Expectations and Reality
Are promises made by your micromachining service provider actually deliverable?
Let’s say you need a probe card template made which has holes of various sizes. There is both a placement precision as well as hole size spec to be maintained. All the probe cards made by your favorite micromachining service provider has been good- no complaints from upstream process managers.
You are now working on a 8 inch version, and assume it can be done as before. The provider thinks the same, although both don’t realize that placement precision would become woefully off-mark for long travels. You neither have checked any previous parts to see if they meet specs, nor do you have the facility to do so.
The cards get made, the techs at the next stage first complain that the holes are not the right size because the probes don’t go through. You check the hole sizes (which is easy to do with a microscope) and find they are ok. Everyone wonders what is going on.
Finally, you suspect that the placement is off-spec, particularly for the out-lying holes. The service provider insists everything was done to specs, and provides documents related to stage specs to back it up. Totally lost, you send out the card to a buddy at a semiconductor house for checking, and he pronounces placement errors.
What went wrong?
Analysis: The service provider assumed wrongly that the stage specs will hold at all times. He didn’t think of it as a X-Y problem, rather as a X or Y problem separately. They had never really verified the positional accuracy of their stages, but neither did they have any complaints from customers. So they went with the specs provided with the stages and quoted it orally to the customer. Placement precision is an important factor in such projects, and numerous factors are involved. In fact, stage manufacturer themselves will not quote precision and accuracy for combination of stage- only for a nominally loaded standalone stage.
The customer thinks that the micromachining provider cleverly worded the promised deliverables to escape responsibility in case of screw-ups, and that they need to be refunded the entire amount. Meanwhile, the provider thinks that they spent a lot of time on this project- much more than usual. They believe they put in a best effort, and their quotation was for best effort.