Tips and Tricks for desoldering with vacuum pump - Page 1
Forum section: electronics / repair

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: February 24, 2015, 11:26:40 am
content: After messing a little bit, I have finally repaired my VP800 desoldering station,https://www.eevblog.com/forum/repair/need-help-for-fixing-a-weller-vp800-desoldering-station/and started to use it.It is perfect for boards when the holes are large enough to provide ample space forthe solder to flow ( and this was the case in Dave's reviewhttp://www.eevblog.com/2013/11/01/eevblog-542-zd985-desoldering-station/),but things get much more complicated with multilayer boards with holes that are barely the size of the pins.In this case, at least for my minimal experience, I found that there was a very narrow path betweendesoldering the chip and ruining the board by lifting the pads.I tried to add some flux which seem to help, but still there is some place for improvement.I would like to ask you all if you have special Tips or Tricks to share for improving thes desoldering technics,with the aim of repairing the item, so not to ruin the board ?If I just want to salvage components, I may just go back to the heat gun technique, heating on the back, whichis very crude but very effective.PS : I took the opportunity of upgrading to "regular contributor" to add an avatar to my profile. Hope you will like it.

author: BradC
author_rank: Super Contributor
timestamp: February 24, 2015, 12:43:08 pm
content: Do not touch the board with the desoldering tip *ever*. You need to be as close to the hole as you can without physically touching it. If you have enough vacuum and enough heat you will clear the hole nicely.I have an Aoyue 701a station. It was pretty average out of the box (actually it was terrible). After fitting it with proper Hakko tips, and re-building the pump to solve all the vacuum leaks it sucks like the proverbial $20 lady of the night..Do not rub the board with the tip as that leads to pulling pads. Flux is good, and extra solder is better for really stubborn pads. For boards with big planes (external or internal) some hot air pre-heat is the go. I have an Aoyue 968 hot air gun and a cheap laboratory retort stand to position it. That frees up both hands to manipulate the board and the gun.Keep on top of your maintenance. Tiny vacuum leaks have a massive impact on performance, and they compound very fast. Silicone grease and silicone sealant are your friends.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: February 24, 2015, 12:56:19 pm
content: Thanks Brad for these very wise tips.I retain in particular the use of silicon grease, as I was wondering about sealant forlimiting air losses.It may not always be easy not to touch the board, but I see the point as when you touch it, too much heat is transferredto the board.

author: JuKu
author_rank: Frequent Contributor
timestamp: February 25, 2015, 09:12:37 am
content: Quote from: JacquesBBB on February 24, 2015, 11:26:40 amActually, that only feels crude (and smells bad), it is a gentle method for components. For SMDs, keep tapping the board and the parts fall off as soon as solder melts, very little stress on the part. Through-hole parts come off as easily as they went in. Often you even avoid melting plastic parts of a connector.(I try to avoid re-using parts as much as I can, but sometimes I get impatient wanting to try out an in-house prototype.)

author: Adal
author_rank: Contributor
timestamp: March 02, 2015, 07:21:04 pm
content: I use this "tool"http://youtu.be/WMICWniNgmIWorks very well. You only need a old fly back transformer.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 02, 2015, 08:00:25 pm
content: On the same page I like this one,But here again, all the example are easy as they are done with boards that have large pads an large holes. The difficulty I have is for a large and thick multilayer board with very small pads and holes so the difficulty is to really melt the solder and to have it flow properly.