This is just bad soldering due to the part moving not vibration damage, correct? - Page 1
Forum section: electronics / projects

author: Psi
author_rank: Super Contributor
timestamp: May 27, 2025, 04:07:26 am
content: These dry joints are on some returned boards. To me it looks like the part moved during soldering.Just want to confirm it's not vibration damage as the product does have some vibration (automotive).The part is a little 4pin 5V to 12V 1W DCDC brick module. It's located right on the edge of the PCB, in a corner, which I know is not ideal and will be fixed on next version.There are 3 more of exactly the same modules on the PCB in the center of the board and none of them have this issue.The board is held down by 4 screws, one at each corner, so it can't shake around.My theory is that perhaps it's related to handling when being soldered at fab.Since it's on the edge of the PCB it's more likely to be disturbed by handling after being soldered but before the solder is totally set.And since its a SIP its at risk of moving around.Also the board is 6 layer 3oz so I'm sure it takes a while to cool down after exiting reflow oven.Because of the flux, which I'm pretty sure was not from me, I think they were hand soldered by pcb fab, and since the part is right on the edge of the PCB it might get disturbed by the operators hands when moving/repositioning the board after soldering but when its still molten.ThanksPics of a few different boards.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: May 27, 2025, 04:46:07 am
content: Quote from: Psi on May 27, 2025, 04:07:26 amTo me it looks more like mechanical stress, especially as the more exposed one is the only failure spotDo these modules get a tough time?

author: moffy
author_rank: Super Contributor
timestamp: May 27, 2025, 04:54:18 am
content: It looks like a combination of bad soldering and vibration combined, some of the joints look like the solder didn't wet the pin properly, but there is what also looks like fatigue from movement.

author: Psi
author_rank: Super Contributor
timestamp: May 27, 2025, 05:12:08 am
content: Quote from: PCB.Wiz on May 27, 2025, 04:46:07 amOther than the movement/vibration from riding in a car, no, not really.To me it looks like any vibration/mechanical-stress occurred while the solder was still molten or in the plastic region.I find it hard to explain how vibration after the solder fully set could cause those sort of round shaped voids around the pins.The pins are pretty thin and bend easily (0.3 x 0.5mm).I'd more expect to get metal fatigue in the pin causing it to snap off. Rather than the force pushing solder out of the way to create an opening through the via.The part in question.https://www.belfuse.com/media/datasheets/products/power-supplies/PDSE1-S.pdf

author: moffy
author_rank: Super Contributor
timestamp: May 27, 2025, 05:21:30 am
content: The second joint from the right looks like a fatigue crack.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 27, 2025, 05:53:31 am
content: Looking at each pin in each picture, I see what looks like every possible soldering problem!Vibration or movement while the solder is cooling.Dirty or oxidized pins that the flux wasn't able to deal with or not enough flux.Impact or physical force after the solder solidified that resulted in broken joints.Pins that desoldered themselves due to internal heat. This usually takes months or years.Cold solder joints due to inadequate heat or soldering time.Were these new boards or have they been in service for a period of time?Are the modules glued in place with something like silicone or hot glue like you often see in power supplies?

author: coppercone2
author_rank: Super Contributor
timestamp: May 27, 2025, 05:58:39 am
content: is this thing water fall soldered? Or through hole reflow, or hand soldered, or what?I have a tough time with the plastic region theory, because solder's plastic region is really smallbecause if you say its hand soldered, I can't see this happening. I wanna see someone replicate this plastic solder thing while hand soldering with a regular iron set correctly on that kind of through hole part.That solder is solidified like immediately when you remove the iron. The plastic region on a eutectic solder point... I don't even know how its defined. I think I saw videos of a experiment that showed that this region is tighter then 0.01c (the limits of their measurement)To me this is only a issue with non eutectic solders on ridiclously heavy copper parts like filling in the well of a lug with solder and putting way too small a wire in it (i.e. 20 awg wire into 10awg banana connector). With a heavy wire most connectors basically instantly solidify too because it cools it.If this is a result of a operator then they must be doing something so incredibly wrong we can't even think of it.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: May 27, 2025, 06:21:17 am
content: Quote from: Psi on May 27, 2025, 05:12:08 amHow much vibration? Where is this mounted? Can it get knocked or whacked during install and handling?Quote from: Psi on May 27, 2025, 05:12:08 amOn a single wire, maaybbee... but on a 4 leaded part, it cannot really move when other pins are soldered.Movement during lead free solder usually has a more crystaline/powerded appearance.With parts like this, we usually specify they are held down during soldering, so they are hard down and square on the PCB on their flanges.Are these hand soldered and done last?

author: jonpaul
author_rank: Super Contributor
timestamp: May 27, 2025, 06:46:24 am
content: lousy tools and technique. Poor soldering temp, poor thermal transfer.Suggest a Metcal SmartHeat like my SP-200Jon

author: tooki
author_rank: Super Contributor
timestamp: May 27, 2025, 07:04:25 am
content: To me, looks like poor soldering followed by vibration damage. If I had to name a proximate cause, I’d say vibration. The poor soldering certainly doesn’t help, but I don’t think it’s to blame per se.Are the DC-DC modules flopping in the wind, or are they secured with silicone or something?

author: Psi
author_rank: Super Contributor
timestamp: May 27, 2025, 07:38:01 am
content: Quote from: tooki on May 27, 2025, 07:04:25 amThey usually don't flop in the wind. They are soldered flat on PCB and the plastic case keeps them flat. Then the board now get conformal coated which holds them down even more. (ones in photo are older without coating or with an older coating that was shit).Room for improvement here with some sort of a glue. I think it will have to be actual glue not silicone.Anyone got ideas what to use?Quote from: coppercone2 on May 27, 2025, 05:58:39 amI dont have transparency on exactly how PCBway soldered them. All the SMTs on both sides are reflowed normally in reflow conveyer.But for the TH stuff my best guess is placed by hand and then soldered by touching them with a solder pot or manual water fall system under the PCB.Since that would be fastest way than soldering each pin individually with an iron.Quote from: PCB.Wiz on May 27, 2025, 06:21:17 amYes, as I said they are on the edge of the PCB so being wacked during install and handling is a real concern.I'm fairly sure yes, all the TH stuff is done last.Quote from: edpalmer42 on May 27, 2025, 05:53:31 amService for a year or two.See above. Just soldered flat to PCB and then conformal coated.

author: coppercone2
author_rank: Super Contributor
timestamp: May 27, 2025, 07:56:14 am
content: I would imagine a hard core place like that has a robot soldering iron with a feeder for basic parts like that, their volume must be ludicrousif they have a bunch of little solder pots or something then maybe you can nudge it because they will totally pump a massive amount of heat into the PCB and it might stay liquid a little longer. but again, eutectic has basically no plastic region. It would look like crystals if it was disturbed while slow cooling. Like there would be some sharp edge protrusion

author: coppercone2
author_rank: Super Contributor
timestamp: May 27, 2025, 08:05:11 am
content: are you sure its not like a volcano shape, where the solder cracked and there is a cone shaped object (facing into the PCB with the sharp point) that is hammering up and down on the solder joint as the chip vibrates?like imagine you took a volcano, got a cone that fits in to it, put it on a rod, and moved it up and down so it keeps hammering the crater causing it to like raise up. they kind of look like volcanosor you could say it looks a little like bullet holes (which are formed by cone like objects deforming metal) or perhaps those holes in space craft from small meteorites. and then it cold flows and possibly re-binds itself into the hole because its mangled and 'sticky' at that point after it did some damagelike look at the picture here of how it cracked on a circle perimeterhttps://express-24.io/articles/cracked%20soldering%20joint%202.jpgif you keep 'banging' on that it might make the shape you have in your picture? kinda. the part that cracked off is too big to fit through the hole so it starts to broach/deform/whatever it when it shakesI think usually it cracks in a way that lets the pin 'slip out' easily so you don't see it. but if it cracks into a 'clog' it could start working on itI don't know why it would look like a "atoll" if you disturbed it while freezing. I think it would more look like its off to one side with some odd shape sticking out of it. Unless the pin vibrates like a tuning fork to displace things from the middle into atoll shape. but its too round IMO, if the pin was doing that it would be a oval that is thin on the edges. I know some pin shake, i.e. if you knock on a VFD (display) you can hear something working like a tuning fork inside for quite a while. but that is very stiff metal on glass with vacuum inside, this is some potted brick that is a damperdid you check if the part is seated correctly or if it moved up? I.e. the gap under the part. is it level too

author: Psi
author_rank: Super Contributor
timestamp: May 27, 2025, 09:31:00 am
content: Quote from: coppercone2 on May 27, 2025, 07:56:14 amFor large orders sure, but my orders are usually 100 or 150, so probably too small to bother setting up a TH robot.You could probably hand solder 1/2 of them in the time needed to setup the machineI'm just guessing though

author: coppercone2
author_rank: Super Contributor
timestamp: May 27, 2025, 09:44:31 am
content: i imagined its all setup to automatically do everything but maybe I am thinking too high tech

author: Psi
author_rank: Super Contributor
timestamp: May 27, 2025, 11:02:22 am
content: What sort of rigid glue is PCB safe.Looking for something to glue these DCDC modules down to the PCB in a way where rough handling is less likely to bend them over.Silicone wont hold them down if someone grabs the board with their thumb on the DCDC module.Is there 'PCB safe' 5min epoxy?Perhaps some sort of UV based glue?

author: tooki
author_rank: Super Contributor
timestamp: May 27, 2025, 06:03:58 pm
content: I would think that vibration would be the bigger issue, not manhandling?Silicone will dampen a lot. Especially a harder one. There are lots of polyurethane and epoxy potting compounds, some of which might work if allowed to thicken a bit before applying.And of course there’s always epoxy adhesive.

author: moffy
author_rank: Super Contributor
timestamp: May 27, 2025, 11:33:57 pm
content: In high vibration environments there is also the matter of the board flexing, not just securing the components to the board, how well it is affixed and how large and thick the PCB material is also matters.