Die attach adhesive boosts placement precision
DELO has launched a new fluorescent die attach adhesive to replace its previous material for securing silicon die to printed circuit boards and other substrates.
The MONOPOX EG2596 features high strength even after aging and can be dispensed even more precisely than its predecessor. This has been shown in tests in conjunction with the machine integrator ASM Assembly Systems. The fluorescent adhesive is suitable for long-term use in a wide range of applications.
Adhesives are used on printed circuit boards not only for fixing components, but often also for electrical insulation. They are frequently required to be temperature-resistant and to offer good dispensing properties to meet the increasing miniaturization requirements.
The new die attach adhesive replaces the current MONOPOX MK096 and is well suited for long-term use. Like its predecessor, it is a heat-curing one-component epoxy resin. The new adhesive exhibits a 150 % higher strength after seven days of storage at 85 % relative air humidity and a temperature of +85 °C. It maintains its strong adhesion even after typical aging tests, like the MSL1 test, in accordance with JEDEC standard. When using 1×1 mm² silicon dies, the test revealed adhesion values of 47 N on FR4 substrate and 62 N on gold.
Another advantage of the EG2596 is a high thixotropy index of ~ 9. The higher the index value, the more flow-resistant the dispensing pattern after the dispensing process. The thixotropic properties ensure that the adhesive can be applied very finely in a low-viscous state due to the shear in the dispensing valve. After dispensing, viscosity increases again in fractions of a second, preventing the adhesive from flowing. This allows the die attach to be built up in individual droplets and then shaped in a controlled manner, without the adhesive spreading into areas that should remain adhesive-free. Even during heat curing, the adhesive drop remains dimensionally stable.
The flow properties of the adhesive are designed to allow dispensing by means of jet valves and needles, providing more versatile application options. Tests conducted jointly by DELO and its technology partner ASM Assembly Systems, a global manufacturer of SMT placement machines and solutions, show the dispensing properties of the die attach adhesive – using, among other dispensing systems, the “Glue Feeder”. This jet valve allows the adhesive to be dispensed contactless and upside down. The adhesive is applied directly to the specific component and not to the printed circuit board, a solution that ensures fast and highly precise processes. Depending on the dispensing equipment, drop sizes down to below 250 µm can be achieved. Even after several shots, the dispensing patterns remain uniform and do not show typical unwanted effects such as satellite droplets.
Curing takes place at +130 °C in 10 minutes. The fluorescent adhesive is available in 10 cc cartridges and can be ordered in quantities of just one. Once opened, the product can be processed in a user-friendly manner for up to seven days in a standard climate of +23 °C.
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