Frequently asked questions on over - moulding
- Can you over-mould a PCB with surface mounted components?
Yes, we have over-moulded hundreds of different PCB’s without damaging boards/components or reflowing solder. Tests show that material injected at 218°C (425°F) typically will cool down to less than 150°C (300°F) by the time it reaches the board.
- Is the final component distorted in any way with this process?
No, not if proper 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).
- Will the part maintain dimensional stability after moulding?
Shrinkage ranges from 1 to 1.5% for the different Macromelt materials.
- How can air bubbles be avoided in the final moulded part?
Ensuring that the mould-set is vented correctly and optimising the injection profile is the key to avoiding air bubbles. Densely populated circuit boards may require several steps in the injection profile to avoid any “shadow effects” behind components. We would typically start by optimising flow with translucent materials to detect where voids occur and then change to black materials for production.
- Can batteries be over-moulded without reducing their effectiveness?
Many types of batteries have been successfully over-moulded with Macromelt. However, simple prototype over-moulding for a particular battery is recommended before starting full-scale production.
- Which wires, cables, circuit boards and solder masks do these materials adhere to?
Macromelt® adheres well to most substrates including PVC wires and PCB’s. Henkel Corporation offers adhesion testing of their Macromelt® materials on any specific substrates; this type of testing will identify the most suitable material for a given application.
- When should this technology be considered for grommets and strain relief moulding?
The adhesive properties of the Macromelt® material will offer great seal and strain relief to most wire and cable materials. When true strain relief is needed especially for sensitive cables/applications such as Cat 6 patch cords and connectors, the Macromelt® materials are superior.
- Are over-moulded parts water proof?
Over-moulded components will typically meet or exceed IP 67 rating for the type of environment it is capable of operating in. This means they are dust tight and protected against the effects of immersion. The selection of Macromelt® material grade is critical as there are different degrees of water resistance.
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