizzling
of the flux helps solder flow and gives you audible feedback.

 

[Leon Heller]

Brad Eckert wrote:

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 assume you mean 208 pin and 240 pin QFPs. Use lots of flux and have
some solder wick on hand. I don't use a needle tip, the 1/16" tip
works just fine. The pins/pads pull solder off the tip and I add
solder to the tip (not the pins) as I go along.

The trick is to touch one pad at once so as to avoid bridging. With
some practice, you'll see which way surface tension wants to pull the
solder and how to get the solder to flow onto the pins. The sizzling
of the flux helps solder flow and gives you audible feedback.

I've just treated myself to a used Metcal SSTS soldering station with a
selection of new tips. The 'mini hoof' tip I got is designed for drag
soldering and works very well on 0.5 mm spacing leads. With care (it
takes a bit of practice) there are very few solder bridges and the
joints need little or no resoldering. Metcal has some useful application
notes on soldering and desoldering techniques for different packages.

I'm now looking for an affordable stereo microscope.

Leon
--
Leon Heller, G1HSM
Email: aqzf13@dsl.pipex.com
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html