Is this board salvageable?

Thread Starter

berni29

Joined Apr 6, 2021
16
Hi

I posted previously and was kindly helped to identify a blown SMD component (inside a brushless drill motor).

However, now that the blown component is removed I am left with this. It actually has 15 contact points as per the picture below.

I would love to fix this. Is it time to give up?

Many thanks

Berni
 

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SamR

Joined Mar 19, 2019
3,498
Possibly, but I suspect from the extreme failure of the one component that others were also affected and may also be damaged. Try and see...
 

Reloadron

Joined Jan 15, 2015
6,067
I have to agree with SamR:
Possibly, but I suspect from the extreme failure of the one component that others were also affected and may also be damaged. Try and see...
The damage you see and a blown or smoked component is likely just a symptom. You could replace it and have the same thing repeat. There is a reason that component smoked. "Déjà vu all over again" to quote Yogi Berra. :)

Ron
 

narkeleptk

Joined Mar 11, 2019
540
Replacing it like that will be fine as far as the igbt goes but you may or may not have other problems. One things for sure we do know this igbt is bad so its a good place to start!
 

Irving

Joined Jan 30, 2016
2,112
You have 3 phases in the motor and 6 igbt, 2 per phase. It's likely the other igbt on this phase, if not dead, has been badly stressed and it's good practice to change both at the same time. Assuming no other faults that is... Without suitable test gear it's going to be a suck it and see job. How much are the replacement igbts?

How did you remove the old part? It looks like theres still much of it there..
 

Thread Starter

berni29

Joined Apr 6, 2021
16
You have 3 phases in the motor and 6 igbt, 2 per phase. It's likely the other igbt on this phase, if not dead, has been badly stressed and it's good practice to change both at the same time. Assuming no other faults that is... Without suitable test gear it's going to be a suck it and see job. How much are the replacement igbts?

How did you remove the old part? It looks like theres still much of it there..
Hi Guys, thank you very much.

Irving, I masked off the other components with tin foil and used a hot air gun. I did not want to over heat things and di not actually see any solder melt. The metal lid did fly off and I scraped the rest off. I assumed the whole component had come away, but maybe not! It looks like there is a copper base which I assumed was damaged circuit board. It does not make sense that it is copper or else it would short out between the contacts.

I shall get the microscope out and have a proper look.

Thanks again

Berni
 

MisterBill2

Joined Jan 23, 2018
9,308
OK, but the concern is still valid that probably at least one other component has failed. We did not see the rest of the assembly to know what other parts are present. Often, when a part fails, there is a reason that it failed. And often that is because another part ha also failed.
 

Thread Starter

berni29

Joined Apr 6, 2021
16
OK, but the concern is still valid that probably at least one other component has failed. We did not see the rest of the assembly to know what other parts are present. Often, when a part fails, there is a reason that it failed. And often that is because another part ha also failed.
Hi yes, I agree absolutely. Here is a pic of the topside of the board. It does not look like it is designed to come off the motor easily. The underside has hidden components. I had a look through the gaps but could not see anything that was obviously blown. I have an inspection scope which might offer a better view. I will try that.......

Tks again

Berni
 

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narkeleptk

Joined Mar 11, 2019
540
I think you where better off before, looks like your just butchering it now. I'm not entirely sure there was anything left in your first picture, the quality makes it hard to tell but It would have been easy to know with it in front of you because it would have been slightly higher then the solder mask.
 

MisterBill2

Joined Jan 23, 2018
9,308
There are quite a few failure modes that do not show on the outside and that is why more than an inspection i usually required. In many circuits the failure of some part will then lead to the destructive failure of another part. So if a replacement assembly is available at a reasonable price replacing the whole thing would be a better choice.
 

Thread Starter

berni29

Joined Apr 6, 2021
16
Hi There

If there were a replacement board available at a reasonable price I would certainly be interested, but sadly it is not, and the cost of the motor $300) exceeds the cost of a new complete drill.

I'm curious why under the removed component there is a sharp cutout with no contacts. Why is that? Usually there are tracks on the board, but I guess these ones run inside or something?

So does it look like the board is destroyed and it's the end of the road? Is it time for me to give up, or can anyone suggest a way forwards.

Thanks again

Berni
 

narkeleptk

Joined Mar 11, 2019
540
Its never too late.
The connections are very simple. You only have Drain,Source & Gate despite all the pads. Looks like there is still enough there to work with just stop removing material and lay it back flat, flux the pads, tin them, tin the mosfet and hot air it down. See what happens, Win or loose its good learning experience. My biggest concern would be the craters in the source pads, I wonder if they where vias that have now burned open. I recommend you check for that first and If so you would need to to correct that before you put the new replacement down.

Clipboard01.jpg
 
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Irving

Joined Jan 30, 2016
2,112
You need to get it flat with solder resist showing between pads as per the LH side of the pic in post# 15. To me it looks like you still have some old chip left on the RH side. Use some ChipQuick low temperature solder and lots of flux to release the joints and then wick all the solder off with a small iron and some quality fluxed wick.

After that a test meter on diode mode may give some clues as to the state of the other igbts and the motor windings. It won't be foolproof but it's a go/nogo check.

Is there a separate control board that connects to this driver board?
 

Irving

Joined Jan 30, 2016
2,112
This pic shows typical 3-phase motor drive with igbt:


Measuring between P., N and a, b, c will give some go/nogo info, assuming you can get at the relevant points.
 
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