CMOS image sensors are essential components in modern vehicles and are installed, for example, in Lidar and driver monitoring systems. They must be sealed to keep out dust and moisture and maintain their safety functions over their entire service life.
Glass filters can be bonded to the semiconductor chip using Delo Dualbond EG6290. The electronics-specified adhesive can be dispensed in narrow, high bondlines, can compensate for temperature-dependent pressure changes, and meets routine automotive standards.
The new adhesive was designed for the glass-on-die assembly method. The glass filter is fixed directly onto the chip, as is typical with iBGA image sensor packaging.
Compared to previous products, Delo Dualbond is said to have a higher Young's modulus of 2,350 MPa and higher adhesion value. Due to a glass transition temperature (Tg) of over +130 °C, the adhesive exhibits mechanically consistent behaviour—even at high application temperatures, for example, during the moulding process—and can compensate for temperature-dependent pressure changes. Delo Dualbond EG6290 thus fulfils the requirements of the AEC-Q100 Grade 2 automotive industry standard.
The adhesive is applied via needle dispensing. Thanks to its high thixotropy index, narrow and high bondlines can be precisely dispensed, onto which the glass filter is then joined.
Curing takes place in two successive process steps: First, the adhesive is exposed to light with a wavelength of 365 or 400 nm. Then, as a result, the glass filter is fixed within a few seconds. The adhesive typically cures in 15 minutes at +130 °C. Due to the rapid curing reaction, the matrix in the adhesive builds up quickly, which ensures the image sensor package is reliably sealed.
According to Delo, both the dual curing process and the comparatively low curing temperature help to minimise the pressure that usually occurs when bonding glass filters.
