High density connector troubleshooting

[mtwieg]

I'm working on a produce with a backplane and a daughtercard which connect with a very high density connector similar to this one. We apparently have some alignment issues, as we often get bent/broken pins if we are not very careful when mating the daughter card. But we cannot determine what the alignment error is.

I'm wondering if someone knows a trick for determining what parts of the connectors make contact first when mating. In the past I've seen mechanical engineers check for contact/interference with special paper which leaves visible markings where contact occurs, sort of how dentists use articulating paper to check where teeth contact each other. But I don't know what this stuff was called, and I'm not sure it would be suitable for this purpose (I don't want to ruin the connector, I'm hoping whatever this stuff is can be cleaned).

Anybody know what I'm referring to?

[mendip_discovery]

Markerpen? Paint it on, offer it up and see which gets marked. Then clean with IPA afterwards.

[DiodeDipShit]

Carbon paper comes to mind :  Black should show up on the gold terminals clearly. You may even find that You don't have to clean the terminals after, per this article:
https://www.frontiersin.org/articles/10.3389/fmats.2020.00219/full
Another thought is these terminals should have alignment pins, are they an option from Samtec Inc. ?

[mtwieg]

Markerpen? Paint it on, offer it up and see which gets marked. Then clean with IPA afterwards.

Something that could be applied with a marker or brush would be great for odd surfaces like this. But could you be more specific? "Markerpen" doesn't really help. Do you mean something like a paint marker?

Carbon paper comes to mind :  Black should show up on the gold terminals clearly. You may even find that You don't have to clean the terminals after, per this article:
https://www.frontiersin.org/articles/10.3389/fmats.2020.00219/full

Carbon paper might be the stuff I was trying to remember. Strangely I can't find any reference to it being a tool for mechanical engineering (seems to be marketed more as an art supply), but whatever, I'll order some and give it a shot, thanks.

Another thought is these terminals should have alignment pins, are they an option from Samtec Inc. ?

They do have alignment pins, either small ones integrated into the connector body, or larger ones as separate board-mount components. We've tried both, but the problem persists. It's clear that alignment pins aren't sufficient for full alignment.

[mzzj]

Engineers blue? Aka Dykem hispot?
Then there is also pressure sensitive color films like https://www.sensorprod.com/index.php

[DenzilPenberthy]

Engineers' Blue.  https://www.cousinsuk.com/product/engineers-blue-marking

Available as paste but you probably want the thin dissolved-in-solvent type. Search for layout fluid
e.g. https://www.talbot-tool.co.uk/Products/engineers-layoutmarking-fluids

It leaves a super thin layer which makes layout with scribe lines etc much easier and more precise, and will show up witness marks where surfaces contact. e.g. setting up gearboxes to get the teeth meshing correctly.


The low-tech modern version of this is to just use a Sharpie to draw on a surface. You might have an easier time marking up connector pins with some engineers blue in a spray can though.

[DiodeDipShit]

Anything is a tool for Mechanical engineering. We have used wood for quick prototypes, stickgum and cigarette wrappers for insulators and shims, Silly Putty for shaping and molding, I bought some of my best tiny tools at Sewing Machine stores, Art supply stores and Fabric stores. You can even get a fair, inexpensive little CNC machine for quick and accurate R&D of insulators, shims or gaskets from Cricut. Look at the Marker 3.
Carbon paper and Dykem are common to analyze and refine interfering fit. Dykem comes in spray cans, Liquid with a brush in the lid markers and they have a spray removal solution. It sprays very thin if used properly.
This may be Your best bet to find out if the connectors are being poorly aligned, have too much pressure at specific points between the male and female connectors meaning the issue may be in manufacturing and not Your fault.
I suggested alignment pins for the opposite side of the connector and receiving holes would have to be drilled into the mating connector. These would have to be done by a very reliable machine shop.
In regards to; the existing pins may be to small allowing useless 'precision' due to the mating part rocking. Try a couple of descending thickness split shims to connect the terminals in stages, this will reduce some of the rocking. You may also try using an fixtured arbor press to provide an even insertion.

[DiodeDipShit]

Correction to above: Liquid with a brush in the lid AND markers and they have a spray removal solution.

[mtwieg]

Thanks for the tips, I think engineer's blue/Dykem hispot might be exactly what I need!

I had tried articulating paper, but it didn't show anything useful, as it would only transfer on broader, flatter surfaces. I need to see contact on the actual contacts, which the paper will not conform to.

Could someone recommend a remover for engineer's blue which is electronics-friendly?

[DiodeDipShit]

Dykem may be the original 'engineer blue'. I've used for to many years to count......Dykem Blue can be used for 'hand drawn' circuit board board R&D. After the board is etched, Dykem Remover takes the blue off and the board is ready for components and  solder. Both the blue and remover are safe for circuit boards. I am not sure what would happen if You soaked a populated board in remover overnight, but it does evaporate quite quickly.

Dykem best for determinimg interference between parts, it adheres well, is aplication is very thin doesn't and it doesn't flake.
It also scribes well for layout.

You can buy Dykem many places, this one is a fair price:
https://www.emisupply.com/industrial-marking-products/paint-marker-cleaners/?q=dykem
MSD report:
https://assets.alliedelec.com/v1602583361/Datasheets/f10d95048d4ce8efd480dd19c5324f52.pdf

Soak a few components for a while to see if it renders them inoperative...... I bet they will be Okay in the end.

[mtwieg]

I looked around our machine shop last night and actually found a tube of Dykem hispot blue. But after seeing it up close, I'm very hesitant to try using it on these connectors/boards (they're effectively irreplaceable for the time being). Wasn't aware that it's oil-based, and it gets everywhere. Just loosening the cap a bit was enough to stain my hands. I'm worried that it (or whatever chemicals I'd have to use to clean it) will affect the plastic body of these connectors. I'll likely need to repeat this several times, removing all of it every time. After searching online I can't find any references to people using this stuff on plastic parts or surfaces.

Going to look around and see if we have any old rev board assemblies or connectors I can test on.

During my searching I also came across an alternative called "Canode" which is supposedly easier to clean, but apparently it hasn't been available for a couple years...

I'm thinking I should just try really simple things like magic markers/paint markers first. Maybe an art supply store would know a more suitable option too...

[Doctorandus_P]

The samtec connector shown has built in alignment notches. That means it should probably be the only thing attempting to align the connector halves. Any other guide (such as maybe a slot though wich the daughter cards move) should have plenty of slop so they do not interfere. I guess that >1mm should be the goal.

Maybe you can use some pieces of blue tac, then put some starch or other powder on the outside so it does not stick to anything else, then do a mating cycle and measure the thickness of the left overs.

[DiodeDipShit]

That Dykem hispot blue in a tube is greasy stuff. It is strictly machine shop stuff. It allows lubrication for sliding heavy parts when flat sanding for high spot removal.

Do Practice the mentioned Dykem Spray and the spray remover on a suspect connector. The spray lays down controllable thin layer or layers when You pass by quickly. The Spray remover quickly 'washes' the Dykem off in a rain.

Dykem Layout Fluid,Blue,16 oz,Aerosol Can:
https://www.shars.com/dykem-80000-blue-layout-fluid-16-ounce-aerosol-can     ..... $16

Dykem 82038 Layout Fluid Remover & Prep, 16 oz Aerosol
https://www.emisupply.com/itw-82038-dykem-82038-layout-fluid-remover-prep-16-oz-aerosol     ..... $15

For a mere ~$31 +shipping investment, You can't go wrong.