Die Attach Adhesive Coefficient Mismatch Mitigation in MEMS Accelerometers
Selecting low-modulus die attach adhesives with glass transition temperatures outside operating limits eliminates non-linear MEMS zero-g offset drift.
Spacer Beads
Gap Maintenance
Precision gap control utilizes spacer beads as uniform particles that establish a fixed distance between two parallel bonded surfaces. These beads are typically made of glass or plastic and are graded to a specific diameter with very tight tolerances.
Dimension Control
Dispersing a small concentration of beads into the adhesive ensures that the bondline thickness remains constant across the entire assembly. This is critical for applications like liquid crystal displays where the cell gap determines the optical performance. The beads must be strong enough to resist the pressure applied during the bonding process without crushing.
Bondline Thickness
Diameter selection depends on the required spacing which can range from a few microns to hundreds of microns. High uniformity in the bead size prevents tilt and ensures that the two surfaces stay perfectly parallel. If the beads are too sparse, the adhesive might flow unevenly and create thin spots.
Structural Support
Particles act as internal pillars that support the load and prevent the surfaces from touching. This mechanical separation protects sensitive components like microelectromechanical systems from being damaged by the package lid. Chemical compatibility between the spheres and the substrate prevents degradation of the bond over time.