Keith W8GX asked: I have never used a solder sucker before. How is one used when a part is still on the board? And what is a good solder sucker to buy?
------------------------ I remove the part first. Parts are cheap. If in doubt, cut the leads! After all, the PCB with the rest of the parts is the most expensive part you have. To tell the truth, you don't always have to do that. Often you can save caps and resistors by very *gently* lifting up on one end at a time while touching the iron to the pad to melt the solder. I use a very thin small screwdriver or dental pick (see your dentist - he/she usually throws them out regularly) under the lead whose soldering pad I'm going to heat. Then lift gently when the solder melts. You can usually heat the pad and lift from the same side of the board. Again, use your iron on the safest side of the board. That process can be facilitated by removing most of the solder first. If you can safely approach the PCB from the component side with your iron, heat that pad from the component side while using the sucker on the other side where the tip will sit against the board over the pad. The idea is to force all the air pulled into the sucker to come through the solder pad. That will usually leave very little solder in the hole. Sometimes you'll find the lead is loose in the hole after doing that. At the very least, a little heat will release it completely. If the pad is full of solder while you remove the part, it might take going back and forth several times, side to side, but resistors and caps usually come out easily. The trick is to NOT apply significant pressure on the lead the until the solder is molten to avoid pulling the plated through hole out of the board. Also avoid "cooking" the pads. The pads slowly debond as long as heat is applied. It's not just how hot they get, it's also how long they've been hot that determines whether a pad will come loose. Once the part is out, then I clear the hole using the solder sucker as needed. There's a *world* of difference between the bulb-type suckers and the spring-loaded type. In my experience, the bulb suckers are an exercise in futility 99% of the time. My first choice is the spring loaded sucker for best performance per dollar spent. Of course, nothing is as nice as the heated desoldering tools like the Hakko. Elecraft recommends the SoldapulltR model DS017LS. It is good. I also have a Radio Shack sucker that I suspect was made by the same people. Works fine. On-line, one of my favorite tool vendors is Tequipment (www.tequipment.net) who carries the Palidin 1704 (http://www.tequipment.net/PaladinTools1704.html or http://tinyurl.com/z8elf for a short URL) that sells for about $20. I not connected with tequipment but have made several purchases from them and liked the service the provided (and questions answered by a simple phone call when I was trying to decide exactly what I wanted to order). If you've got a spare $100 you can consider the Hakko powered desoldering tool that Tequipment carries as well. I'd probably buy one except that I do some of the documentation for Elecraft. I am careful to live in the same world as our builders, using only those tools suggested to our builders so I know that when I say something will work if done a certain way it's based on my actual experience and not what I "hope" would work. The worst thing would be to have a fancy desoldering tool on the bench and not be able to use it in good conscience! At the risk of stating a PCB "heresy" is this: if you are desoldering and suddenly see the little round donut of a solder pad stuck to your iron, don't panic. The little donut on the side of the board without any connecting trace is the easiest to debond, and it usually does not affect the performance of the rig in any way. Just be sure you don't tear or break any traces leading to the pad. If that happens, it's a sure sign that you are heating the pad too much for too long, but losing a donut won't kill the rig. Just go ahead and put in the new part and solder. The solder will bond to the plating in the hole and on the other side of the board. I solder and desolder at 700F unless it's one of the rare occasions I use some braid (pad too close to an obstruction to get the sucker over it, for example). When using braid I bump up the iron temperature to 800 F because of the heat-sink properties of the braid, and I keep trimming off the used braid so I'm always working at the end to minimize the amount of braid the iron has to heat up. Also, make sure there's a little solder in the hole and the iron is slightly wet with solder so the heat will transfer quickly. The biggest issue I see with braid is that people don't have some solder to start the transfer process and they don't have the iron hot enough so they end up cooking the pad until everything debonds. In my book, braid is the hardest way to clear solder from pads without damaging them. It requires the most skill to use successfully. The ability to change the tip temperature with a simple twist of a knob on the front of the unit one of the features I like best about my Hakko 936 soldering station. I find that's very important when I do use braid. Finally, I mentioned using a vice. A lot of builders don't have them. Over the years I've done without one more often than I've had one handy. A good alternative is to use a few books or even bean-bags (just avoid ones covered with static-generating plastic). Prop up your PCB with them so it's stable and you can get to both sides easily with your hands supported by the bench or other books. A minute spent properly supporting your PCB and your hands to approach the board with everything under control can save you hours of frustration after damaging something because your hand wandered or the board moved at the wrong moment. And always arrange things so you can see what the soldering iron is touching clearly. If you get the solder sucker in the wrong spot, you won't hurt anything. But you want to know where that soldering iron hot tip or body is at all times when it's out of the holder! Hope that helps a bit. Like anything, taking one's time makes doing the work a lot more fun! None of are racing the clock trying to disassemble a timer fuse on a nuclear bomb to save the world, I hope! So the fun, and success, is in doing it right, not doing it fast. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
