WLCSP Damage..

[Timp74]

How sensitive are WLCSP packages to damage?

The photo is of the Audio/Headphone CODEC on a Macbook a2485 820-02100 motherboard. The motherboard doesn't power on, possibly because this chip is holding the PP1V8_AWAKE rail down. It's not shorted, just the 1.8v rail going into it only comes up to about 0.7v, then resets. Which I think is stopping the machine powering up fully. There are a few other chips on the same rail but they all look fine.

Anyway, if anyone has an opinion on WLCSP chips I would like to hear it. I've used Intel CPUs with chips/scratches in the die without problems. I read that on flip chips the circuit isn't near the top/edges of the die. Is that also the case for WLCSP chips?

Just as a warning. I damaged the chip while trying to reinstall the motherboard. The a2442 and a2485 macbooks have a load of push fit connectors on stiff ribbon cables for the USB ports, speakers and mag-safe connectors. These catch on the motherboard and seems they can damage the components on the the motherboard quite easily. Probably a good idea to tape them out of the way when removing or installing the motherboard on these Macbooks...

[mon2]

Re: WLCSP Damage..

Are you saying this board worked fine till this small damage on the top surface of the WLCSP device ?

We design with WLCSP devices all the time and yes, they are brittle and delicate devices. We have a small Lattice ICE40UL1K in a 16 ball WLCSP package we use in a 8 pin DIP package. Can solder then in our sleep after lots of practice. If not expensive, consider to replace this device.

[Timp74]

Re: WLCSP Damage..

Are you saying this board worked fine till this small damage on the top surface of the WLCSP device ?

I was trying to fix the backlight circuit, but once I had worked on that, the laptop wouldn't power on. After diagnosing the problem, it looks less like it's because of my work on the backlight circuit. So I've been looking at other damage on the board. This is the only chip on the power line that's not working properly that has damage. Although it's not much damage, so that's why I want to know about people's experiences with WLSCP chips.

[mon2]

Re: WLCSP Damage..

See attached. The 1v8 power rails on this WLCSP are through 2 x series FB devices.

With flux and low air pressure, carefully remove each or shift each so that they are not mating to the other contact. This will remove the 1v8 rail to the WLCSP device.

After you do this, check the resistance to ground again for this power rail to confirm if this WLCSP is the guilty party or not.

PS: Do not power up unless you ALSO remove LR500 & LR503 which are other power rails to this WLCSP device. We are only wanting to check if the 1v8 is impacted by this device. if you remove LR500 & LR503 then this CODEC will not be powered.

It is possible that being an I2C bus slave, the host OS is attempting to ping this I2C address and perhaps due to this small topside chipping, the CODEC is not responding.

Post your updates.

PS #2 - unable to find this bad boy on Aliexpress No idea how this CODEC is selling for.

[Timp74]

Re: WLCSP Damage..

See attached. The 1v8 power rails on this WLCSP are through 2 x series FB devices.

With flux and low air pressure, carefully remove each or shift each so that they are not mating to the other contact. This will remove the 1v8 rail to the WLCSP device.

After you do this, check the resistance to ground again for this power rail to confirm if this WLCSP is the guilty party or not.

PS: Do not power up unless you ALSO remove LR500 & LR503 which are other power rails to this WLCSP device. We are only wanting to check if the 1v8 is impacted by this device. if you remove LR500 & LR503 then this CODEC will not be powered.

It is possible that being an I2C bus slave, the host OS is attempting to ping this I2C address and perhaps due to this small topside chipping, the CODEC is not responding.

Post your updates.

PS #2 - unable to find this bad boy on Aliexpress No idea how this CODEC is selling for.

Thanks for your help on this. Much appreciated. I removed the two inductors as suggested, but it doesn't seem like the audio WLCSP chip is the problem on the PP1V8_AWAKE rail. There's no short on it, it just doesn't come up okay. I think I may have damaged the slave PMIC buck controller U7700 while trying to fix the backlight boost controller. It's a mystery how. There is no direct connection between the two chips. I'm still hoping I'll find something else I damaged while installing the motherboard which explains the problem...

If I ever get the motherboard working again I comment about if the CODEC still works with that chip in it...