Low pressure thermoplastic molding a flexible fit for device encapsulation

Sensitive electronic components such as battery packs, micro-switches, solenoids, sensors, connectors and wire harnesses employed in the automotive and electronics sectors more often than not need to be well protected from dust, moisture and grime. Conventionally, potting or conformal coating (brushing, dipping or spraying) processes employing thermoset resin have been employed to encapsulate such electronic components but in recent years, a thermoplastic option has been making strides in the market on account of its efficiency, cleanliness and design flexibility.

Pioneered by Taiwanese company LPMS International (Taizhong City), low pressure molding is said to be a single-step process to quickly encapsulate, seal and protect electronics. Using a simple mold set allows for the process to use much less material than the traditional potting process, while requiring no housing. Further, part numbers and logos can easily be incorporated into the mold set for added benefits.

LPMS initially developed and started manufacturing machinery for the process in 2004 and currently offers various models including vertical, horizontal and multi-shot injection units. The injection unit itself is comprised of a melting pot for the thermoplastic pellets (typically a polyamide hot melt resin grade such as Technomelt from Henkel (Dusseldorf, Germany)), a gear pump to transfer the resin melt into the tool under low pressure, and a bypass valve for pressure regulation.

"Viscosity can be regulated by the heating temperature employed in the melting pot," says Grant Liu, Founder & President of LPMS. Further, while polyamide suffices 99% of the time, "there may be some cases where adhesion to metal or other plastics requires the use of a polyolefin-based material," says Liu. "Shot sizes may vary from several grams up to 300 grams, with cycle times of 2-3 seconds up to 2 minutes.

"The low pressure molding process can be used to encapsulate complex components because we can design tooling to exact customer requirements," says Liu. "Whether it's an LED or a microswitch, we can certainly overmold in the most efficient way."

LPMS itself is comprised of four business units. One designs and build machines, 30-40 per month at last count, for sale to processors. The company also has its own tooling business that will turn out 1500 tools this year according to Liu. The third business unit distributes the resins required for the process. Finally, LPMS also offers molding services to those not yet ready to take the plunge. "We have almost 40 machines at out site in Dongguan, China, to provide molding services," says Liu.

Low pressure molding comes to the US

In June this year, LPMS announced the formation of LPMS USA. Located in Lake Zurich, IL, the US affiliate is a full-service low pressure molding solution provider offering in-house machines, mold fabrication services as well as contract manufacturing. Heading up LPMS USA is Michael Cooper, whose interest in LPMS was to gain access to the latest in low pressure molding technology, and to fill a need in the US market for encapsulating electronic components.

Cooper's long-time focus has been offering a high level of service to customers, while providing the latest in materials and delivery systems. He has been in the adhesive industry for 35 years, according to Kevin Ross, sales consultant for LPMS. Cooper has also been a distributor for LPMS since 2012.

Low-pressure molding is a very large "niche" market, Ross explained to PlasticsToday. "It is ideal for very specific products, but it's almost one of the best kept secrets. It's one of the most in-demand processes for encapsulation in the electronics and electrical industries because of the low temperatures and pressures, which doesn't compromise the electronics like conventional injection molding would. While we can't replace all potting applications, only about 4-5% of the projects that we come across aren't a good fit due to sizing or parts that have intricate detail work, which wouldn't be a good fit. But for the remaining 95% it's a fit."

LPMS USA benefits from LPMS International's long history of service and innovative technology. They have over 25 custom machine options - from large to small, the ability to fabricate a mold within 10 business days, and a dedicated engineering team to assist with design modifications and recommendations.

Ross noted that LPMS USA has signed an agreement with Henkel to sell Technomelt and Macromelt adhesives. "It made sense for us to align ourselves with the Henkel brand and reputation," he said. "With limited exposure [to date] we've had phenomenal response."

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