Specialty Chemicals, Adhesives & Plastics
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LOCTITE ECCOBOND EN 3838T is a black epoxy encapsulant that is designed to provide a flexible, low Tg material for encapsulating components on a PCB. When cured, this material provides physical protection and stable electronic performance and protection in temperature/humidity/bias testing.
LOCTITE ECCOBOND EN 3838T is a single component, reworkable, heat curable PCB coating that cures fast at moderate temperatures and is typically used for CPG and BGA lead free applications.
Both 3838T & 8387B have a rather high thixotropic index and this indicates a low amount of self-leveling (the viscosity at low shear rates is too high to allow the material to move under its own weight). When we compare the viscosity data on TDSs, we see that they are measured using different spindles and at different rotation speeds. The reason for this is, that 8387B is developed for smaller deposits in die attach and sensor bonding applications (less weight to move the product), while 3838T is developed for larger deposits with higher thixotropy to prevent running out. Based on the viscosity data, we see that ‘viscosity almost at rest’ of 3838T is higher than 8387B :
One way to reduce the viscosity (at all shear rates) is to increase the temperature of the product and or substrate. Warming to ~40C will give a big difference in viscosity (every 10 °C double or half). Going much higher in temperature could give some gelling, but customers should establish the best temperature by experiment.
LOCTITE ABLESTIK 3838T should be able to cure, based on this DSC curve, at around ~110°C (lower than that can be risky). A starting cure time can be 30 min but we advise to optimise it for your requirements.