PCBs sit in a vehicle in sensors, the powertrain, lighting and infotainment. What separates such a board from an industrial one is written less into the stackup than into the order.
PCBs sit in numerous safety- and function-relevant areas of a modern vehicle: in sensors, in the powertrain, in lighting systems and in infotainment. Purely technically, such a board often differs less from an industrial one than you would expect.
The difference lies in what has been agreed around it — temperature profile, acceptance class, traceability and change discipline. What of that is written into the order decides how the board is built and how it is inspected.
Thermal cycling, not peak temperature
The load case that drives the design in a vehicle is rarely the maximum temperature; it is the cycle. A control unit in the engine bay goes through thousands of swings over its life, and every one of them works on the plated through-hole: the laminate expands far more in Z than the copper in the barrel does.
So the levers are in the build, not in the assembly — a resin system with a suitable glass transition temperature and low Z-axis expansion, adequate copper in the barrel, aspect ratio under control. If you know the cycle, that can be designed for; if you do not specify it, you get a design for the ordinary case.
Acceptance class is a cost decision
IPC-A-600 and IPC-6012 define three classes. Class 2 is ordinary industrial work; class 3 applies where a failure is not acceptable. Automotive asks for one or the other depending on the application — safety-relevant control units tend towards class 3, comfort electronics usually class 2.
The class does not change the design; it changes the permitted tolerances and the inspection scope: annular rings, copper in the barrel, breakout, allowable defects. That makes it one of the few points in a specification that move the price directly and noticeably. It should be set deliberately, not carried over from an old template.
Traceability and change discipline
- Lot-level traceability down to material and production lot, not just to the delivery.
- Fixed base material: an equivalent substitute is not a silent change in an automotive context, it is a notifiable one.
- First-article inspection to an agreed scope, covering the characteristics that are actually critical.
- Change notification before implementation — including a plant change within the same release.
- Process capability on the critical characteristics rather than a sample check at the end.
What that looks like in practice
Most queries in automotive projects come not from the layout but from unwritten assumptions: an acceptance class nobody set, a temperature profile given only as an operating temperature, a material release that does not cover the substitute.
Settling those before layout freeze is cheaper than any later loop. We go through them in the data check anyway — asked earlier beats explained later.