Ordered MCUs have shorted pins

LShen.3 · ‎2021-03-26

Hello. I recently purchased STM32F405RGT6's. However, out of package and on all of the IC's that I received, I discovered shorts between pins 17 (PA3) and 18 (VSS), which I do not believe should be shorted. I have a few STM32F405RGT6's that I purchased a few years ago, and these pins are not shorted. I also noticed that the package looks different, so are the parts that I ordered a newer, different design? Are the products that I purchased defective?

Uwe Bonnes · ‎2021-03-27

Did you purchase from reputable sources? Are you sure no misshandling from your side caused the damage?

LShen.3 · ‎2021-03-27

Hi Uwe,

Yes, I purchased these from Digikey. I'm also not sure how mishandling would cause all of the IC's that we ordered to have this exact same damage.

Posted this to see if anyone else purchasing these parts had the same issue...

PMath.4 · ‎2021-03-27

How did you check the short? Have you measured with the meter leads both ways round? There may be protection diodes in the chip. Can't remember if it is STM32 or PIC32 but I've seen a chip powered and working with voltage only on I/O pins and VCC completely disconnected

Tesla DeLorean · ‎2021-03-27

If they look different, perhaps some pictures? Double check orientation

If you got them from DigiKey perhaps work with them.

As Peter notes this could be ESD protection diodes providing a conduction path to supplies. Many chips can back-power via IO pins, where the grounds are common, and the IO pin(s) drives the VCC rail.

Tips, Buy me a coffee, or three.. PayPal Venmo
Up vote any posts that you find helpful, it shows what's working..

waclawek.jan · ‎2021-03-27

Are these bare chips or already mounted on some board?

JW

LShen.3 · ‎2021-03-27

These are bare chips. I originally thought it was my soldering, but I removed the IC and also checked the chips that came out of package.

waclawek.jan · ‎2021-03-27

As others said, post pictures.

As others asked: how exactly are you measuring them, and what are exactly the findings?

As you've said you've already have them populated, what were the findings when using them?

And, as others said, you may want to discuss this with digikey.

JW

PS. To avoid any confusion: this is a primarily user-driven forum, with only casual ST presence. If you want to take your issue to ST, or want ST to comment, you have to contact ST directly, through FAE or web support form.