Loss of function after exposure to high temperature (VL53L0X ToF sensor)

[philipw]

Hi everyone,

I have a problem with the VL53L0X Time of Flight (ToF) ranging sensor, where after being exposed to a temperature of 100°C for around 1.5h, the sensor is not functional anymore.

In the solder reflow process section of the datasheet, the temperatures for soldering are all well above 100 °C, so the sensor should survive these conditions.tim

Could the temperature still be the reason for the failure?

Thanks in advance and kind regards

Philip

[TDK]

Reflow is meant to be a very controlled, limited duration (several minutes), one-time event. If you kept the sensor at those temperatures continuously, it would surely be destroyed.

It's reasonable for 100 C to destroy the sensor. Max storage temperature is 85 C.

Typically, max storage temperature on chips is much higher than this, which leads me to believe there's something internal that shouldn't be getting above 85 C.

Max operating temp is 70 C. It wasn't powered, was it?

[philipw]

No, it was not powered during the heating event. 

Storage conditions in my books is for longer periods of time, say days/weeks/months. Is there any information about exact times at exact temperatures that the sensor can withstand? It's minutes at 150-250°C for soldering, unlimited at <85°C for storage, but what about 85-150°C ?

[TDK]

If it's not in the datasheet, no guarantees are made for that temperature range. You'll have to do your own testing/verification if that's something that is important to you. Unlikely that the manufacturer is going to guarantee any values outside of the datasheet, especially if you're not a major customer.

[John E KVAM]

While heating a part up to 100 degrees C while unpowered is certainly beyond the spec in the datasheet, I'm thinking this alone did not cause the failure. More than likely it would have survived. During our longevity testing we subjected the part to worse than that and had no failures. I'd look for something else. Rapid heating might have caused it. 

But if it's likely to happen again I might suggest the VL53L4ED. 

It's pin compatible, and the software function calls are nearly the same (although much simpler). Field of View is 18 degrees (vs 27) and the distance is limited to 1.3 meters - although it can spot people to the full extent of the 1.3 meters.

The VL53ED's main feature is that we have specs to 105 degrees C. Granted the VCSEL does not work as well at those extreme heats, but the sensor will survive. 

[philipw]

Hi John,

thanks for the info, I would have been surprised if the sensor is that vulnerable to high temepratures.

It was not heated rapidly, the temperature change from room temperature to 100 °C takes place over several minutes which is definitly in spec (max. 3°C/s).

The heating is part of the integration process of the sensor into a bigger system, so it will only have to endure it once during its lifetime. But if we don't find the source of the failure, I will consider switching to the VL53L4ED.

[philipw]

I just spoke to our technician and he informed me that we need to remove the protective Kapton film on the sensor before the heating/integration event.

Could this be the cause of the problem? Is the Kapton needed for thermal protection?

[John E KVAM · Accepted solution]

That Kapton tape was only there to prevent debris from getting into the holes during the soldering process. If you are done getting the board dirty, feel free to remove it. 

But the tape - and the part - are perfectly capable of withstanding wave solder temperatures. 

So I would have expected no issues. 

IN our tests the chip and the tape survive 3 reflow operations. (One might need that many when using a interposer board to lift the sensor up closer to the coverglass.) It was one of our design criteria. 

But feel free to try it. It won't hurt anything. 

- john