Würth Elektronik believes it can help attach ICs to a densely populated circuit board with the ESC (encapsulated solder connection) process. The process is suitable for the most diverse substrates, says the company, citing examples of fragile glass materials, FR4 or even flexible materials such as polyimide foils or LCP (liquid crystal polymer). Depending on the substrate, extremely tiny pitch distances of less than 100µm can be realised. Using thermal compression bonding technology, the upside-down chip, or flip chip, is set onto an anisotropic adhesive containing microscopic soldering particles. Briefly heating the adhesive melts the solder particles to solder the chip's contacts and the substrate. The simultaneous hardening of the epoxy adhesive also sets the flip chip into place. An additional underfill process is not required. The precision of placement and the finely dosed bonding force make it possible to process even extremely brittle substrates without any problems, claims the company. The company has demonstrated common surfaces, such as chemically applied silver, chemically applied zinc, ENIG (electroless nickel immersion gold) or ASIG (autocatalytic silver immersion gold) can be used in addition to its use in the Lasercavity method, which the company is pioneering.
