Motherboard soldering - Page 1
Forum section: electronics / beginners

author: iceisfun
author_rank: Regular Contributor
timestamp: January 22, 2014, 10:14:05 pm
content: I have a board with some bad caps and have had quite a bit of trouble heating all the way through. Are these things usually so stubborn?Got them out but can't seem to wick the solder out of the holes nor melt through and push new caps in

author: Nerull
author_rank: Frequent Contributor
timestamp: January 22, 2014, 10:16:13 pm
content: Motherboards are often multilayer boards with huge ground and power planes that can soak up a lot of heat

author: dfmischler
author_rank: Frequent Contributor
timestamp: January 22, 2014, 10:20:11 pm
content: The component lead sometimes makes it easier to heat up the whole mess (4+ layers, big ground and power planes, via). What are you using for a soldering iron and tip? I mainly use a Hakko FX-888D with a 3.2 mm chisel tip for this job.It might work to add solder to the hole and suck it all out with a Soldapullt. Or poke it out with a stainless steel needle or dental pick.

author: iceisfun
author_rank: Regular Contributor
timestamp: January 22, 2014, 10:23:42 pm
content: I have a Hakko 888 too with the default chisel tip it came with

author: IanB
author_rank: Super Contributor
timestamp: January 22, 2014, 10:28:04 pm
content: The default chisel tip is very small. You might try a bigger tip--it will provide a thicker heat conduction path.

author: mariush
author_rank: Super Contributor
timestamp: January 22, 2014, 10:58:01 pm
content: There are two alternative solutions.Don't bother whicking the solder.1. Add lots of 60/40 solder on both leads of the capacitor on the back side. Put solder iron on both blobs of solder at same time until solder is liquid and pull capacitor out.Put new capacitor leads on the holes, warm up the solder on other side and slowly push the leads in. The blob of solder will get stuck to the lead and move away from the board and now you can put fresh solder at the base of the leads.With this method, there's a small risk that when pulling out the capacitor some solder will get into the through hole and will make it harder to insert the new capacitors.2. So here's the twist to this method. Get some pliers, grab the capacitor and gently twist it back and forth to weaken the leads, after about 20-30 small rotations/twists the leads will break and there's going to be a few mm of leads on the top side.Now you can grab some tweezers, catch the lead in them, add a bit of 60/40 on the bottom, heat up the solder and use the tweezers to push the lead through the hole to the other side. Repeat for the other lead.I did the first method a lot and in 10-20% of the cases I ended up having to use fine stainless steel to clear the hole for the leads (you can find sets of such needles on eBay quite cheaply, they look like they're home made but they work).With the second method, it worked fine almost every time.. usually the lead breaks close to the capacitor leaving quite a lot of wire on the top for you to grab and push through once the solder is hot. And since the capacitor is no longer there to absorb heat, it takes less time to heat the bottom of the pcb and the solder, you notice quite fast that the lead is slightly moving around and you just have to push it through.In very few cases, the lead breaks flat by the pcb so it's harder to push it, but it's really not a problem if you have some stainless steel (or something that doesn't stick solder to) to push the remainder of the lead in either direction and clear the hole.edit: and btw, I'm using an old Hakko 936 with the standard conical tip, set at around 400-420c for motherboards (because the ground plane absorbs heat fast)

author: Psi
author_rank: Super Contributor
timestamp: January 22, 2014, 11:36:52 pm
content: Set the iron to 450C and place the tip across ways, so both component legs are touching the tip.Now flood it with a large amount of solder (so the iron tip and both legs are now one big blob) the component will usually come out after 5 sec or so.Or you will be able to wiggle it out.When trying to clear the holes of solder (so you can put in a new component) you will find that one of the holes is almost impossible to clear while the other is pretty easy.That's ok, with only one hole clear you can work on heating just the other hole while pushing in the component.

author: G7PSK
author_rank: Super Contributor
timestamp: January 23, 2014, 09:47:43 am
content: When changing caps on motherboards I just cut the old cap just above the seal with cable shears then pul the remains off the leads. This leaves the leads in the holes I then unsolder each lead but there is always some solder left in one or more holes. I found the best way to clear this is with a drill bit that is slightly smaller than the lead dia.I twist this in by hand holding the drill bit in a pin vice, solder being softer than the copper the drill will follow the solder I then use the drill lands to cut the solder back until the leads will push through the hole.Tin the leads put plenty of flux on them and the holes and re solder, job's done.

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 24, 2014, 05:45:09 am
content: I just use the good Ol' firestick type soldering iron with a fat chisel tip (big enough to go across both pins) for this kind of thing, being non-temperature regulated means it can build up a bit more thermal inertia, and because it is much quicker at desoldering, you don't heat up the surrounding area as much. - Just let it heat up until you think it is ridiculous, put some fresh solder on the tip, grab the cap with some pliers, touch the soldering iron to the pins and GENTLY pull.To clear the holes, people always suggest sucking, sucking sucking sucking. The problem with is that it is harder to get the airflow and pressure from sucking as you would from blowing. How do you fix that? Easy, just blow. Melt the solder with your firestick on the back of the board, whilst holding the nozzle from your compressor close to the front of the board, quickly remove the iron from the rear of the board and give a quick pull of the trigger on your nozzle. If you do this, be careful about the flying solder, it won't burn you, because it will cool rapidly as it goes through the air, but it may land in your eyes ect.