According to the FLEXcon (Spencer,
MA, U.S.), SWITCHmark LX 3-1-2 is specifically engineered for bonding
silicone rubber keypads to membrane switch applications, making it ideal
for a broad range of demanding appliance applications.
According to Christopher J. Drury, market development leader
for FLEXcon's Performance Products Business Team, the main feature SWITCHmark
LX 3-1-2 offers designers is lower total applied cost for switches utilizing
silicone elastomer keypad materials. "This is accomplished by providing switch
manufacturers with an adhesive product that eliminates process delays and
challenges typically associated with silicone adhesive die cutting and silicone
keypad bonding," he
FLEXcon's traditional SWITCHmark line is made up of high-performance
laminating adhesives, spacer components, and backer materials.
Pictured is the company's new product line, the SWITCHmark
LX 3-1-2, which utilizes an acrylic adhesive engineered
for demanding membrane switch applications.
One time-saving feature, Mr. Drury says, is the 0.003-in of moderate tack silicone adhesive that has been applied to one side of the product's 0.001-in polyester carrier. The high-performance, moderate-tack, silicone pressure-sensitive adhesive reportedly enables continuous processing and assembly of switches by providing an immediate bond to silicone rubber keypads.
Mr. Drury explains: "Silicone adhesives traditionally have little to no tack. As a result, membrane switch manufacturers using other silicone adhesives must hold keypads in a queue, commonly up to 24 hours, after the adhesive lamination has been made. This 'holding' period gives the other silicone adhesives time to build a bond prior to additional processing and assembly. The tack in concert with the adhesion properties of this silicone adhesive allows for instant bonding without the need for primers, which are required with some other adhesive systems."
SWITCHmark LX 3-1-2 also utilizes 0.002-in of a high-performance acrylic adhesive on the other side of the polyester carrier. This acrylic adhesive, Mr. Drury notes, was engineered specifically for demanding membrane switch applications. The adhesive has both UL 746C (polymeric adhesive for use in electrical equipment) and UL 969 (label and marking systems standard) recognition.
"This acrylic has superior shear and adhesion properties for superior holding power and bond under stress (such as high heat, humidity, or temperature cycling), and has been designed with low tack to provide a window of reposition-ability through the switch assembly process," Mr. Drury says.
The SWITCHmark LX 3-1-2 was also designed with the die cutting process in mind. It is manufactured with heavy lay-flat liners on both sides of the construction (78# on the silicone adhesive side, 80# striped liner on the acrylic adhesive side), resulting in a lay-flat sheet. This, Mr. Drury says, eliminates the handling and die-cutting challenges associated with products supplied in roll form. "Our design allows switch manufacturers to handle and die cut the product with ease," he notes.
Overall, Mr. Drury believes the improved economics of the new bonding material will enable designers to consider using silicone elastomer keypads in a broader range of appliance applications, while retaining the confidence in product performance. Possible applications include security system controls, point-of-sale devices, and hand-held industrial and consumer devices such as remote controls and barcode scanners for inventory tracking.