In-Mold Bonding Adhesive Proves Vital to Sensor Performance

Water may be vital to human life, but it can also be detrimental to the performance of many manufactured products. One such product is the automotive sensor connector, which Pune, India-based Minda Industries Ltd. has been making for several decades. Recently, however, the company needed to address the problem of water entry causing several of its sensor connectors to fail.

Minda’s product designers researched several ways to better seal the connectors—which leaked at below 0.5 bar pressure. To that end, Minda engineers met with LORD Corp. to discuss the capabilities of the company’s in-mold bonding (IMB) adhesives. LORD offered to apply one to several connectors during molding, and then have Minda test them under high pressure to see if the adhesive provided an adequate seal.

LORD developed IMB adhesives a couple years ago to help manufacturers increase efficiency and design flexibility during molding. According to Mayuresh Patil, technical sales executive at LORD Corp., the adhesives eliminate the secondary process costs associated with pressure-sensitive-adhesive tapes and structural adhesives. They also enable engineers to more easily design curved, thin and lightweight devices.

IMB adhesives structurally bond a plastic or metal substrate to a liquid thermoplastic or silicone rubber during injection or compression molding. Equally important, they create a strong seal that resists liquid or gas ingress and egress.

In the Minda test case, an IMB adhesive was applied to copper-alloy terminal pins, and nylon was poured onto the pins during injection molding. Each connector was then subjected to high positive pressure (up to 3 bar) for a specific time. Test results showed that no treated connector leaked, and the adhesive withstood thermal cycling better than the old sealant.

Minda has since begun using the adhesive on various connectors in production, with no customer complaints about sensor failure due to water entry. Patil says Minda especially likes the adhesives because they require no special surface preparation or atmosphere conditions, and are environmentally friendly.

Eight types of IMB adhesives are available (1010, 1020, 1040, 2000, 2010, 3010, 3020 and 3030), with viscosities from 100 to 7,000 centipoise. They are clear, clear to yellow, white or milky in color. The 1040 adhesive provides enhanced humidity and high-temperature performance.

Any of the adhesives can be easily applied to a substrate by brushing or spraying, or dipping to achieve a specific desired film thickness. The substrate is inserted into a mold that gets filled. Finished bonded parts are then removed from the mold in the standard manner.

Compatible substrates include aluminum, anodized aluminum, glass, steel, stainless steel, polycarbonate, select polyamides, nylon and magnesium. Acceptable thermoplastic molding materials are polycarbonate, ABS-polycarbonate, nylon, PBT and select elastomers. Current applications include consumer electronics (wearables, cell phones, cases), automotive components (ignition coils, injectors, pumps, solenoids, connectors) and medical devices.

LORD Corp. is a diversified technology and manufacturing company that develops adhesives, coatings, motion management devices and sensing technologies. It works closely with many customers in the oil and gas, aerospace, defense and automotive industries. For more information on in-mold bonding adhesives, call 877-275-5673 or visit www.lord.com/imb.

Jim was a senior editor of ASSEMBLY and has more than 30 years of editorial experience. Before joining ASSEMBLY, Camillo was the editor of PM Engineer, Association for Facilities Engineering Journal and Milling Journal. Jim has an English degree from DePaul University.

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