Xref: utzoo comp.unix.xenix:3916 comp.unix.microport:2050 Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!killer!vector!rpp386!jfh From: jfh@rpp386.Dallas.TX.US (John F. Haugh II) Newsgroups: comp.unix.xenix,comp.unix.microport Subject: Re: Serial Boards Summary: soldering hints ... Message-ID: <8611@rpp386.Dallas.TX.US> Date: 13 Nov 88 19:01:33 GMT References: <343@puck.UUCP> <2657@nuchat.UUCP> Reply-To: jfh@rpp386.Dallas.TX.US (John F. Haugh II) Organization: River Parishes Programming, Dallas TX Lines: 49 In article <2657@nuchat.UUCP> steve@nuchat.UUCP (Steve Nuchia) writes: >To safely replace the UART it needs to be socketed; I've got internal >modems that have surface mounted 8250s and I understand that the telebit >internal has an 8250 soldered down. Oh Well. Adding sockets to unsocketed boards is a snap if you know the right procedure. All of this should be performed with your body suitably grounded, and a fine pointed soldering iron. Start by cutting the leads off of the old chip with a pair of narrow tipped cutters. Take a low wattage iron, 15 or 20 watts is plenty, and tin the tip well. Grasp each piece of left over lead with a pair of needle nose pliers, hemostats work perfectly for this. Then, heat the solder side of the board with the iron. The lead should come free in a few seconds. The trick seems to be keeping the tip of the iron clean and well tinned. Remove all leads before beginning the next step. Prepare the board for the socket [ or a new chip ] by removing the solder from the holes. If you are fortunate enough to have a solder sucker, you will know how to do this already, otherwise, you can remove the solder by placing a piece of copper solder wick between the board and the iron, and then heating the wick. You need to use fresh spots on the wick after each hole. Avoid leaving the iron in one spot for too long to prevent ruining the board. With all of the holes cleared out, insert the socket or new chip [ I suggest replacing any soldered in chips with socketed chips ] into the holes. A trick I use is the bend over pin 1 and the pin diagonal to prevent the item from falling out. Using very fine gauge solder, solder each pin to the board. You want to use fine solder [ 24 gauge or smaller ] so you won't have to heat the solder for too long. Always proceed with this step SLOWLY, allowing several seconds between each joint to reduce the likelyhood of heat damage to the chip. Of course, if you are installing a socket this advice doesn't apply. Finally, if you just added a socket, insert the chip into the socket as you would have if the original chip weren't soldered in place originally. No big deal. Surface mounted goodies are a different story ;-( -- John F. Haugh II +----Make believe quote of the week---- VoiceNet: (214) 250-3311 Data: -6272 | Nancy Reagan on Artifical Trish: InterNet: jfh@rpp386.Dallas.TX.US | "Just say `No, Honey'" UucpNet : !killer!rpp386!jfh +--------------------------------------