The challenge
This board runs a laser generator used in wafer fab plasma process tools. It handles core system control, power management, the active front end, and the failsafe and safety circuitry for generator operation. At its center is a Xilinx Zynq-7000 XC7Z035 SoC in a 676-ball, 1.0 mm pitch BGA, whose joints can’t be seen once the part is down.
The Ethernet PHY chips were customer-supplied (consigned). A component-level defect in parts like these passes visual inspection and AOI, because nothing about the solder joint looks wrong. If it isn’t caught at the contract manufacturer, it shows up on the customer’s test bench or, worse, in a fab tool, where downtime is very expensive.
What BSU did
- BGA inspection. The Zynq was X-rayed for voiding, bridging and head-in-pillow, the failure modes that hide under a large BGA.
- Electrical test. BSU runs Takaya flying probe; the customer runs functional test. Flying probe checks nets and component behavior electrically, not just how the joints look.
- Finding the root cause. Flying probe flagged failures that traced to a bad lot of the consigned PHYs.
- Containment. BSU used E2 lot traceability to quarantine the affected lot. The customer switched to a different source, and the failures stopped.
Result
BSU’s test caught a supply-chain defect on parts BSU didn’t buy, before it reached the customer’s test bench or a fab tool. The board is in repeat production, with hundreds built on a 2-week turn from full kit.
