The use of light for therapeutic applications requires light‐absorption by cellular chromophores at the target tissues and the subsequent photobiomodulation (PBM) of cellular biochemical processes. For transdermal deep tissue light therapy (tDTLT) to be clinically effective, a sufficiently large number of photons must reach and be absorbed at the targeted deep tissue sites. Thus, delivering safe and effective tDTLT requires understanding the physics of light propagation in tissue. This study simulates laser light propagation in an anatomically accurate human knee model to assess the light transmittance and light absorption‐driven thermal changes for eight commonly used laser therapy wavelengths (600–1200 nm) at multiple skin‐applied irradiances (W cm−2) with continuous wave (CW) exposures. It shows that of the simulated parameters, 2.38 W cm−2 (30 W, 20 mm beam radius) of 1064 nm light generated the least tissue heating −4°C at skin surface, after 30 s of CW irradiation, and the highest overall transmission—approximately 3%, to the innermost muscle tissue.

A simplistic simulation technique has been developed for computing the individual intermetallic compound (IMC) thickness which is formed in substrate-solder (Cu-Sn) systems during the diffusion soldering process in high-temperature power electronic applications. The method requires the time-dependent temperature profile for the soldering process and the growth rate parameters (e.g. concentration gradient, diffusion coefficient, activation energy, etc.) for the development of IMC layers as input. The method is suitable for predicting the thickness of an intermetallic phase layer during the diffusion soldering process. As such, it can be used in high-temperature power electronic application's solder processing to enhance the reliability and lifetime of solder interconnections by allowing the control of the thickness of IMC layers. The method is demonstrated for IMC growth between pure copper as substrate and pure Sn as solder material. The growth behavior of the IMC layer is increased with increasing temperature over time according to the Arrhenius theory in the temperature range between 24°C to 260°C. To simulate the formation of IMC thickness in diffusion soldering interconnections, a simplistic way has been attempted using the popular commercial finite element simulation tool Comsol Multiphysics and scientific computing application 'Matlab'. By means of transient thermal input, the diffusion-controlled intermetallic phase formation is simulated here. Few assumptions are taken care of this simulation process, for example, no convection, no reaction, solid-solid diffusion, no the pressure effect on the computational domain.