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spring fit solderless iGBT? Skiip

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coppercone2:
So the IGBT in the machine I am servicing now appears to be a press fit assembly. Its held on through 2 screws into a nylon holder to press it into a PCB with pads that are covered in solder it looks like.

this IGBT blew up and looking at the mechanism its really weird.
https://www.semikron.com/innovation-technology/packaging-technology/press-fit-technology.html

Is this popular? is this good? Its filled with telephone company goo.

My IGBT is not the same as the article, it actually is a SMD device, it has pins much like the new multimeter 9V pins, that press into the exposed solder pad contacts (I think thats what they are). Yes, a big press fit SMD device, no plated through holes required.


 I noticed also, two of the many pads have arc damage, since I ordered a new IGBT, is there anything to watch out for in preparing this contact surface for a new IGBT module? I am kind of thinking arc damage at contacts is a bad sign for this technology...

I have this one specifically,
https://www.semikron.com/innovation-technology/packaging-technology/skiip-technology.html

Could this be the reason why the welder failed? Arcing contact maybe caused some problems.. I would say "well lets solder it on", but get this, its a 3 piece assembly,

so

the semiconductor is press fit into the spring, that press fits into a FR4 PCB board, and its all held together by two screws in the middle to make a sandwich. So if you even did solder it yourself some how, there is still ANOTHER mechanical connection inside the module, so the IGBT has TWO contacts per PIN. Its a 600V 6A unit.

My plan is to clean up the pads with alcohol and grease lightly and place in the new iGBT.

It happened to blow up right where the logo is, so I recommend putting two inscriptions on large power components, I had to put the pieces back together with tweezers like sherlock holmes to read the part # lol

Berni:
Press fit can actually be more reliable than soldering.

Most connectors in automotive are press fit due to thermal/shock/vibration resistance. A lot of very big >50A PCB mount terminals/connectors also use press fit. You also get copper to copper contact making for a lower resistance connection.

I suppose they can be more susceptible to corrosion due to the thin amount of material involved, but that might be about the only down side.

T3sl4co1l:
As with any other technology, it must be properly applied.  The first barrier to good press-fit THT connectors is getting precise, finished plated, hole I.D..  Usually the datasheet says something like +/- 0.001", whereas general fab is 3 to 5 thou.  Then they have to be assembled carefully, and probably the connector should be glued in so the pins aren't wiggling around under vibration.

They can be quite reliable, but they're also used at scale.  They're popular for mainframe backplanes in part because you don't have to try and solder anything into the 32+ layer, 1/4" thick board.  The leads don't even stick out the other side, there's nothing to solder to.  But these applications also use thousands of pins, and say they have a 99.9% success rate -- it might sound good individually, but in total, you have a very good chance that one or two pins haven't made it.  What then?

I'm not aware of any power devices with sprung surface contacts.  That sounds kinda dumb.

Tim

coppercone2:
well I don't believe its better then solder because when I took it off one pad has 4 arc spots on it, its galled/melted from the 4 spring contacts that bring that 'foot' of the IGBT down to that pad. It must have developed a high resistance.

What is the specification for a SMD power spring fit pad? I do have to restore it. the whole thing of using the PCB directly as a contact seems dumb. the pads are also not gold plated, maybe thats a good thing for repairs, but they appear... tin plated? Is that even good? You would think they would sell a nice base plate that you solder to the PCB then insert the IGBT into that, or at least have solder in receptacles. Why does it go directly into the PCB? Thats so janky. The design in general does not feel 'low inductance' either. I guess the springs are flat and not helix which helps, but still.

I can re-tin it with an iron, and I can also clean it up good with a solder wick.. but is that surface good enough for the semikron spring contacts after my restoration? I can also try to take the pad down to bare copper with unionized abrasives (rubber abrasives), maybe, and then plate it myself, either with rub on silver or some kind of electroplating pen sponge thing. Do you think retinning, solder wick mop job is good enough for a contact? It looks too dull to be nickel on the pad.

This whole deal seems bootleg for a tig welder.  Maybe I am not getting something, but tin is just as soft as gold, and 'digging in' won't really hurt the igbt, the spring tips are rounded and free, if it shifts a few thousanths to 'pull them side ways' i don't think any sort of plating would get in the way and for some reason its difficult to imaging something bolted on with 2 1/4 inch bolts sliding around gracefully between the surfaces . I think if it was gold plated maybe this fault would be avoided, or if it had a real receptical thats not a PCB pad covered with tin.


most multimeters use gold plated contacts. I don't see why you can't use gold here. it seems like the same concept. I almost want to get a gold plating brush and plate the pads myself

T3sl4co1l:
No, solder will not restore it.  It's junk, replace the assembly.

Tim

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