Needing help trying to separate stacked PCB's - Page 1
Forum section: electronics / repair

author: Blacknd
author_rank: Newbie
timestamp: November 01, 2019, 07:11:18 pm
content: I'm trying to figure out how to separate 2 PCB's held together by solder less pins without destroying anything.I need to separate these to get to some bad solder joints. This is a $1000 part that I know I can fix, if only I can access the points.Are there special tools to pull these pins from the board? I'm assuming the pins are solid and are connected on each board. I've tried pulling them apart, but was afraid of breaking it. Thought of making a tool to try and pry them up, but again I'm afraid of destroying it.My last though was to just saw the header in half and solder a new one on when I put it back together. I don't want to do this, but I'm beginning to think I'll have to.Any advice would be greatly appreciated.On a side note. Why the heck would a car manufacturer build headlight relays into the computer.... Basically my headlights stay on all the time. I took off the casing to the body control module and hooked it back to the car. I can LIGHTLY squeeze the relays and everything works as it should.

author: KC0PPH
author_rank: Unknown
timestamp: November 01, 2019, 07:24:24 pm
content: Reflow oven will do it nicely.

author: wraper
author_rank: Unknown
timestamp: November 01, 2019, 07:25:13 pm
content: This is press fit connector. You could use something that pushes those parts away. For example, two flat pieces of metal with matching threaded holes in them and using screws for pushing them away from each other. Breaking that connector is not a big deal actually. You can throw it away and solder usual pin header connector instead.

author: ogden
author_rank: Super Contributor
timestamp: November 01, 2019, 07:45:20 pm
content: I think cutting pins is right way of "disassembly". Unlikely that those pins could be reused. Even it it seems so - don't. Introduce board-board connector.

author: Ian.M
author_rank: Super Contributor
timestamp: November 01, 2019, 08:00:40 pm
content: It looks like cropping off the ends of the pins would release most of the contact pressure and allow the connector to be removed from the PCB, possibly after squeezing each pin to loosen it. I wouldn't care to use brute force to lever or jack the conector to PCB joint apart, as I suspect that for reliability, its designed for enough contact pressure for the pin edges to dig in to the hole plating to form a gas-tight joint, and I'd be concerned about the risk of ripping out the hole plating + any pads on the underside of the board.

author: Gyro
author_rank: Super Contributor
timestamp: November 01, 2019, 08:10:28 pm
content: I wonder if you might be able to deform (squeeze) each pin with a pair of good quality pliers of blunt cutters in order to release the tension?If you could, then you could simply solder them when reassembling and still have the other end to play with if you need to take it apart again in the future. An attractive option if so.Maybe just cutting off the tip of each pin (which would probably halve the spring force) and then flattening the pins before reassembly and soldering would do it.Edit: Oops, similar idea to Ian.M

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: November 01, 2019, 09:02:08 pm
content: Isn't that pcb from a Ford?

author: Rerouter
author_rank: Super Contributor
timestamp: November 01, 2019, 09:05:29 pm
content: That line on the side of the black piece really looks like a seam, are you 100% certain its not a connector? I've not come across mnay auto assemblies like that as it would be a pain to reflow.

author: pbarton
author_rank: Frequent Contributor
timestamp: November 01, 2019, 10:15:13 pm
content: Try thishttps://www.ebay.co.uk/itm/253424555640

author: ogden
author_rank: Super Contributor
timestamp: November 01, 2019, 11:04:24 pm
content: Quote from: pbarton on November 01, 2019, 10:15:13 pmDont. Those pins have barbs. By using brute force you may damage PCB.Look carefully:

author: wraper
author_rank: Unknown
timestamp: November 01, 2019, 11:24:28 pm
content: Quote from: ogden on November 01, 2019, 11:04:24 pmLook carefully, they don't

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 02, 2019, 12:24:17 am
content: I definitely wouldn't give it hot air or oven treatment, the holes are solder plated, if it still resists once heated you end-up with press-fit and solder, worse than before.If a well spread leverage won't do the trick, I second (third) the idea of squeezing each tip to take some spring out of them before levering.How you reconnect after is another debate...

author: Blacknd
author_rank: Newbie
timestamp: November 02, 2019, 12:34:10 am
content: Quote from: GeorgeOfTheJungle on November 01, 2019, 09:02:08 pmFiat.

author: Blacknd
author_rank: Newbie
timestamp: November 02, 2019, 12:50:52 am
content: I appreciate all the help. I'm going to attempt to squeeze the pins and try to pry it apart again.I've been worried of damaging the pins and it never occured to me that I couldn't reuse them anyways.I started to put a hot air gun on it earlier this evening.I wrapped as much as I could with foil, but couldn't get myself to put too much heat to it.

author: wraper
author_rank: Unknown
timestamp: November 02, 2019, 03:26:59 am
content: Quote from: Blacknd on November 02, 2019, 12:50:52 amPlease don't. Heating press fit connector is not only non productive, it's counterproductive. When PCB is hot, copper adhesion to PCB is severely weakened. PCB material itself is weakened as well, so chance of damaging something is severely increased. And in no way it will help separating PCB from that connector. If you don't plan reusing connector, just squeeze the pins with pliers or side cutters as already said.QuoteYou actually can if removal done properly. It's not like they must lose their springiness which is what provides tight fit between contacts and PCB.

author: Blacknd
author_rank: Newbie
timestamp: November 02, 2019, 03:35:46 am
content: Quote from: wraper on November 02, 2019, 03:26:59 amI was not going to heat the connector to try and separate it. I was going to try to reflow the solder on the points I cant reach. I had everything covered in foil that I didn't want heated. I chickened out though and glad I did before I really jacked it up.Decided on cutting the pins, but I need to pick up some smaller cutters.I'm still worried cutting the pins isn't going to relieve much tension and it's still going to be a pain to separate. I guess we will see. I don't have many other options.

author: drussell
author_rank: Super Contributor
timestamp: November 02, 2019, 04:23:15 am
content: Quote from: Blacknd on November 02, 2019, 03:35:46 amYou CAN get that kind of springy pins to come out, it's just a little tricky to get them started when there are very many of them close together. I certainly wouldn't cut them, I've never had a problem with connections after just squeezing them fully back into the second PCB. You could try squeezing some a little with small needle noses and see if you can get that area to start to come up. Once you get them going it really isn't that difficult. Just start at whatever end you can flex the boards a bit at and use some kind of prying apparatus like a plastic rod to force that part of the PCBs apart. As soon as it moves a bit, move further along the connector and keep prying a little at a time, working back and forth a little at a time. After a few passes they get fairly loose and the two will just fully come apart.To re-connect, you just need nice strong force carefully applied back and forth along the pins, in between at board level as the springy pins start to stick back through the board.I can't seem to find one like that here right now or I would make a quick video to show how to do it, but I've done it many times on various different boards with no real issues other than it being annoying and taking a little time.

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 02, 2019, 08:12:04 am
content: If you decide to cut (not the option I would have followed either) make sure you can get a clean cut. Squashed end with sharp edges isn't going to help...

author: Blacknd
author_rank: Newbie
timestamp: November 02, 2019, 12:31:44 pm
content: Quote from: drussell on November 02, 2019, 04:23:15 amMan i really wish i could see a video. Though i totally understand what your explaining, maybe it would give me more confidence. I would much prefer to just squeeze the pins and separate, then resolder when i put it back together.Another thing that worries me about cutting the pins is that i'm going to lose structural integrity between the boards. I guess if it comes down to it, I can just replace the entire header

author: drussell
author_rank: Super Contributor
timestamp: November 02, 2019, 01:36:21 pm
content: Quote from: Blacknd on November 02, 2019, 12:31:44 pmIf I have time later this afternoon I'll see if I can dig up something around here to video it. I think I have some backplane-plugin cards for some telco equipment where the connectors on the boards all use those press-fit pins instead of being soldered. Those springy-pins are actually quite common.Can you not get any area of the pins to evenstartshoving back up through the board by just pushing on the bottom of the springy pins, trying to push them up through the board? Sometimes I can just push down against the workbench / table or something (maybe the end of a screwdriver handle?) and work across it from the bottom. Works well with connectors where you can't pry from the top in any way until you create some room between the PCB and the connector housing on the top side, so you HAVE to start by pushing the springy pins back UP through the board before you can even try wiggling and prying the connector from the top.I've been fighting a nasty cold and don't have much of a voice right now but I could probably squeak out enough of an explanation into a video and test the "picture is worth a thousand words" axiom if I can find a piece to demo it on.Also, you shouldn't have to solder them when you stick it back together. Those pins create a LOT of force outward on the PCB holes and even after being removed once or twice will still have plenty of pressure to make a good connection without soldering them. This makes it possible to get apart again later if necessary. If you solder the springy end and ever need to disconnect it again you will have to desolder the other regular PCB side as you will never get the solder out from the springy pin side. They're jammed in there WAY to tight. This is why you should NOT heat up the area to try to pull it apart. If there is any tiny bit of solder plating those holes, you will make your task MUCH more difficult by melting it onto the springy pins!That WOULD work, of course, on your board-to-board situation but will NOT work on connectors that are springy-pin-press-fit to a PCB since there is no "other" side to desolder.The only times I have ever seen bad connections on those springy-pin things it was from SEVERE corrosion, and they had never been removed before or anything. Your pictures look perfectly clean and in good shape. You just need to carefully pry the things apart and they'll just squeeze back together after your repairs.QuoteYou COULD do lots of things but you'll be creating a lot of unnecessary work for yourself.

author: Blacknd
author_rank: Newbie
timestamp: November 02, 2019, 01:54:06 pm
content: Quote from: drussell on November 02, 2019, 01:36:21 pmSo after looking at this thing more, I'm beginning to wonder if i should just remove this connector instead of trying to separate the boards.I think removing it would give me plenty of room to reach the solder points. The bad points are directly behind this connector on the bottom board.This connector also used the press in pins, but they are slightly larger and I also have more area to start prying against.