Sanded chips

[Austinthemighty]

Why do some manufactures sand the top of there chips
for example, if you look at this board all three of the chips have been sanded
 

[fourtytwo42]

This has been going on for donkeys years, its just one way of obscuring the design, making it more difficult for others to copy, I used to do it to power transistors in my amplifiers before time began

[timb]

It’s a lame attempt at preventing you from reverse engineering the design. It rarely works out, however, as a skilled engineer can generally figure out what the chip is anyway simply by function, package and tracing the connections. Failing that you can always dissolve the chip package and look at the die itself, which will sometimes contain identifiers.

[CM800]

It's very common on stepper drives and controllers from Asia, Leadshine expecially.

often  they do a half arsed job of it, if you rub some thermal paste into it, you can read most of it sometimes.

[Bud]

Because there is a big nation of thieves living somewhere in Asia. They steal from the West and then steal from each other. They sand chips trying to prevent their brothers to steal from them.

[CM800]

Because there is a big nation of thieves living somewhere in Asia. They steal from the West and then steal from each other. They sand chips trying to prevent their brothers to steal from them.

It's open source hardware, but you have to work for it.   

[Mr. Scram]

It’s a lame attempt at preventing you from reverse engineering the design. It rarely works out, however, as a skilled engineer can generally figure out what the chip is anyway simply by function, package and tracing the connections. Failing that you can always dissolve the chip package and look at the die itself, which will sometimes contain identifiers.

The problem with the method is that you will catch out amateurs, but will hardly slow down organised copycats.

[technogeeky]

I want to point out that it's also a hint that the volumes on the assembled device are relatively low. If they were high, the manufacturer could easily ask for parts with their own label and/or part number on the ICs (probably for free or almost for free). In this way, they could hide the part identification for the device without looking amateurish and without paying for the cost of someone to drill/sand it off, or the time required to put the device or IC in a jig to laser etch it off.

So it's only used for relatively low production volumes, and it only defeats relatively low skilled or low effort reverse engineering attempts. Low skilled because it's not difficult at all to take a completely populated board with labeled ICs, depopulate the board, and completely reverse the thing. I could do this, and I'm barely beyond monkey level intelligence. Low effort because, many ICs are labelled with identifying information on-die, so a hot plate, some fuming nitric acid, and a decent microscope are all that are needed to overcome this.

[Zero999]

I used to do it to power transistors in my amplifiers before time began

Oh dear, that was lame. Only a couple of seconds with a transistor tester will identify them. A 5 year old could do it.