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April 8, 2015 | Kevin Balben, DELOEstimated reading time: 1 minute
Protecting electronic components from thermal, mechanical and chemical stress is becoming increasingly important in many industries.
While application-friendly packaging is one way to ensure components’ stability, highly reliable encapsulants are playing a more important role as well.
DELO Industrial Adhesives’ product specialist Kevin Balben explains the correct uses of today’s encapsulants and compounds and clarifies the myths that surround them.
True or False?
When using encapsulants and casting compounds in electronic production, there is no alternative to heat curing in ovens.
True. While users have a choice between heat curing and light curing, the latter is used in a handful of applications including those that use connectors, switches and relays. Light curing acrylates are ideal for these applications and enable extremely short cycle times.
As soon as components are exposed to harsh environmental conditions, heat-curing epoxy resins are the only game in town. These robust products contain an anhydride hardener activated by heat. Therefore, curing requires temperatures between +100°C and +180°C.
For demanding conditions there are no alternatives to heat curing. Thermodes and induction are forms of heat curing and work faster than a normal oven, but are still slower than light curing. Users cannot always use induction or thermodes because the geometry and size of the parts may not allow it. For the most part, there is no way around air convection ovens.
Temperature and freedom from tensions are conflicting goals when trying to optimize the curing process.
True. The higher the temperature, the faster the adhesive cures. Thus, high temperatures are good for fast processes. At the same time, high tension causes a great deal of warping since the polymer network is created through heat and shrinks during cooling.
If warping is too intense, the materials should be cured at lower temperatures for a few minutes more. Unfortunately, there is no rule of thumb, so keep in mind that every component and assembly must be assessed individually.
Editor's Note: This article originally appeared in the March issue of SMT Magazine.
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