In a discussion with Teledyne DALSA about their MIDIS MEMS process, we spent a few moments discussing how the ASIC die and the MEMS die are mated together. With this technology, the MEMS die has landing pads and the ASIC die gets micro-bumped and flipped and mated to the landing pads.
The question was whether this was done wafer-to-wafer or using known-good dice. The answer was wafer-to-wafer, since yield allows it and the costs are much lower. All pretty much reasonable reasoning.
But then we turned into somewhat more surprising territory. The reason it’s cheaper is that it’s a whole lot easier for a robot to take a wafer, invert it, align it, and stick it onto the receiving MEMS wafer. If you take a known-good-dice approach, then you first have to test the ASIC wafer to figure out which ones are good, then saw the thing up, and then pick out the good dice. You then have to place them on the waiting MEMS dice (which would presumably still be in full wafer form), placing them only on MEMS dice that have been shown to work by whatever testing could be done at the wafer level.
This is a lot of work and requires much more worker intervention than the robotic wafer-to-wafer process. More specifically, it requires more workers. Which costs more. We’re used to casting aside jobs with technology because, in the emotion-and-ethic-free world of finance, the dollar (or your favorite currency) is king and is all that matters. If jobs suffer while I make more money, it’s not my problem (because it’s not my job suffering).
It was as if they wanted to address this potential conscience twinge that they went one step further to justify the fewer-workers approach, and it went like this: These things are assembled in Southeast Asia. Southeast Asia has a bad reputation for employing child laborers. So by eliminating the jobs, we reduce the problem of child labor.
Bet you didn’t see that one coming! Nice to know we’re doing something good for the world…