Desoldering nightmare - Page 1
Forum section: electronics / beginners

author: s_lannan
author_rank: Contributor
timestamp: July 02, 2011, 03:49:42 am
content: I'm trying to desolder 16 pin dip chips off of double sided class D amplifier boards and am having a real pain getting them out.The only way I have gotten any out is to CUT the legs off the IC and get them out that way.I'm using a temperature controlled soldering iron and have tried solder suckers and solder braid.The more I try the worse the pads on the board get...Is there a tool I can buy to make this job much easier? It is doing my head in! Help!

author: gregariz
author_rank: Frequent Contributor
timestamp: July 02, 2011, 04:07:52 am
content: Sounds like no-lead solder? If it is I find feeding a lot of 60/40 solder into the joints until it flows easily into the wick/braid is what usually works for me.

author: s_lannan
author_rank: Contributor
timestamp: July 02, 2011, 04:38:05 am
content: yeah i did that it definitely improved matters but i can see the solder on the component side still bonding to the legs and pads+vias... Its very hard to do anything on the component side as the boards is highly populated with tall capacitors etcTo add my current idea of a solution for this kind of work is to get a desoldering gun with a vacuum like that pricey den-on sc7000.....

author: vtl
author_rank: Regular Contributor
timestamp: July 02, 2011, 05:39:19 am
content: I find those solder suckers only useful for sucking up the excessive blobs of solder. You usually still end up with enough solder on the joint so you'll have to finish it off with the braid.Soldering braid alone shouldve worked. What kind of braid are you using? Is it flux dipped? Smoke should come out of the wick when you heat it up. Even with flux dipped braid it might still be helpful to use extra flux on the pins to get it out. Theres no way you need specialized vaccumpump desoldering tools to desolder a simple dipchip.What kind of soldering tip are you using? You need a decently beefy tip because you have to heat up the wick placed on the joint you're trying to desolder. If youre using one of those fine tipped conical tips then you'd be sitting there for ages.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: July 02, 2011, 06:39:51 am
content: If you don't need to reuse the chips clip and rip is your best method. You used to be able to buy a desoldering 'shoe' that was like a large U shaped solder tip that heated all the pins at the same time. The main problem I have found with unsoldering Dip chips is that the legs are slightly splayed and remain in contact with the sides of the through hole, by the time you have gone around all the pins the first one has cooled and re bonded. You could try a heat gun and GENTLY heat the whole board around the area of the chip while prising the chip up on the other side with a screwdriver but generally they are a PITA .

author: dimlow
author_rank: Frequent Contributor
timestamp: July 02, 2011, 07:39:23 am
content: If this is an old board, and the solder is not flowing well, try some plumbers flux, its a lot more aggressive and you have to clean the board well after using it because it is corrosive if left on the board. I have used it with good results on some 30 year old boards. But remember to CLEAN THE BOARD AFTER.Did i say CLEAN THE BOARD AFTER USING IT ?? yea, i think i got the point over..

author: Bored@Work
author_rank: Super Contributor
timestamp: July 02, 2011, 07:51:56 am
content: Practice, or the lack of thereof.Practice on an old board you don't need. 16 pin DILs can well be done nicely with a mediocre iron, solder wick and a solder pump. An alternative would be hot air, but that isn't really needed. In the old times, those with limited practice or less time at their hand did use special DIL desoldering tips. You can still get them, but I haven't seen them used in ages and they are anyhow not really needed unless you need to do many DILs dailyhttp://weller.nl/advancedview.php?cid=401

author: vk6zgo
author_rank: Super Contributor
timestamp: July 02, 2011, 02:12:17 pm
content: Some boards have the pads for DIL ICs way too small.This gives a saving in copper,& maybe room for thin tracks between pads.They wave solder OK,but are nasty when you have to desolder them.I have found that the boards I have problems with are usually European ones,Japanese ones are usually OK.The Sony boards I used to work on were untidy looking,but worked for years,& when you did have to fix them, desoldering components was a simple matter.The Barco boards,on the other hand,looked beautiful,but were unreliable,& you could easily cook one or two undersized pads if you wereunlucky.VK6ZGO

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 02, 2011, 04:18:46 pm
content: For heavy boards the only reliable way to get the chip out without damaging chip or board is a heated vacuum desolder tool, and sometimes even even you need to use a second iron on the other side to get the heat in quickly enough to avoid PCB damage. The Metcal desolder tool is the best I know of for this, but needs a compressed air feed and Metcal PSU so an expensive option.If it's leadfree then flooding with leaded (preferably 2% silver) definitely helps.If you don't care about the chip then cutting the pins off is teh best way to reduce risk of PCB damage - note some IC pins are magnetic, so if you hold a magnet over the pin, it jumps out as soon as the solder has melted.

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2011, 04:44:16 pm
content: Ive had horrible experiences with some PCBs that have DIL lead holes that are barely a clearance fit. It is so easy to rip a copper feedthrough out. In such cases I have always ended up resorting to the 'cut, heat and pull' method for each pin as that seems far safer than any other method I have tried.I have used the Weller DIL desoldering blocks and whilst they are OK, they still prove difficult to use on PCBs and you really need the PCB vertical in a vice whilst using it.

author: sacherjj
author_rank: Frequent Contributor
timestamp: July 02, 2011, 06:56:33 pm
content: I've had luck using the 858D+ hot air iron to keep the solder melted while I gently pry on each side and ease the DIPs out. I also use a healthy application of flux (real soldering kind, not plumbers.)

author: s_lannan
author_rank: Contributor
timestamp: July 03, 2011, 02:42:21 am
content: Quote from: sacherjj on July 02, 2011, 06:56:33 pmI have considered this method, Is there a ballpark figure for temperature setting without damaging the board?

author: sacherjj
author_rank: Frequent Contributor
timestamp: July 03, 2011, 04:25:45 am
content: Quote from: s_lannan on July 03, 2011, 02:42:21 amI set it about 300C and just keep it moving.

author: _Sin
author_rank: Regular Contributor
timestamp: July 03, 2011, 10:23:05 am
content: I just did something very similar, removing 16-pin chips from an old board for a project I"m working on. In my case snipping the pins wasn't an option as I needed the chips and the board intact.The most effective technique I tried was to have the board clamped vertically, so that I could apply heat to the pin on the component side of the board while having the solder-sucker over the pin on the rear.All the chips came out cleanly without damage.