The moulding compounds used are called ‘hot-melts‘ and are typically polyamide materials that are heated to 210C, forming a low viscosity material that can be injected at typically 50 – 200 psi into the mould cavity to encapsulate the electronics.
The injected material starts cooling as soon as it comes into contact with the mould cavity, thereby producing a short curing time cycle. The excellent adhesive properties form a watertight seal (IP 67 rated) around the PCB without any chemical reaction, ensuring that no toxic fumes are produced. It is the low injection pressure that is paramount in preventing damage to the electronics and unlike traditional potting applications, there is no need for a separate housing.
Typically, tooling costs starting around £2,500.