Schott has released its AF 32 glass, which is designed for leading-edge opto-electronics applications.
AF 32 is chemically more stable and possesses a higher temperature resistance than AF 45. In addition, AF 32 has a CTE that matches silicon. This quality helps prevent warp during the manufacture of complex assemblies and during reflow, when a WLCSP imager is attached to a printed circuit board.
These properties enable manufacturers to use thinner wafer cover glasses and replace the back glasses on their packages with plastic. In addition, AF 32 glass’ CTE makes it more suitable for use in 12-inch wafer production. Schott manufactures sheets of AF 32 glass in a down-draw process, using a small tank and a narrow ribbon, greatly reducing turnaround time when changing from one thickness to another.
This method’s flexibility means that Schott can accept smaller minimum order quantities and offer its customers AF 32 glass in many thicknesses, ranging from 0.1 to 1.1 mm. This wide thickness range provides manufacturers of WLO and Micro-Electro-Mechanical Systems (MEMS) products with more design freedom, since they can secure the glass thickness they need without having to polish the glass or requalify a glass type.
A statistic process control system enforces a tight thickness tolerance in the AF 32 glass, so a Total Thickness Variation (TTV) of +/- 5 μm can be achieved right from the tank. The glass’ fire-polished surface possesses a roughness value below 1 nm RMS, ensuring that costly fine mechanical polishing is not required.
AF 32 is an aluminoborosilicate glass that is alkali-free in synthesis. This property helps ensure that a camera module’s delicate CMOS image sensors are not degraded when packaged using the WLCSP process. Easy to cut and dice, the AF 32 material helps manufactures achieve a high yield during the final dicing process for the optical assembly.