High density non-destructive connector desoldering suggestions - Page 1
Forum section: electronics / repair

author: HalFoster
author_rank: Frequent Contributor
timestamp: January 06, 2025, 04:43:35 pm
content: I am needing to remove and the replace the connector shown below on a few (~5) boards without damaging either the existing pads or the adjacent circuitry. It is a 6-8 layer board and fine pitch traces - standard de-soldering methods seem risky so I am hoping that someone here has experience with similar situations and can offer advice.Thank you!Hal

author: inse
author_rank: Super Contributor
timestamp: January 06, 2025, 06:24:42 pm
content: One safe method without special equipment would be to cut off every pin as far away from the pcb as possible.Apply flux on the solder joints, put the pcb vertical and remove pin by pin with soldering iron and tweezers.Then carefully clean each hole with desoldering gun or wick.Time consuming but safest method for the pcb.

author: tooki
author_rank: Super Contributor
timestamp: January 06, 2025, 06:28:32 pm
content: I would mill a copper block to have a small well for each pin, as well as bored holes for some heating elements. Fill each pin well with solder. This becomes a giant desoldering tip that melts every pin simultaneously. (I have such things for DIP ICs, and my old job had them for some larger connectors too.)Or use a solder bath.

author: tooki
author_rank: Super Contributor
timestamp: January 06, 2025, 06:31:19 pm
content: Quote from: inse on January 06, 2025, 06:24:42 pmThe desoldering blocks* (and similar methods like solder baths) are even gentler, since there’s no risk of mechanical shock damage from snipping pins.*”Entlötstempel”, they are called in German.

author: inse
author_rank: Super Contributor
timestamp: January 06, 2025, 06:36:10 pm
content: I agree, but my proposal included the phrase „no special equipment“.Mechanical shock can be avoided by dremeling off the pins with a small cutting disc.It may be challenging to apply the block evenly over all the pins taking into consideration the size of this connector.Still the task of cleaning every hole remains.Btw, what‘s the problem with the connector?I didn’t notice signs of wear and tear.

author: factory
author_rank: Super Contributor
timestamp: January 06, 2025, 07:36:38 pm
content: Quote from: inse on January 06, 2025, 06:36:10 pmMaybe that is a good board and the others have broken pins, this did happen with boards at work, though I think 64 pins was the most anything had.As the connectors we had were damaged, I would usually cut the pins & remove on by one, then add some fresh solder and desolder with a Pace desoldering iron.Removing connectors complete was possible with the Pace, then checking each pin was loose before removing, repeat adding fresh solder if they weren't loose. You do have to be careful, other people would get impatient & cause damage, desoldering tip needs to be in good condition too.Lining up the connector pins was fun too for those round pin connectors, especially if there wasn't the other half available to hold them.David

author: langwadt
author_rank: Super Contributor
timestamp: January 06, 2025, 07:41:46 pm
content: Quote from: tooki on January 06, 2025, 06:28:32 pmmight as well make it one big well and just stick it on a hotplate

author: amyk
author_rank: Super Contributor
timestamp: January 07, 2025, 03:17:44 am
content: I'd use a suction desoldering iron. Hakko FR-301 or equivalent.

author: tooki
author_rank: Super Contributor
timestamp: January 07, 2025, 01:51:36 pm
content: Quote from: langwadt on January 06, 2025, 07:41:46 pmI think that’s called a “solder bath”.

author: Swake
author_rank: Frequent Contributor
timestamp: January 08, 2025, 01:52:50 pm
content: Woow, this is a challenge !A solder bath sounds risky, would be realistic only if it is big enough and if solder contamination is no issue.I'd go pin by pin. To limit thermal problems maybe also ask for an experienced helping hand as that would accelerate things. One person heats the stuff, the other pulls it out (gently of course).Use liberal amounts of flux.Use copper or aluminium tape to protect surrounding components from heat and physical damage. Kapton tape is also an option but does not dissipate heat as fast.Hope you have a board to experiment with.@HalFostertake picture of your undertaking!! Or better a time lapse videoGood luck

author: langwadt
author_rank: Super Contributor
timestamp: January 08, 2025, 04:19:32 pm
content: https://youtu.be/DyNVgOVDarA?si=IDVx323nQzuXp28-&t=37

author: tooki
author_rank: Super Contributor
timestamp: January 08, 2025, 08:39:37 pm
content: Quote from: Swake on January 08, 2025, 01:52:50 pmWhy do you think that is risky? It is probably the lowest-risk method available.

author: inse
author_rank: Super Contributor
timestamp: January 08, 2025, 08:42:19 pm
content: I wonder whether HalFoster will show up again to the topic he started…

author: HalFoster
author_rank: Frequent Contributor
timestamp: January 09, 2025, 01:08:07 pm
content: Thanks all for all of the suggestions - sorry I'm just now answering but my wife was in an accident over the weekend (she is OK, car is not) and I have been dealing with that as well as a 94 year old mother with dementia that is having a bad week. So... priorities.First of all, I apologize for not making it clear that the desire was to save the connector as well, otherwise just cutting it out and removing the pins individually would work fine. These boards are part of a legacy MIL testing system and they as well as a majority of the components are not available any more - yet, of course, the Powers-that-Be in their infinite wisdom desire them to be repaired anyway. So, trying to find a way to accomplish this while still staying within requirements. The problem with the connectors is broken pins on the mating side. The ones towards the top of the connector can be replaced however there is really no way to get to the bottom ones with the connector in place. It is possible to remove the ones above to a point but the last two - especially the bottom most one - is impossible to reinsert with the connector in place. If it was a SMT connector that would be different, but it of course isn't...Really the only way I feel might work would be a solder bath limited to just the area with the connector pins - a machined reservoir thermally isolated from the rest of the board. It's a 180 fine pitch connector so there is also a major concern of getting it reinserted even if it could be removed and repaired. Anyway, it is not something that *has* to be made to work - it just would be a feather in the corporate (and personal) cap if we could.Thank you all again,Hal

author: JohanH
author_rank: Frequent Contributor
timestamp: January 09, 2025, 02:18:44 pm
content: So this method works fine with smaller connectors. Take a copper wire and lay it out between the pins and fill with lots of solder. Then apply heat with a soldering iron to the copper wire, and the connector just drops out when the solder melts. Now, with this connector, if it would work at all, it would require lots of solder and some more appropriate heating method.What if you used four separate copper wires (soldering them to the pins in the same way), connect the wires in parallel at both ends, then connect both ends to a beefy power supply with current limiting or at least with adjustable voltage. Then start increasing voltage/current until the solder melts. If necessary, monitor the temperature with a thermocouple. The problem only is that it might require a rather powerful power supply.

author: inse
author_rank: Super Contributor
timestamp: January 09, 2025, 02:54:33 pm
content: It’s about MIL technology, no need for homebrew solutions.I guess he could involve all kinds of special equipment.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 09, 2025, 03:07:56 pm
content: to save such a connector and minimize any damage is a solder bath flux on each side of the pcb and dip the connector, and it should pop outgoing one by one pin with a desolder pump is to risky while the pin is in therenobody talked about the thermal mass or even the grounding on this connector, board thickness combined will make things harderyou need to do it in one go in a solder bath and after you empty the holes,even seen guys using hot air until solder melt and push an jet or compressed air in the holes, the other side of the pcb had huge / wide kapton tape to protect against the compressed air effects

author: HalFoster
author_rank: Frequent Contributor
timestamp: January 09, 2025, 03:33:15 pm
content: @coromonadalix - That's pretty much what we are looking at now - mill a solder bath fixture to fit the outline for removal, hot air the holes and pray it will go back in. We have a couple parts boards with connectors close to the ones in question so will experiment a little. We finally found one board house that feels confident they can remove them at a fairly quick turnaround so at least "Plan B" is there if needed... but it would be nice to be able to manage it ourselves if possible (it's slow through the rest of the month so a challenge such as this is welcome.)Hal