Conventional PCB design substantially differs from the design of a high-speed automatic test equipment (ATE) PCB. It’s better known to semiconductor companies as a “test board” that tests and verifies the functionality and operation of a newly developed chip like an advanced system-on-a-chip, FPGA, µP or other highly prized integrated circuit.
The device-under-test or DUT area of the ATE PCB is the main difference between it and the conventional PCB. Considerable and careful design attention goes to the DUT area. Here, the DUT is characterized by high-speed 30-40 GHz and beyond ATE PCB traces and trace length matching. Plus, the designer deals with curve routing and loop back traces, which can be challenging.
The semiconductor customer ordering a specific test board provides the information relating to the high-speed traces. Most often, they are assigned in the schematic or provided in the specification sheet. That data includes the number of high-speed traces in the design and designates the ones that are serial/deserializer (SerDes), loop back, and SerDes with capacitors.
Unlike conventional PCBs, ATE PCB design takes considerably savvy to know and deal with a number of nuances. You can read more detail in our article, Key Design Steps for DUT Areas on ATE PCBs.
In the meantime, here are some tips and hints to help you get better acquainted with ATE PCB design.
- Loop back traces go from and to the pin of the DUT, typically a BGA package.
- For the high-speed SerDes trace, the via pattern is placed close to the socket so that the trace coming from the BGA to the via and then again from the via to the BGA pin.
- The third type of high-speed trace involves routing SerDes with capacitor. The trace routing is terminated on the two pins of the two capacitors. Then, again, traces are routed again back to the BGA pin.
- Lesser value and smaller capacitors are placed on the BGA because they have a faster response time.
- Keeping the decoupling capacitor close to the BGA pins is one technique for improving high-speed signals.
- Curve routing, shown in Fig. 1, is necessary to maintain signal integrity and avoid signal discontinuity for signal transmission and reception.
The design of an ATE PCB includes the basic conventional steps of a routine PCB design. But when it comes to the DUT for an ATE board design, there are several key and major techniques that must be perfected for the high-speed traces and trace length matching. Also, the ATE board designer must fully understand and implement curve routing and loop back traces. All in all, correctly factoring in these steps makes for a highly reliable ATE board design.