An injection-molded and metalized plastic part features 3-D connections with multiple points of contact
The OmniPod diabetes management device's chassis was injection molded and then selectively plated.
With its insulin-delivery device dubbed the OmniPod, Insulet Corp. (Bedford, MA; www.myomnipod.com) strives to improve the lives of patients suffering from Type I diabetes by providing a convenient, unobtrusive means of managing their condition. Although it functions similarly to a conventional insulin pump, the OmniPod consists of a handheld personal diabetes manager that wirelessly transmits instructions to a disposable, skin-mounted, tubeless pump that is replaced every three days. The device performs numerous tasks that include automatically inserting a cannula into a patient and pumping and metering designated doses of insulin.
Desiring to further enhance the product, Insulet embarked upon a redesign that focused on the chassis, which serves as the electrical and mechanical hub of the device. The company sought enthusiastic new partners capable of pushing the envelope; it found them in Phillips Plastics Corp. (Hudson, WI; www.phillipsplastics.com) and SelectConnect Technologies (Palatine, IL;
The chassis design called for the use of 3-D molded interconnect device technology to create a plastic injection-molded part that was then metalized to form 3-D PCB connections with multiple points of contact. “From an injection molding standpoint, just the multishot nature of this component and the complex geometry made it a very difficult part to mold, and then adding a platable aspect added another layer of complexity,” recalls David Clare, senior project manager
Phillips, an injection molding company, molded a clear, nonplatable polycarbonate (PC) in the first shot. It then selectively molded the polymer with a green PC-ABS material that was modified with an additive to make it platable. The second shot was especially difficult, Clare notes, because it required upwards of 14 gate locations to ensure separation of the part’s 12 discrete circuits, which each perform different electrical functions.
Once injection molded, the part was passed on to SelectConnect for treatment with its patented plating process in order to make the PC-ABS conductive. Following exposure to chemical baths, the part underwent an activation process to prepare the polymer for plating. Next, a 250-µin. layer of electroless copper was deposited onto the PC-ABS as a base layer followed by the addition of a 50-µin. layer of electroless nickel on top of the copper. The nickel lends oxidation resistance to the copper prior to final assembly.
“The benefit to our plating technology is that you can have your circuit traces now directly on a plastic component,” says Doug Gries, vice president of business development, SelectConnect. “Rather than having a separate circuit board or flex circuit, circuitry is now integrated within the plastic part.” This operation, Gries adds, allows for parts consolidation, miniaturization, and potential reduction of weight, assembly operations, and overall system cost.
Although SelectConnect has 50 years of experience plating metal, the OmniPod chassis represented the company’s first foray into plating plastics. “Plating on plastics has been done for a long time,” Gries states, “but this specific process of selectively plating to create discrete circuitry on plastic components is relatively new.”
For a Web-exclusive article on SelectConnect's innovative laser-based plating technology for plastic injection-molded parts, go to http://www.qmed.com/mpmn/article/17951/laser-based-process-yields-3-d-circuitry-molded-plastic-parts
Published in MPMN, April 2010, Volume 26, No. 3
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