From: "david garnett" Newsgroups: comp.arch.fpga Subject: Soldering and Unsoldering PQFP by hand ... Date: Sat, 24 Feb 2001 12:54:16 -0000 Organization: UUNET WorldCom server (post doesn't reflect views of UUNET WorldCom Lines: 67 Message-ID: <978b66$hl1$1@lure.pipex.net> Reply-To: "david garnett" NNTP-Posting-Host: userdr22.uk.uudial.com X-Trace: lure.pipex.net 983019526 18081 62.188.6.29 (24 Feb 2001 12:58:46 GMT) X-Complaints-To: abuse@uk.uu.net NNTP-Posting-Date: 24 Feb 2001 12:58:46 GMT X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.ifi.unizh.ch!news.imp.ch!join.news.pipex.net!pipex!tank.news.pipex.net!pipex!tube.news.pipex.net!pipex!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:4818 CPLD's and FPGA's are both a curse and a blessing for prototyping - gone are those happy days spent wire-wrapping zillions of TTL gates, but come are the problems soldering PQFP packages - eg a PQFP 208 has the pins at a pitch of 0.5mm. For those forced by circumstances to hand solder these objects, a couple of hints which may come in useful one day ... Soldering 0) Check which way round the package goes ... 1) Use solder paste, a very fine tip soldering iron and a microscope of some sort (stereo, 15x is good) 2) Put down a couple of blobs of solder paste for the opposite corners of the device - do not bother with paste on the rest of the connections, as you will only push it around as you seek the correct position ! 3) Normally solder paste is applied using a silk screen, or with a very expensive device that squeezes out just the wrong amount. However, I have discovered that the plastic syringes that it comes in are flexible, and it turns out that you can easily apply the correct amount by squeezing the body of the syringe and dabbing the nozzle ! 4) Start by tacking down two opposite corners of the beast only. This allows you to fine tune the position. 5) When the position is correct, Check which way round the package goes ... 6) Now solder the rest of the connections. Do this by squeezing a blob of solder paste between each pair of leads. As you heat each lead, it is fun to watch the solder paste melting and running into position. Let the soldering iron dwell on each joint for an additional second or two to make sure that the solder has run into position. 7) Clean off the flux and solder paste remains 8) Now check which way round the package is once more ... Do not be suprised if you find it has rotated 90 degrees, which leads onto the second topic ... Unsoldering a PQFP208 You should never find yourself in this position, but if you do ... 1) Use fine solder wick to remove as much solder as possible from the joints. In my experience this leaves the lead still attached to the pad. 2) Now use a very sharp scalpel blade to slide between the pad and lead - it is suprisingly easy to break the remaining solder joint without bending the lead much - and after 208 of them you will get quite good at it ! 3) The chip will now lift off, so you can clean up and resolder. Note that there is a fairly good chance that you will lift the odd pad or two which has no connections, but this usually doesn't matter. Which brings me to one of those rants - why do the people who design packages insist on making them symmetrical - perhaps they think that they are immune from Murphy's Law ? regards to all, dave - "Don't worry - I've read all about this sort of thing in books !" Dave Garnett Metapurple Limited ###### Message-ID: <3A97D85E.306937C@algor.co.uk> From: Rick Filipkiewicz X-Mailer: Mozilla 4.75 [en] (WinNT; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.arch.fpga Subject: Re: Soldering and Unsoldering PQFP by hand ... References: <978b66$hl1$1@lure.pipex.net> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Organization: Algorithmics Ltd. Cache-Post-Path: mudchute.algor.co.uk!root@oval.algor.co.uk X-Cache: nntpcache 2.4.0b2 (see http://www.nntpcache.org/) Lines: 35 Date: Sat, 24 Feb 2001 15:50:54 +0000 NNTP-Posting-Host: 62.254.210.251 X-Complaints-To: abuse@ntlworld.com X-Trace: news2-win.server.ntlworld.com 983029857 62.254.210.251 (Sat, 24 Feb 2001 15:50:57 GMT) NNTP-Posting-Date: Sat, 24 Feb 2001 15:50:57 GMT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.ifi.unizh.ch!news.imp.ch!psinet-eu-nl!newsfeeds.belnet.be!news.belnet.be!colt.net!newspeer.clara.net!news.clara.net!news5-gui.server.ntli.net!ntli.net!news2-win.server.ntlworld.com.POSTED!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:4817 david garnett wrote: > Unsoldering a PQFP208 > > 2) Now use a very sharp scalpel blade to slide between the pad and lead - it > is suprisingly easy to break the remaining solder joint without bending the > lead much - and after 208 of them you will get quite good at it ! > There is another way to use the scalpel: Get a *new* blade and run it repeatedly with not too heavy pressure along the top of the leads where they join the plastic. Eventually you will cut through them. When you have cut through all 4 sides lift the armless chip off. Its easy to remove the legs & then - very important - use solder wick to clean the pads. Turn the iron's temp setting down as far as possible for this to make sure you dont lose any pads. Of course this crude method assumes you have a spare chip lying around but you did buy one or 2 didn't you ? Best to try & get hold of the more expensive versions whose pin 1 marker is fixed. > Which brings me to one of those rants - why do the people who design > packages insist on making them symmetrical - perhaps they think that they > are immune from Murphy's Law ? Even the rectangular packages have at least one way of getting it wrong - usually enough. ###### From: John Larkin Newsgroups: comp.arch.fpga Subject: Re: Soldering and Unsoldering PQFP by hand ... Message-ID: References: <978b66$hl1$1@lure.pipex.net> X-Newsreader: Forte Agent 1.6/32.525 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 87 Date: Sat, 24 Feb 2001 12:11:50 -0800 NNTP-Posting-Host: 204.182.55.6 X-Complaints-To: news@rmi.net X-Trace: den-news1.rmi.net 983045458 204.182.55.6 (Sat, 24 Feb 2001 13:10:58 MST) NNTP-Posting-Date: Sat, 24 Feb 2001 13:10:58 MST Organization: RMI.NET Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.ifi.unizh.ch!news.imp.ch!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.cwix.com!natasha.rmi.net!den-news1.rmi.net!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:4823 On Sat, 24 Feb 2001 12:54:16 -0000, "david garnett" wrote: >CPLD's and FPGA's are both a curse and a blessing for prototyping - gone are >those happy days spent wire-wrapping zillions of TTL gates, but come are the >problems soldering PQFP packages - eg a PQFP 208 has the pins at a pitch of >0.5mm. For those forced by circumstances to hand solder these objects, a >couple of hints which may come in useful one day ... > >Soldering > >0) Check which way round the package goes ... > >1) Use solder paste, a very fine tip soldering iron and a microscope of some >sort (stereo, 15x is good) > >2) Put down a couple of blobs of solder paste for the opposite corners of >the device - do not bother with paste on the rest of the connections, as you >will only push it around as you seek the correct position ! > >3) Normally solder paste is applied using a silk screen, or with a very >expensive device that squeezes out just the wrong amount. However, I have >discovered that the plastic syringes that it comes in are flexible, and it >turns out that you can easily apply the correct amount by squeezing the body >of the syringe and dabbing the nozzle ! > >4) Start by tacking down two opposite corners of the beast only. This allows >you to fine tune the position. > >5) When the position is correct, Check which way round the package goes ... > >6) Now solder the rest of the connections. Do this by squeezing a blob of >solder paste between each pair of leads. As you heat each lead, it is fun to >watch the solder paste melting and running into position. Let the soldering >iron dwell on each joint for an additional second or two to make sure that >the solder has run into position. > >7) Clean off the flux and solder paste remains > >8) Now check which way round the package is once more ... Do not be suprised >if you find it has rotated 90 degrees, which leads onto the second topic ... > >Unsoldering a PQFP208 > >You should never find yourself in this position, but if you do ... > >1) Use fine solder wick to remove as much solder as possible from the >joints. In my experience this leaves the lead still attached to the pad. > >2) Now use a very sharp scalpel blade to slide between the pad and lead - it >is suprisingly easy to break the remaining solder joint without bending the >lead much - and after 208 of them you will get quite good at it ! > >3) The chip will now lift off, so you can clean up and resolder. Note that >there is a fairly good chance that you will lift the odd pad or two which >has no connections, but this usually doesn't matter. > >Which brings me to one of those rants - why do the people who design >packages insist on making them symmetrical - perhaps they think that they >are immune from Murphy's Law ? > >regards to all, > >dave >- >"Don't worry - I've read all about this sort of thing in books !" >Dave Garnett Metapurple Limited > > Dave, my production people tack down two corner pins, put liquid flux on the rest, and feed the solder from the iron tip onto the pins. They have a special tip that has a small solder-reservoir groove... they fill the groove and run the tip down a whole row of pins, and each pin seems to slurp its fair share. They prefer to *hand solder* the fine-pitch parts, even though we solder paste, pick-n-place, and reflow everything else. They use some sort of infrared thingie to desolder all the pins at once. Checking the orientation does seem like a good idea. John ###### Message-ID: <3A987D76.DFB7EDCA@sprintmail.com> From: Ed Ngai X-Mailer: Mozilla 4.6 [en] (Win98; I) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.arch.fpga Subject: Re: Soldering and Unsoldering PQFP by hand ... References: <978b66$hl1$1@lure.pipex.net> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 67 Date: Sun, 25 Feb 2001 03:36:03 GMT NNTP-Posting-Host: 168.191.244.16 X-Complaints-To: abuse@earthlink.net X-Trace: newsread1.prod.itd.earthlink.net 983072163 168.191.244.16 (Sat, 24 Feb 2001 19:36:03 PST) NNTP-Posting-Date: Sat, 24 Feb 2001 19:36:03 PST Organization: EarthLink Inc. -- http://www.EarthLink.net Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.ifi.unizh.ch!news.imp.ch!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!feed2.onemain.com!feed1.onemain.com!newsfeed2.earthlink.net!newsfeed.earthlink.net!newsmaster1.prod.itd.earthlink.net!newsread1.prod.itd.earthlink.net.POSTED!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:4841 Hi David , my 2 pennys. david garnett wrote: > CPLD's and FPGA's are both a curse and a blessing for prototyping ... > Soldering > 0) Check which way round the package goes ... > 1) Use solder paste, a very fine tip soldering iron and a microscope of some > sort (stereo, 15x is good) If your not use to solder paste, then your not going to like the results. You will always make solder balls and you "Must" vent away the fumes of solder paste. You can use a hot air tool, but you can always use a ESD safe soldering iron. > 2) Put down a couple of blobs of solder paste for the opposite corners of > the device If you hand soldering, I've found a safer way. Put liquid rosin flux on pads. Put the FPGA into place, Wait 20, 30 sec. Thr rosin flux will be getting sticky. Get all the pins aligned, use a zoom scope. Touch a pad for a sec. the rosin will get gummy. This sticky rosin will hold the pin in place, Go around the whole IC. When your sure the PQFP is aligned, then use 0.010 solder. ... snip ... > 6) Now solder the rest of the connections. Do this by squeezing a blob of > solder paste between each pair of leads. As you heat each lead, it is fun to > watch the solder paste melting and running into position. Let the soldering > iron dwell on each joint for an additional second or two to make sure that > the solder has run into position. > > 7) Clean off the flux and solder paste remains I like useing either iso-propyl or ethyl alcohol. ... snip ... > Unsoldering a PQFP208 > You should never find yourself in this position, but if you do ... Use a hot air tool if possible. If not then alot of rosin flux and the smallest solder wick , look at Chemtronics for the free Solder wick chart. The small wick will not take away all of the heat from the soldering iron, also causing as less thermal damage to the tiny pads. A Weller WTCP w/ a #7 tip works all the time. > 1) Use fine solder wick to remove as much solder as possible from the > joints. In my experience this leaves the lead still attached to the pad. > 2) Now use a very sharp scalpel blade to slide between the pad and lead ... snip ... ###### From: Fred.Chu@avnet.com ("Chu, Fred") Newsgroups: comp.arch.fpga Subject: Re: Soldering and Unsoldering PQFP by hand ... Date: 1 Mar 2001 16:54:49 +0100 Organization: Mailgate.ORG Server - http://www.Mailgate.ORG Lines: 7 Message-ID: <96A045420EADD411A7F40004ACA36C6B01960291@amer28.avnet.com> NNTP-Posting-Host: porter.avnet.com Mime-Version: 1.0 Content-Type: text/plain; X-Trace: news.mailgate.org 983462088 29470 12.9.139.170 (Thu, 1 Mar 2001 08:48:05 -0700 ) X-Complaints-To: porter.avnet.com@abuse.net abuse@mailgate.org NNTP-Posting-Date: 1 Mar 2001 15:54:49 GMT Mail-From: Fred.Chu@avnet.com from porter.avnet.com [12.9.139.170] X-URL: http://www.Mailgate.ORG Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.ifi.unizh.ch!news.imp.ch!fr.clara.net!heighliner.fr.clara.net!newsfeed.online.be!ams.uu.net!news.mailgate.org!porter.avnet.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:4955 After some practice with PQ208's, you will find that PQ240's can be tackled just as effectively too. Fred Chu -- Posted from porter.avnet.com [12.9.139.170] via Mailgate.ORG Server - http://www.Mailgate.ORG