Ask HN: Why do we bother screenprinting mass-produced PCBs?

I was reading the recent front-page article on Apple power supplies[0], and this image[1] caught my attention.

I’ve been used to seeing white screen printing on PCBs, never really asking why. But… why? Between the ink for billions of PCBs produced every year, plus adding the screen printing step to the process, these have to cost some real money for something no customer really cares about.

Maybe it’s useful for development, return-from-field debugging? Maybe for alignment of automatic pick-and-place machines?

Just curious what the tradeoffs are in reality.

[0]: http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html?m=1 [1]: http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html?m=1