IPC WP-028 PDF

Conformal coatings are used to increase the robustness of electronic assemblies against condensation risk and as protection against particles. The protection function is of highest priority for components with small pitch or low pin distances where the risk of bridging by water droplets or particles leading to an electric short is most critical. The trends of miniaturization and use in harsher environments combined with increasing lifetime expectations frequently requires electronic assemblies to be protected by conformal coatings.

The electrochemical performance of coated assemblies can be characterized by following the mindset of IPC-9202 test protocol where the package design effects on the ionic contamination, on the bias and on the present local humidity are taken into consideration, see Figure 1. Interactions of material and processes are evaluated during the surface insulation resistance (SIR) test using an assembled test board like B52 test PCB.