Manufacturers use a few different techniques to overmold, seal and protect cables and electrical connectors from moisture, dust, debris, vibration and strain. The two most popular overmolding techniques are “low-pressure” and “high-pressure.” Each technique has its pros and cons, but ultimately, the method a manufacturer chooses to use for overmolding depends on the type of electrical assembly and application.
The Overmolding Process
High- and low-pressure overmolding techniques follow a similar process, which involves melting adhesive thermoplastic polyamide materials in a large hopper, placing the cable and connector components in an enclosed mold, and injecting the mold with the molten material to encapsulate the cable and connector, resulting in one unified product.
High-Pressure Overmolding
As the name suggests, high-pressure overmolding injects molten material into the mold at a higher temperature (185-300+°C), and pressure (around 25,000 PSI) compared to low-pressure overmolding. Higher pressure equates to faster injection time or time needed to fill the mold cavity, which allows manufacturers to produce more overmolded cables in less time. The material viscosity of high-pressure overmolding is comparable to taffy (around 5 grams over 10 minutes).
Common Applications:
- PCB housings
- Plastic parts
- Medical Devices
- Auto Dashboards
Pros:
- Fast cycle time
- Greater efficiency
- Greater durability
- Ideal for high-volume orders
Cons:
- Higher melt temperature and pressure can damage delicate electrical components.
- Material viscosity can shear off components.
- Faster fill-rate can produce flaws or “molded-in stresses,” uniformity issues, flow-front hesitation, and other issues that can impact quality, performance and aesthetics.
Low-Pressure Overmolding
Low-pressure overmolding uses a lower melt temperature (180-220°C) and less pressure (around 100 PSI) when injecting molten material into a mold cavity. These less abrasive manufacturing elements make low-pressure overmolding ideal for delicate electrical equipment, such as sensors and PCBs, which can easily become damaged if exposed to a higher pressure and temperature. The other quality that sets low-pressure overmolding apart from other techniques, including high-pressure overmolding, is its use of low-viscosity polyamide resins, which resemble the consistency of syrup (2,000–10,000 mPa•s (cP)). This low-viscosity material can easily fill intricate, hard-to-reach cavities without requiring additional pressure, allowing manufacturers to mold thinner walls with less freeze-off.
Common Applications:
- PCBs
- Sensors
- Switches
- Batteries
Pros:
- Gentle on delicate electronics
- Greater uniformity
- Excellent precision for complex designs
- Better aesthetics
- Eliminates front-flow hesitation
Cons:
- Slower cycle time (relative to high-pressure molding)
- Less durable (compared to high-pressure molding)
Overall Benefits of Pressure Molding
- Lower cost of ownership
- Less material consumption
- Less equipment and operations footprint
- Lower cycle time per part
- Fewer manufacturing steps
- More environmentally friendly
- Higher quality outcomes
- Excellent resistance and protection
In either case, injection molding is the superior manufacturing technique for overmolding electrical cables and connectors compared to other approaches, such as potting, which requires more resources, time, equipment and steps to produce a less-superior product.
To learn more about overmolding electronics, download our free guide.
