Over-Molding Silicone to Glass

A Casco Bay Molding customer initiated an experimental project for over-molding a Silicone well-structure onto a glass slide.  We worked with our customer to define their part design.

Over-molded Silicone Wells onto Glass Slide Design Goals:

  • Do not break glass slides
  • Achieve a water tight bond between glass slide and LSR
  • Create a well defined silicone grid structure
  • Develop a simple/cost effective manufacturing process
  • Validation to be completed by customer lab testing

After consulting with Mr. George Kipe of Kipe Molds, it was decided to develop a special cavity pocket for the glass slide to insure even pressure across its entire surface. We designed the mold’s core and cavity set around the “glass slide pocket.”  The mold was tested and venting gating adjustments were made to optimize mold filling. Initially the bond was not to our liking, so we experimented with a number of LSRs (liquid silicone rubbers) to find the optimum formulation. We tested “self-bonding LSR” and standard LSRs, eventually settling on a silicone that bonded well to the glass without the need for a priming agent.

Other Plastic and Metals over molding projects and experimentation have involved Plasma coating, Corana treatment, UV treatments and multiple combinations of Silicone primers and standard & self bonding silicone.