From: "bbagnall" Cc: "Bike Current" Subject: RE: Soldering to a DeWalt circuit board? Date: Sun, 14 Mar 1999 14:10:04 -0500 Message-ID: <003401be6e4e$449a4d20$9b2af2cf@bbagnall.aegpaint.com> Scott wondered > Thus I thought about soldering directly to the prongs to protect the > circuit board. Bad idea? > Nothing that comes to mind (electrically), except some possible problems getting the solder/wire to stick securely.. However, the circuit board isn't all that sensitive in the contact area. You don't need a temp. controlled iron to do this. 25W-35W irons with small tips would be best. You can damage the printed circuit by "mashing down" too hard or heating a very skinny circuit trace (like around an integrated circuit), but this is not the case where the contacts join the board. If you follow the re-flow technique below (omitting the comments for scraping the contacts), you should be able to easily connect to the board Here are some soldering tricks I know: Only use rosin core solder. You may use additional, non-acidic flux to help clean the contacts. Scrape the contacts with some fine sandpaper and/or steel wool. Then "tin" these contacts immediately by heating with your iron then touching the solder to the contact (not the iron). If the solder flows evenly and doesn't bubble up in a round blob, you are in good shape to continue. If not, reheat, wipe off the solder blob (sometimes easiest by heating and then sharply tapping the heated item against a hard object, like a piece of wood. The extra solder will fly off, so be sure you don't mind getting some solder on whatever you tap on. You may need to ask your mother if its OK ;-] ). Rescrape and re-solder until you get an nice, smoothly rounded (but not circularly bubbled) patch of solder on the contact. Similarly, pre-tin the ends of the wire, to the same length as the tinned contact. Join the two by reheating the contact and the wire simultaneously. It should not be necessary to add any more solder at this point. Remove the iron as soon as the solder flows on both contact and wire. Continue to hold the wire still until the solder "freezes". You may find a pair of locking forceps or needle nose pliers very helpful to hold the wire completely still at this point, as the heat will travel up the wire quickly. This process is known as re-flow soldering and if both sides are properly tinned, results in perfect joints, avoiding the dreaded, lumpy "cold" joint, a frequent problem for beginners adding too much solder to a joint too quickly and then too quickly removing the heat. The cold joint not only looks bad but is mechanically and electrically poor, often failing under conditions of vibration or simple flexing of the wire. Cold joints can frequently be repaired by simply reheating the joint until the solder reflows smoothly. Cold joints are also caused by either or both pieces being joined having a layer of oxidation. "Clean and bright" prior to soldering is key. You might also consider several methods of "strain-relief" for the wires: You'll appreciate it when someone knocks the battery off the countertop and it doesn't rip your new wiring job apart. Adhesive backed nylon squares that have recesses on the top side to capture the wires using wire ties. Radio Shack and others sell these. Drilling a couple of holes in the case and threading a wire tie through is another way. Enjoy your smart charger