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I've seen lots of products with hand painted dots or markings on chips, what do they often mean? Obviously I understand everybody has their own reasons but could it be an industry common practice for QA or programming?

For example, this picture of an Xilinx CPLD has two painted dots. I've also seen ones where it's a sloppy line on the middle of the chip.

(Image source Wikipedia)

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    \$\begingroup\$ Those appear to be paint pen markings, so they could indicate anything and your question is likely to produce opinion based answers. That said, it could be a marking to indicate the device has been verified at some stage of quality control. It could also indicate a firmware update or just about anything else though. \$\endgroup\$
    – K H
    Mar 26, 2021 at 7:42
  • \$\begingroup\$ @KH Do you have any idea what sort of paint those are? I've tried a few "permanent" markers, but those just wash off with Isopropanol. \$\endgroup\$
    – Arcatus
    Mar 26, 2021 at 21:04
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    \$\begingroup\$ @Arcatus they're called paint markers or paint pens. They dispense a fairly hard drying and durable enamel. Nail polish is sometimes used in the same places. They're sometimes called valve markers. The brand I like is Markall. If you want ritzy markings on your tools, use a dremel to engrave your initials 1 9mm deep on flat metal, then fill the groove with paint pen enamel. Very factory looking, very permanent. \$\endgroup\$
    – K H
    Mar 26, 2021 at 21:14
  • \$\begingroup\$ Lol 1 mm. Apparently autocorrect thinks "9mm", a phrase I never use is the logical replacement for "mm". \$\endgroup\$
    – K H
    Mar 26, 2021 at 21:36

3 Answers 3

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These are put there during assembly and test of the PCB and can mean anything the manufacturer wants to mark.

Often such a dot is put on a microcontroller, when the firmware is successfully programmed into memory. It can also mean, that the device passed all the tests during production.

Whatever the dot means: It is a sign for the manufacturer, that certain steps are done. This makes it easily visible if a board is ready to be processed further, or packaged, or ...

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    \$\begingroup\$ That chip is a CPLD, so I think you nailed it. Yellow dot after successful programming, white dot after successful testing seems the order in this case. Likely that happens before board assembly - the dots are probably added by the machine that programs and tests the CPLD and the dots are likely checked by the pick-and-place system laying out the board as a QC step. \$\endgroup\$
    – J...
    Mar 26, 2021 at 18:00
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In the analog (especially RF) World, similar dots could signify passing different performance specifications at the component QC level. Different component specs might be sold at different price points and/or used for different applications. But similar dots might be added later at the PCB level of manufacturing just because it's a convenient flat spot. As previously stated, they can mean whatever is useful to the manufacturer. Always consult the manufacturer when in doubt.

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I worked with an electronics engineer who built a new amplifier with digital and analog chips. To protect the design he ground off all identification on the chips and color coded the chips with paint dots for assembly.

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  • \$\begingroup\$ Which typically is not very effective... It for sure makes repairs harder, but if any company has reasonable interest in reverse engineering the product the ICs can often be identified quite simply by analyzing the pinout. So it offers no protection of the IP and only makes repairs more difficult. Great thing! \$\endgroup\$
    – jusaca
    Mar 27, 2021 at 10:42

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