Low pressure Molding, What Is It, How It’s Used and Where, the Process

 

Low pressure molding is a technique we all see and encounter in our everyday lives, even though you may not realize it, low pressure molding is integral in many of the appliances and equipment you may use daily. It silently goes about its business and you probably don’t give it a second thought.

Here at QL-Custom we have many years of experience with low pressure molding, so we thought we’d share some of the main points about this process with you in this article.

Here’s a quick take away answer for you, then we’ll dive deeper into the process and benefits of low pressure molding, not only for applications but for the environment too.

 

So What is Low Pressure Molding? Low Pressure Molding is a technique for protecting and encapsulating components prone to damage, moisture, or other external influences. Typical in applications such as wiring and printed circuit boards. Using materials known as hot-melts, polymers are used to seal around components using specialist machinery.

 

Dimer acid based Polyamide materials often referred to as ‘hot-melts’, are thermoplastics that, when heated to specific temperatures become pliable and malleable for use around precious connectors and connections.

 

 

Why it’s called Low Pressure Molding

 

Low pressure molding, (or LPM) in particular, is as the name suggests, the use of lower pressure processes and techniques used where components may suffer from the normal pressure or extreme heat otherwise used in more industry standard pressure molding applications.

To reiterate, there are two main reasons an application may require the use of Low Pressure Molding.

 

Malleability

One major factor is the need for the applied thermoplastics to be more viscose. Viscosity allows the injected material to be applied to much small or complex spaces and cavities. To apply at low pressure often a manual gear pump process is used, this provides sufficient pressure to drive the viscose material between components.

This helps to prevent fragile components from becoming dislodged or broken and provides greater protection and stability to otherwise unprotected electronics.

The viscosity is measured in what is known as centipoise – a specific unit of measurement, and at around 410F (210C) this forms the consistency of ‘Pancake Syrup’ which is sufficient and safe for low pressure application.

 

Adhesiveness

Generally speaking, Polyamide materials are considered to be high-performance hot-melt. Polyamide has an adhesive quality that accompanies it and this is what helps to seal in components.

 

The Low Pressure Molding Application Process

 

If a PCB board or other circuitry is to be Low Pressure Molded, then after the PCB has been manufactured, it will then move on to the next phase which is Low Pressure Molding.

Low Pressure Mold starts out in small pellet form, these pellets are measured out into the correct quantity/weight required and fed into a specialist LPM machine – which also houses the mold template to be filled. The finished PCB is placed into the machine – or a cold-mold set is applied as an initial barrier to any heat from the pressured injection. Then it’s ready for applying the main thermoplastics layer. Once heated to 410F, the Polyamide is then injected – either manually or mechanically using low pressure methods, usually around 50 to 200 PSI.

The flow is maintained and regulated, it will surround components and even begin drying and sealing on contact. The amount injected is measured and directed exactly to fill all the necessary components and leave a finished surface. High-speed advances mean this process typically only takes a few seconds per application, with the completed injection, drying and finishing time extending up to about 1 minute. Resulting in viability for mass production.

 

Injection To Combat shrinkage

 

Once injected, the Polyamide will typically reduce, or shrink in size during the drying phase. In order to compensate for this, the unit is continuously injected in order to maintain pressure against the units and fill any void left by shrinkage. This process is continued until the Polyamide transforms from a liquid to a solid. i.e. heated to cooled. meanwhile, the cold-mold application will absorb any undue pressure and heat that may occur during the process.

 

This technique has been proven to protect fragile components while not rupturing electronics or solder joints and does not impede the performance of the unit.

 

Why We Use Low Pressure Molding

 

Since the 1970s when low pressure molding was developed in Europe, the use has spread to most industrial and consumer areas. Initially developed for the automotive industry to replace heavier alternatives such as Potting process which was also more toxic and to provide an efficient, sealed and protective environment for components that otherwise would suffer from undue strain and breakage.

 

Techniques have since improved still further, providing greater protection and being able to cover more complex systems. So Low Pressure Molding has extended to cover not only industrial and commercial uses but also to Military and Aerospace applications, where more extreme equipment and electronics require more robust solutions.

 

Add to this that low pressure molding is a less toxic environmentally friendly solution and you can see why its use has extended to most areas of circuitry protection.

Here’s a list of typical applications for Low Pressure Molding

1. Military
2. Aerospace
3. Automotive
4. Static Industrial Equipment
5. Mobile Industrial Equipment
6. Construction Equipment
7. Consumer Electronics
8. Motors and Control Boards
9. Submersible Equipment
10. Sensors
11. Lighting Setups
12. Mobile Electronics such as USB drives and Remote controls
13. Almost all forms of manufactured wiring

 

In many applications the molding itself has developed to become an essential part of the unit itself, for example, the molding used in USB Pen drives and Remote Car Door Locks often form part of – or the complete outer casing of the product, or in some instances dictates the shape of the outer casing.

 

The Benefits of Low Pressure Molding

 

Lightweight Material

As opposed to heavier more cumbersome techniques, hot-melts provide a more weight efficient final product which is ideal for most applications

 

Watertight Finish

Units that could otherwise be prone to water damage can now be hermetically sealed from outside, allowing sometimes deepwater equipment to remain safe and fully functioning.

 

Multiple Surface Adhesion

Low pressure molding, along with the cold-mold enables a multitude of different materials to be applied with adhesive in order to help stabilize and secure components in place.

 

Shock Resistant

PCBs and other components used in high impact environments can now be afforded greater protection from impact and other damage suffered whilst in use.

 

Chemical Resistant

Components coming into contact with externally non-acidic applied chemicals can now be protected without harm occurring to internal circuitry

 

Compact

The use of low pressure seals provides internal protection, requiring less outer protective needs. This leads to a more compact and space saving design, without comprising on stability and protection.

 

Aesthetic

This form of sealing and molding method provides much greater improvements over form and design than previous methods of protection.

 

Compliance

All Thermoplastics and Polyamide materials conform to ISO approved standards for health and safety in all applications.

 

 

Environmental Benefits to Low Pressure Molding

 

Inf fact Pressure Molding as a whole has many environmental benefits over and above previous practices and in some cases prolongs benefits that cancel out the use of this process. Here are the main environmental benefits of Pressure Molding.

 

Natural Products

All the ingredients used in Pressure Molding are natural materials.

 

Recyclable

Any excess material produced by Pressure Molding is fully recyclable. The material can be reclaimed and re-used numerous times. This means Pressure Molding is a Zero Waste solution

 

Hazardous Fume Free

The process of Pressure Molding does not produce any hazardous materials, either airborne or in liquid or solid form.

 

Product Life Extension

Products which otherwise would have been given a ‘Use by’ date can now be stored and used after a greater period of time.

 

Fewer Product Breakages

 

Now that products are more robust, the chance of breakages or faults is fewer, meaning fewer PCBs or circuits are discarded and/or require replacing.

Conclusion

 

As mentioned initially, low pressure molded practices have become so commonplace that we barely notice them around us every day, even though we probably come across them several times a day in our work and home life.

 

Typical consumer and small applications include products like cables or cable junctions where they’re used to strengthen and protect cable ends. Products you may pick up and use daily like your car door remote or even your TV remote probably also contain Low Pressure Molding products to help prolong their life and any impacts they may come in contact with.

 

If you have an application that you’re considering the need for Low Pressure Molding, or even if you want to know if your product is suitable – or ready for this process, then it’s always a good idea to find out more information.

 

If you’d like to discuss your particular project, whether it’s for a handful of prototype units, or for a run of thousands of units, thencome and talk to us here at LPM  where one of our experienced specialist team members can assist with your inquiry and walk you through any necessary processes.