Low Pressure Overmolding

The excellent technology for effective protection of electrical and electronic devices.

[written by Marco Castro]

What’s about?

Low-pressure overmolding technology is based on the use of polyamide resins (known as hotmelt resins), which are injected at low pressure into suitable moulds in order to create effective protection for an object, using specific machinery.
It is the ideal solution for the protection of electrical and electronic devices.
For this reason it is mainly referred to as 'overmolding' and not as molding.

The reason to use this technology is to be able to protect an electronic or electrical device from heat, humidity, dust, vibrations and shocks.
These devices could be protected using injections of traditional thermoplastic materials (such as PVC or standard polyamides), but the high injection pressures required to process these materials would damage the components that have to be protected.

Key aspects of the technology:

- Raw materials:
differ from traditional thermoplastics by two main characteristics: viscosity and adhesion. The first offers the possibility of injecting the materials at low pressure (2-40 Bar): the equipment has got an ordinary gear pump to inject the melted material (typically 210°C); the second allows the components to be perfectly sealed, guaranteeing the required protection.

- Equipments:
specifically studied and designed for the injection of hotmelt materials. The equipments guarantee perfect process parameters’ control such as temperature, time and speed.
Failures during the control of one of these parameters will result in manufacturing defects, long cycle times and generally poor quality of the finished product.

- Planning and design:
Only who have a deep knowledge of the technology and resins is able to meet the technical requirements and guarantee the right protection, resistance, dimensions and shape for the products

- moulds:
fix the shape of the finished product. The quality of construction and attention to detail are the results of the use of hotmelt resins are the necessary elements for reaching a correct work cycle and the success of the project.

Advantages and applications

Overmolding benefits:

  •    Low pressure injection process
  •    Absence of solvents or other toxic substances
  •    Short working cycles and possibility of getting a finished part immediately available without further modifications
  •    Personalization of the product by applying logos, identifiers and customized shapes
  •    Use of compact equipment with modular and configurable systems.

The Overmolding solution can be used in different fields such as automotive, microelectronics, sensors, medical and, in general, where it is necessary to guarantee the protection of a device in an efficient and continuous manner.

It is a steady technology in the production of moulded connectors and for the protection of electronic circuits. In this case it is used to replace epoxy resins which have very long cycle times and which expose workers to the inhalation of toxic substances.

The diagram below shows the difference between hotmelt resins and high-pressure resins in terms of temperature and pressure.

formerly published on 08/02/2021

Useful Tips...

This technology is often considered as a sort of simplification of the traditional moulding. This is why we are not used to pay attention to important details such as the use of suitable techniques and materials for the moulds or special shapes, etc...
Sometimes it is necessary to adapt or re-design the shape and the dimensions of the final products in order to meet the application requirements.

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