Manufacturers employ various techniques to overmold, seal, and safeguard cables and electrical connectors from moisture, dust, debris, vibration, and strain. The two primary overmolding techniques are "low-pressure" and "high-pressure." Each method has its advantages and disadvantages, but the choice of overmolding technique depends on the specific type of electrical assembly and its intended application.
Both high-pressure and low-pressure overmolding techniques follow a similar process. It begins with melting adhesive thermoplastic polyamide materials in a large hopper. Next, the cable and connector components are placed in an enclosed mold. Finally, the molten material is injected into the mold to encapsulate the cable and connector, resulting in a unified product.
High-pressure overmolding, as the name suggests, involves injecting molten material into the mold at a higher temperature (185-300+°C) and pressure (around 25,000 PSI) compared to low-pressure overmolding. The higher pressure results in a faster injection time, allowing 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).
- PCB housings
- Plastic parts
- Medical devices
- Auto dashboards
- Fast cycle time
- Greater efficiency
- Greater durability
- Ideal for high-volume orders
- 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 uses a lower melt temperature (180-220°C) and less pressure (around 100 PSI) when injecting molten material into a mold cavity. Low-pressure overmolding is particularly suited for delicate electrical equipment like sensors and PCBs, which are prone to damage when exposed to higher pressure and temperature. One distinctive feature of low-pressure overmolding is its use of low-viscosity polyamide resins, which have a consistency similar to syrup (2,000–10,000 mPa•s (cP)). This low-viscosity material can effectively fill intricate and hard-to-reach cavities without the need for additional pressure. As a result, manufacturers can mold thinner walls with minimal freeze-off.
- PCBs
- Sensors
- Switches
- Batteries
- Gentle on delicate electronics
- Greater uniformity
- Excellent precision for complex designs
- Better aesthetics
- Eliminates front-flow hesitation
- Slower cycle time (relative to high-pressure molding)
- Less durable (compared to high-pressure molding)
- Lower cost of ownership
- Less material consumption
- Reduced 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.
