Electronics > Manufacturing & Assembly

Soldered Castellated XL51822 short

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My nordic chip's power consumption increases dramatically after soldering it to my custom PCB.
It goes from 4uA to 10000uA.

Before soldering, the resistance between ground and VCC is around 2.5 megaohms but after soldering, it sometimes decreases to 50kOhms.
It looks like my soldering is shorting ground to VCC.
Is this the cause of the increased power consumption?

XL51866 castellated chip:

Custom PCB:

Even after unsoldering, removing all solder and flux,
the XL51822 chip's power consumption remains high,
so I suppose I damaged it.
I tried on about 4 identical chips, all the same.

To measure power usage without the PCB, I use my homemade pogo pins fixture, please don't laugh :)

I've had prior success soldering ESP32 castellated modules on my own PCBs.
So I really don't understand what I'm doing wrong here.

Any suggestions ?

It looks like you just hand soldered Vcc and Gnd and that was it, hardly seems possible to damage the board just based on that.

- Sure its nothing to do with what program is loaded to the device? Did you load any code.
- What voltage are you supplying the module with? Its rated for 3.6V max

One small issue: you have uncapped vias under the module, which is not great, if they were in the wrong spot it potentially could short out to the module.

Yes I have loaded my code on it of course.
I tested it with 2 programs in fact.
One is just putting the chip to sleep, which consumes 4uAh.

The other one has bluetooth enabled.
The power usage on this one varies between 4uAh and 60uAh,
which is expected based on the advertising interval of 750ms I set.

I'm supplying 3.3v.

You are right about uncapped vias, a rookie mistake.
But I tested everything with a piece of paper between the XL51822 and the PCB, covering all pads except for VCC and ground.

OK so you did program the same code on a good new unit, in your pogo jig, and it consumes 4uA, not the bad 10mA level.

Maybe the pads on your PCB, even though they were not soldered, had connected and caused some short.
I do see those two vias under the device look unusually close together.
Seems unlikely though.

Maybe post the schematic?

As many has mentioned, the vias is probably the cause.


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