Deformable Conductive Bondline Spacers – Silver-Coated PMMA Microspheres

What are bondline spacers?

Microspheres as Bond Line Spacer

Image courtesy of Nikkei Business Publications

Microspheres are widely used as bond line spacers because today’s technological advancements are demanding tighter and tighter tolerances.  Assembly of many instruments, especially in electronics, optics, biotechnology, calibration, and medical devices, requires holding precise spacing between parts.

Depending on the requirements of the application, a rigid non-flexible bond line may be required. In these circumstances a non-deformable rigid materials like spacer grade soda lime glass microspheres, spacer grade borosilicate glass microspheres, or monodisperse silica microspheres are used to hold the exact dimensions of the bond.

What are conductive bondline spacers?

Conductive Bondline Spacer - Silver-Coated Silica Spheres

Conductive Bondline Spacer – Silver-Coated Silica Spheres (Cospheric LLC Product Line: SiO2MS-Ag)

Electrically conductive microspheres are often used as a conductive spacer to create precise bondlines that also provide electrical conductivity.  Conductive silver-coated microspheres are widely used in many industries due to the combined benefit of precise dimensions and electrically-conductive properties.

Typically at 20% loading micropspheres in an epoxy can create effective shielding against electromagnetic interference (EMI). Conductive silver coated microspheres are commercially available in a large selection of particle sizes and densities from Cospheric LLC.

What are deformable bondline spacers?

PMMA Microspheres - Technical Specifications

PMMA Microspheres – Technical Specifications (Cospheric LLC Product Line: PMMA)

For some applications t may be advantageous to have a bondline that is more flexible and deformable.  In these situations polymeric spacer material such as PMMA microspheres (also known as poly(methyl methacrylate) or acrylic microspheres) is used.

Deformable and conductive bondline spacers are ideal when some deflection of the particles is preferred while maintaining conductivity and compliance.

What are deformable conductive bondline spacers?

Deformable Bondline Spacers - Conductive Silver-Coated Poly(Methyl Methacrylate) PMMA Microspheres

Conductive Silver-Coated Poly(Methyl Methacrylate) PMMA Microspheres – Deformable Polymer Bondline Spacers (Cospheric LLC Product Line: PMMA-Ag)

Poly(methyl methacrylate), also known as PMMA or acrylic, micropshere cores can be combined with a conductive silver coating to create deformable conductive bondline spacers. This unique bondline spacer offers benefits for Ansiotropic Conductive Film (ACF) applications, creating conductivity in one direction.

The combination of the thick coating of the silver and the bonding to the compliant deformable polymer sphere provides a durable solution.

Unlike conductive silver coated glass microspheres, which work well for increasing the conductivity of bond lines but lack the capability to deform when compressed, Silver Coated PMMA Microspheres offer the low weight deformable PMMA cores and 250nm thick silver coating for high conductivity, while providing increased conductive contact between the surfaces of the bond line.

These spheres are perfect for producing anisotropic (only conductive in one direction) conductive bond lines. Actual bond line thickness achieved will be a function of the assembly pressure and the size of spheres selected. In addition to being highly conductive, these silver coated PMMA microspheres are bio-compatible and suitable for biomedical applications.