Being an entirely cloud-based solution, yieldHUB’s Part Average Test (PAT) solution lets you avoid program updates or updates to tester software. It is expensive to update programs as it takes up engineer and tester time. It should be avoided when possible. And it is possible to avoid it when PAT is done in the cloud. Using a Web GUI, you just tell the system which tests are for PAT. This triggers server-side scripts to look after the whole process and report back on the PAT performance of your wafers and lots for approval and update of the wafer maps which are then sent on to assembly. This allows us to dramatically lower the true cost of Part Average Testing for wafer sort.
Part Average Testing (or PAT) is required by automotive customers and also some other tier one electronics companies. The requirements for PAT testing are described in AEC – Q001. Some of our customers also use PAT for improving the reliability of non-automotive products.
The quality standard describes two approaches, “Static PAT Limits” and “Dynamic PAT Limits”. Both are included in yieldHUB.
In this case, historical data is reviewed in order to set new test limits which are intended to remove (by failing) devices which are outside of the normal distribution but would have passed by being inside the specification limits. The algorithm for calculating these is given in the standard. We developed a software module which calculates static PAT limits in a few moments. These limits can then be implemented on the test floor.
Using Dynamic PAT Limits is preferable as the limits are calculated on the actual material being tested. This means that lot-to-lot variation is not an issue. There are two places in the supply chain that Dynamic PAT can be implemented, at Chip Probe and at Final Test.
Dynamic PAT at Chip Probe is very efficient and implementation is quicker and easier than at final test. yieldHUB’s solution for Dynamic PAT at probe is standard and can be included as an additional tool with any of our products.
yieldHUB is a trouble-free/low maintenance solution for implementing the AEC – Q001 requirements at probe. There are no program updates, separate DPAT limits for each site are set-up automatically and there is a full record of all limits applied. A report is provided per lot and each lot can be signed-off by engineering before the assembly maps are sent on.
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