Photodiodes Designed to Detect Rain & Handle Moisture

Osram Opto Semiconductors has developed what they say is the world’s first surface-mount technology (SMT) package for photodiode chips.

Osram Opto Semiconductors (osram-os.com) has developed what they say is the world’s first surface-mount technology (SMT) package for photodiode chips which not only allow the SFH 2200 A01 and the SFH FA A01 (this latter one has a daylight filter) to be mounted behind the windshield glass to perform as rain sensors (when a raindrop hits the windshield, the diodes detect a change in the incidence of light, and the number of drops affects the overall amount of light detected, thereby causing the wipers to work at varying speeds), but which facilitate manufacturing, as they’ve improved the moisture sensitivity level in the chips—which has nothing to do with rain, but with soldering.

That is, the amount of moisture in a component can have deleterious effects on its solderability. These new photodiodes can be soldered without damage for one year after the dry packaging is opened to the air—assuming, of course, that the components are stored at a temperature of ≤ 30°C and 60 percent humidity.

Rajeev Thakur, regional marketing manager at Osram Opto Semiconductors, explains how this works: “By using encapsulation material containing silicone, we’ve provided a way for moisture and gases to escape more quickly during soldering. The combination of silicone and the stability of the plastic package of the component ensures that the photodiodes are particularly robust.”

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Also notable: the photodiode package is small, measuring just 4.0 x 5.1 x 0.85 mm.