HP Forum Archive 19

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Surface soldered chips (HP71B) Message #1 Posted by Alberto Fenini on 22 Nov 2010, 11:03 a.m. Dear all, I need to desolder a couple of surface mounted chips from an HP71B board (actually the display drivers) since I would like to swap these with those from another unit. Does anybody has ever done something like this without burning the board itself ?? Thanks for help, Alberto

Re: Surface soldered chips (HP71B) Message #2 Posted by Alejandro Paz (Germany) on 22 Nov 2010, 12:02 p.m., in response to message #1 by Alberto Fenini There are several methods depending on the tools you have, the people you know and the utility of the chips you are about to desolder. This info is provided "as-is" without any explicit or implicit warranty or fitness, use at your own risk :). To not burn the board and other components you need to have some experience or know someone who does :), read below, please. If you are comfortable using a soldering iron and/or a hot air desoldering station, then it may be for you. If you don't, there are people who may help, maybe a cell-phone repair shop or similar. Someone you know may be of help. If you _do not_ need the chips you are about to desolder, the easiest is to cut (with a sharp-blade knife like a swiss-army one) the leads and then with the soldering iron and small pliers you remove the leads carefully. If you have the equipement but you are unsure, there are videos in youtube on how to rework with SMD parts, watch them and then practice with an old motherboard and so on before you touch the 71B. Have fun, Ale

Re: Surface soldered chips (HP71B) Message #3 Posted by Alberto Fenini on 22 Nov 2010, 2:49 p.m., in response to message #2 by Alejandro Paz (Germany) Thank you very much Alejandro, first of all I do need the chips, I want to try some swaps, but I do not know if that is the problem, so I may need to resolder everything. I have a traditional desoldering station, for old chips, and I did some tests, but without results. I do have a bosch air gun, with selectable temp, and from what I have read around, 270 ° C should do the work. I'll do some tests and will return to the fourm if anybody has done it before, I will appreciate any suggestion thanks again Alberto

Re: Surface soldered chips (HP71B) Message #4 Posted by Garth Wilson on 22 Nov 2010, 2:51 p.m., in response to message #1 by Alberto Fenini Use Chip Quik http://www.chipquikinc.com/index.htm They have a video demo on their website too. Chip Quik dramatically reduces the melting temperature of the solder so it stays liquid long enough to get all the way around the IC with the soldering iron and remove the IC before any of that solder hardens again.

Re: Surface soldered chips (HP71B) Message #5 Posted by Bill (Smithville, NJ) on 22 Nov 2010, 5:40 p.m., in response to message #4 by Garth Wilson As a Amateur Radio person, I've been following the SDR (Software Defined Radio) kits which ave surface mounted devices. There's a lot of articles and videos where Ham's have used fairly standard tools for putting their kits together. There are a lot of videos on You Tube which show some of these techniques. While I do have an SDR kit, I haven't yet tried to assemble it - probaby will be a winter project. Not sure if these soldering techniques will work with what you have planned for the 71B, but might be worth a look. Good Luck. Bill

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