Need some unsoldering advice - Page 1
Forum section: electronics / beginners

author: sapperlott
author_rank: Newbie
timestamp: February 23, 2013, 09:45:33 am
content: Hi!I bought one of the cheap and popular Morion MV89A OCXOs off eBay. Unfortunately, it came still attached to a chunk of PCB. I just tried unsoldering the sucker but didn't quite get there. I used my Weller soldering station so I guess that shouldn't be the problem.I did get most of the solder off by using a good ol' sucker but there's still enough in there to keep the OCXO firmly attached to the PCB. I also tried solder wick but that didn't do anything at all - maybe mine is rubbish.So - any tips how to get this thing off? My next idea would have been to heat the whole PCB with a hot air rework tool that I can access at my local hackerspace and try to lift off the PCB once all the solder has liquified. But if there's a gentler way using just a soldering iron I would be very interested in reading about itOh - I'm basically having the same problem trying to unsolder a canned tuner module from an old TV card. Most of the signal pins already wiggle freely but the GND pin and the joints where the can is soldered to the GND plane are giving me trouble. Any advice on how to get this done is also welcome.

author: JuKu
author_rank: Frequent Contributor
timestamp: February 23, 2013, 10:34:54 am
content: Put the PCB upside down to vice, apply heat gun from bottom, keep tapping gently until parts drop. If needed, pry gently with tweezers (use a protection glove, hot air is invisible but still burns). There is no more gentle way. A soldering iron puts far more stress on a part. Do not drop precision oscillators or crystals to a hard surface, though.

author: sapperlott
author_rank: Newbie
timestamp: February 23, 2013, 01:49:21 pm
content: Thanks for the reply. So at least it looks like I got the right ideaAny recommendations regarding air temperature?

author: UPI
author_rank: Regular Contributor
timestamp: February 23, 2013, 02:44:26 pm
content: Have you tried adding fresh solder to the stuck joints and then sucking or wicking it out? That helps the heat conduct better through the entire joint allowing you to melt the old solder better. Also, preheating the entire area with hot air helps too.

author: cwalex
author_rank: Frequent Contributor
timestamp: February 24, 2013, 04:01:57 am
content: adding some flux as well can help on stubborn things but I think the hot air will be the best approach.

author: sapperlott
author_rank: Newbie
timestamp: February 24, 2013, 02:16:19 pm
content: @UPI:Yes - I added fresh lead-based solder (the original joints used lead-free solder). Didn't really help - I'm able to suck off most of the molten solder but the remaining residue is enough to firmly hold the part in place. One reason for this might be that it's a tight fit - there's not much space between the pin and the wall of the hole. I also thought about pre-heating but if I need to whip out the heat gun anyway I could just as well use the vice approach.@cwalex:Yeah - I also played around with my flux pen but no cigar. Looks like I'll go with the hot air + vice method.

author: PA4TIM
author_rank: Super Contributor
timestamp: February 24, 2013, 10:22:31 pm
content: Is it not glued to the pcb too ? I use a pace desolder station that gets allmost everything unsoldered but multylayer pcb with vias and connected to a groundplane are a pain.

author: Matje
author_rank: Regular Contributor
timestamp: February 24, 2013, 11:44:28 pm
content: Quote from: sapperlott on February 23, 2013, 09:45:33 amAhh, the MV89A, cool devices for the price.Ideally you would use one of these heated desolder devices with a tip with a hole going through it and a pump attached (de-soldering irons?), they work quite well, maybe your hackerspace has one. Big ground planes and stuff could still be a problem.For a MV89A using hot air should work, these take quite a bit of abuse. I have actually opened one with a propane torch to replace a broken capacitor, still works after soldering it shut again. Not so good for drift specs I guess though.The pins on these are quite rugged, you might get away with heating a pin, pulling it out a bit (in effect bending the PCB a little bit), letting it cool, doing the next pin, and so on. Would take a while I guess.

author: Smokey
author_rank: Super Contributor
timestamp: February 25, 2013, 01:28:05 am
content: Check out this post, and thread. Assuming the OCXO isn't actually glued down, it's probably the same issue.https://www.eevblog.com/forum/beginners/desoldering-tips-for-through-hole-components/msg158463/#msg158463If you wait long enough with a hot iron on the joint, any soldering iron capable of melting solder will heat the board up enough to remove the part. The key is waiting long enough, and it's always WAY longer than you think. Like minutes.

author: ddavidebor
author_rank: Super Contributor
timestamp: February 25, 2013, 06:16:35 am
content: Never more than 350c or you will detach the traces from the board

author: sapperlott
author_rank: Newbie
timestamp: March 16, 2013, 04:49:20 pm
content: Just went ahead and tried the hot air gun method yesterday. Worked great for the OCXO. Didn't work that great for the TV tuner, though. The parts inside the can came off. Oh well - that one was just a few bucks so not really a problem.