Foresite has a wide range of capabilities for environmental testing, as well as many years of experience analyzing the impact of environmental factors on reliability. Our services include:
Surface Insulation Resistance (SIR) testing
SIR testing is used to evaluate materials and processes used in the manufacture of printed circuit boards (PCBs), and to assess potential assembly (PCBA) failures due to corrosion and other problems caused by ionic contamination. The test evaluates processed test coupons in an elevated temperature and humidity environment, accelerating the effect of operating environments. Resistance measurements are taken between two electrical conductors periodically during the test; resistance measurements must exceed 1.0E+08 Ω in order to pass IPC requirements.
Umpire 2 Test Board
The Foresite-designed, Umpire 2, test board contains the comb patterns of the B-36, B-24, Bellcore and B-25A test boards and can be utilized in multiple test applications. The board consists of a main board and two breakaway coupons for different test procedures. This board is best used to qualify processes for primary (wave solder, SMT, cleaning, no-clean) and secondary steps (temporary solder mask, rework flux, rework cleaning). It also works well to look at solder mask, interactions between solder mask and fluxes and/or solder pastes, and materials characterization . The Umpire 2 component kit contains nine QFNs, two LCCs, one BGA, four Dips, one TQFP, a three pin header and a sixteen pin header.
Electrochemical Migration (ECM)
ECM is characterized by the movement of metal ions between adjacent metal conductors, to form dendrites. The key control parameters are:
- Moisture or high humidity
- Presence of mobile metal ions
- A high potential gradient, expressed in Volts per unit length (e.g. V/cm)
Elevated temperature can be another factor in ECM. The hydrated metal ions, being positively charged, will migrate towards the cathode (-ve), forming a dendrite – a needle or tree-branch-like metal structure. The dendrite is the primary visual indicator of ECM.
Dendritic growth resulting from ECM can cause electrical current leakage, and even short-circuiting, in electronics.
Temperature Cycle Testing
Temperature cycle testing is performed to determine the resistance of a device to alternating temperature extremes. The test procedure exposes the assembly or component to many cycles (typically 500 to 1000 cycles and beyond) of very high and low temperatures. The test design may employ a gradual ramp rate to the temperature extreme (temperature cycling), or an immediate temperature transition (thermal shock). The test is designed to primarily test the resistance of the assembly or component to fatigue failure modes. Fatigue is defined as the failure due to the effect of cyclical stress loads. Typically, the higher the number of cycles a device resists fatigue failure, the longer its life will be in a field application.