Date: 19970707 From: P. Faasse To: Multiple recipients of list CHIPDIR-L Subject: RE: paintstripper original mail from me: > >The source of my chips is a number of defect hard-disks; The > >components (52 pins PLCC) have been removed from the disk > >electronics by means of a paint stripper. I've got five of them > >by now and start to wonder what they do... reply from Mike: > I didn't know paint stripper could remove chips as well as desoldering, > nor have I heard that slang in place of desoldering before either. > Is there a special type of paint stripper or were you joking, if so > was the defect hard disk a joke as well ? (Didn't see a ";)" ) > Rgds > Mike > Perth, Western Australia > -- > Author: Mike The paint stripper I use is a 'hot air gun' type used to burn away paint (from wood eg..). I surely do not mean this remark as a joke. I use a Bosch 'hot air gun' that can be set for 300 deg C or 500 deg C. As a rule I use the 500 deg C setting. For a DIL chip I heat the bottom (pins side) of the PCB till I can pull the chip of the PCD (by means of pliers). For surface-mounted components I burn away at it right from the top. This may sound like a very crude and destructive way to treat a PCB but the results are very good. If you do it well you can get a large (100 pin) flatpack off a PCB without damaging either. The trick is to plan where to start (usually at one edge of the PCB) and to heat the components as short as possible. I have no real statistics about the results. I do tend to throw away any components that look burned badly. I have not detected any real damage yet (I use the technique for more than 4 years now). One thing you can not get off a PCB is elco's (the traditional types that is). They tend to short-circuit. SMD resistors, capacitors, many-pins chips and even IC sockets and connectors can be handled fine. I actually started this burning of PCB's when I had to get some 68000 pin-grid chips (about 30 of them) from PCB's for a computer club. I have never heard of dropouts amongst them yet, and this is 4 years ago.. I use pliers to hold the components while I heat the solder. When it melts you can pull the components off. For PLCC's I use a set of pincers, for connectors my bare hands. After taking them of the PCB I put the components on a metal plate to cool down. Before, I used both a small burner (hobby-burner for solering water pipes and the like). This tended to put the PCB on fire. I stopped using this method after I got a visit from the local fire brigade. They thought, not without reason, that my house was on fire. Using a burner tends to produce an enormous amount of stinking black smoke that would really do your health no good. I do however recommend the 'hot air gun' technique for private use only, please do not hold me liable for you destroying your PCB's or IC's. If you have more questions, they are welcome... -- P.R. Faasse -- Author: "P. Faasse" Date: 19971219 From: Therese Bublitz To: Jaap van Ganswijk CC: SBBN Subject: Re: desoldering > To: SBBN > From: Jaap van Ganswijk > Subject: Re: desoldering > >i see you have some idea's on desoldering... i have many boards that i want to > >desolder fast.. any idea's? > > Use an industrial 'hair dryer' (fohn?) or a gas burner. > I don't know the exact English terms for them, but > the first one is the hand held thing that woman use > to dry their hair, but then the serious kind that you > better not use to dry your hair! > The second one is a tank of gas with a burner on > top to burn of old paint from wood etc. > > I have once used the gas flame from a kitchen stove > to desolder a print quite rapidly. Watch out, it will > smell terribly afterwards! > > However when you're planning on selling the chips > again it's better to consult a serious refurbishing > company, because buyers don't easily accept used > chips and generally want to make sure that they > were desoldered correctly and afterwards handled > correctly. There are also special firms that > recondition the chips again, which means bending > the pins in the correct shape, testing them and > perhaps coating the pins so they are more easily > soldered (?). > > Also make sure that the chips on the boards are > worth all the trouble. Some buyers may perhaps > prefer to buy the complete boards and desolder > the chips themselves. > > Let me know more details if you would like me > to check the prices etc. > > > Greetings, > Jaap Dear SBBN: Your message was forwarded to us by Jaap van Ganswijk. Sorry for the delay but we have been extremely busy with last minute orders and emergencies this past week. I have been thinking hard on how to respond to your desoldering question here. A lot depends on what you intend to dio with the chips after you desolder them. I have been a technician for companies such as General Electric Medical Division ( catscans and ultrasounds ), and AT&T. My partner is a EE with experience in QC, designing test systems for the automotive industry, and for such companies as Gulf & Western, and Eagle Signal, etc.. We have quite a bit of exoperience in desoldering between us. The above methods may work for the hobbyist trying to desolder nothing more than transistors or old logic TTL . But Sorry guys; I shiver when thinking of using these procedures on a CMOS gates or a processor. You apparently don't have a decent solder gun or wand, it may be well worth the small charge to get one. The problem is that the parts today are very sensitive to heat and static charge. If you use the above blow torch methods then at least put a screwdriver, metal sheet, or some such metal device on the surface of the chip to diffuse the heat away from the chip itself. If the chips are some value and you plan on selling or salvaging them for another project then I highly suggest sending them to one of many refurbishing houses. The use a wave solder machine and can do it all in a day or so. The cost is pennies a part, and they will even check lead integrity, and all the things Jaap mentions above. IF you are in the States , let me know and I will gladly give you some names of places that do this sort of thing. If you have as you say 'many boards', it again is worth the trivial charge to have it professionally done. Best of luck and let me know if we can be of any further assistance. Therese MidWest Components Po Box 699 Chelan WA 98816 USA 509-687-1043 voice 509-687-4029 fax