Safe Decapsulation Techniques Using Viton Caulk

The decapsulation process in today’s failure analysis labs can become complicated with the smaller size of the package and the surface mount methods of attachment. Some failure modes recover when a part is removed from the application and remounted after decapsulation, and some parts are simply too fragile to handle for re-mounting after decapsulation. Decapsulating the failing device in-situ (on the board or DIP adapter) allows us to analyze the part in its original mounting condition, without exposing it to additional solder temperature stress, broken wires, or tweezer damage. This poses a challenge, as the fuming acids used for decapsulation most likely will spill onto the circuit board, dissolving the package leads, damaging the resin layers, and potentially corroding and shorting the circuit board traces.

Effects of Solder Temperature on Pin Through-Hole during Wave Soldering: Thermal-Fluid Structure Interaction Analysis

An efficient simulation technique was proposed to examine the thermal-fluid structure interaction in the effects of solder temperature on pin through-hole during wave soldering. This study investigated the capillary flow behavior as well as the displacement, temperature distribution, and von Mises stress of a pin passed through a solder material. A single pin through-hole connector mounted on a printed circuit board (PCB) was simulated using a 3D model solved by FLUENT. The ABAQUS solver was employed to analyze the pin structure at solder temperatures of 456.15 K (183°C) <T< 643.15 K (370°C). Both solvers were coupled by the real time coupling software and mesh-based parallel code coupling interface during analysis. In addition, an experiment was conducted to measure the temperature difference (ΔT) between the top and the bottom of the pin. Analysis results showed that an increase in temperature increased the structural displacement and the von Mises stress. Filling time exhibited a quadratic relationship to the increment of temperature. The deformation of pin showed a linear correlation to the temperature. TheΔTobtained from the simulation and the experimental method were validated. This study elucidates and clearly illustrates wave soldering for engineers in the PCB assembly industry.

Viscoplastic Model Verification for SnPb Solder Based on Creep Tests

Heat sink assembly for a main board in a server station is built on printed circuit board by an anchor system, mounted by eutectic SnPb solder. Constant high temperature condition in the station keeps solder creeping and makes it failed eventually. To calculate the stress and predict the life of soldered anchor in the station, an FE model of anchor system is built. As viscoplastic behavior of solder depends on several factors such as microstructure of solder, temperature, load, and loading rate, model characteristics should be verified before applying it to life prediction. In this study, Anand unified constitutive equation is adapted for solder modeling and its creep behavior is calibrated and verified based on creep tests.