Do hotmelt systems have to conform to special design criteria for optimum performance?

The design is one factor in the success of a hotmelt molding project. Please look at our "Design Guidelines.pdf" and the explanation "filling of a housing.pdf".

Design Guidelines
filling of a housing

What are the best materials for the construction of the molds?

7075 Aluminum (US standard 7075; European standard 3.4365) is well suited for mold-set manufacturing. Aluminum offers excellent heat transfer, i.e. short cycle times. Aluminum mold-sets are relatively soft and care must be taken not to damage the cavity surface. If the component to be overmolded has steel components steel inserts are recommended in this area of the cavity. This would be the case for connector overmolding. Mold-sets can also be manufactured from tool steel such as P-20. Steel mold-sets may have to be cross-drilled to ensure sufficient cavity cooling.

What kind of mold release is preferred?

What effect does silicone mold release have on the process? After extensive testing of a wide range of mold release agents, one product has shown superior performance. Mono-Coat E-255 from Chem-Trend Incorporated. This product is not silicone-based. We do not recommend the use of silicone-based release agents when overmolding electronic components. They can result in partial electrical insulation and non-functional components.

Can the mold be plated to eliminate mold release?

The Macromelt materials are adhesives and tend to stick to most surfaces. It may be possible to use some coating for permanent mold release, but we can not recommend any coating at the moment.

Is there any distortion of the final component with this process?

No, not if normal design guidelines are followed. (Uneven encapsulation such as a very thick material section on one side of a PCB with a thin layer on the other could result in warping.)

How are air bubbles avoided in the final molded part?

By ensuring that the mold-set is vented correctly and optimising the injection profile. Densely populated circuit boards may require several steps in the injection profile to avoid any "shadow effects" behind components. The flow of material will be typically optimised with amber materials where any voids can readily be seen and then change to black for production.

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