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I have a bunch of STM MCUs (LQFP48 package) in hard plastic trays. I need to mail small quantities of them but it is impractical to cut up the trays.

Looking for any suggestions on how to properly static and mechanically protect these chips when shipping less than a full tray. (And I find nowhere to buy empty trays either... where do the chip houses get them?)

I can 3D print something in PLA, but I suspect that is not great static protection.

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  • \$\begingroup\$ I don't think you would be willing to pay for empty trays. I imagine they are quite expensive. Even little ESD cardboard boxes seem to cost a fortune. \$\endgroup\$
    – DKNguyen
    Commented Jun 2, 2022 at 19:30
  • \$\begingroup\$ Yes, the tray itself is the ESD protection -- it is what is in contact with the device leads. I see there are some ESD PLA materials out there, although very expensive. I also see some ESD sprays like Techspray ESD coating, but it is almost as expensive as the PLA. \$\endgroup\$ Commented Jun 2, 2022 at 19:56
  • \$\begingroup\$ I'll be surprised if you can't get some kind of 3d-printable carbon-impregnated plastic that would be suitable for ESD protection. Are you sure cutting up the tray is impractical? That's what Digikey has done when I've purchased small quantities of parts that come in trays, and I think Digikey knows what they're doing when it comes to distribution. \$\endgroup\$
    – Hearth
    Commented Jun 2, 2022 at 20:09
  • \$\begingroup\$ Thinking out loud - get a plastic or cardboard shipping tube slightly bigger than the chips. Spray inside & out with anti-stat spray (must be dry before sealing.) Cap/tape one end closed. Insert round anti-stat foam, chip, foam, chip... foam, compress well, cap/tape end closed. Even if dropped, only the chip corners can touch the tube. Pins could be bent slightly though; tray would be best - could stack cut-out trays in a tube. Such tubes are nice because they can be very strong (get thick ones.) \$\endgroup\$
    – rdtsc
    Commented Jun 2, 2022 at 20:23
  • \$\begingroup\$ You really can't take a hacksaw or razor saw to the tray? Maybe debris is a problem. \$\endgroup\$
    – DKNguyen
    Commented Jun 2, 2022 at 21:29

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LQFPs are pretty tough. Placing the chips in an antistatic bag, then in a layer of foam, finally between layers of cardboard should be sufficient if you mail them as a letter.

You could mail them in a typical Priority Mail or similar mailer without the cardboard. Still, keep the foam to prevent the chips from rattling around.

I suggest adding a desiccant pack in the antistatic bag to reduce moisture absorption during shipping.

Speaking of which, because the chips were removed from their sealed tray pouch they will need to be baked first before applying them to the board. Baking drives out moisture from the package. If this isn’t done the package can ‘popcorn’ during reflow heating due to the trapped moisture.

That’s also true of the chips in the trays you opened. They need to be baked first before being subjected to reflow.

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  • \$\begingroup\$ To add to this, I would often receive samples of LQFP's sandwiched loose in antistatic foam in a clamshell case and never say any issues. \$\endgroup\$
    – Bryan
    Commented Jun 2, 2022 at 21:31

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