Light Filtering Epoxy for Surface Mount Sensors

Optical sensors are used for a wide variety of consumer, automotive and industrial applications, such as smart phones, tablets, TVs, laptop computers, self-driving cars, health monitors, and bar code scanners. For example, ambient light sensors help manage the backlighting and power consumption of Liquid Crystal Displays (LCDs) for energy efficiency and longer battery life.Infrared sensors measure invisible light to detect body heat in proximity sensors, night vision camerasand hand gesture controls. Pulse oximeters continuously monitor the oxygen level in the blood in hospital and wearable settings.

Sensors protected by miniature surface mount packages have enabled small and light weight devices for handheld and wearable applications.Although clear and light filtering epoxy encapsulants have been in volume use for decades, robust packaging for surface mount devices (SMDs) continues to be a challenge.Reflow soldering of these components to printed circuit board at 260C for lead-free applications causes extreme stress from thermal expansion and moisture absorption.


Unfortunately, the ingredients used to reduce stress for traditional semiconductors in SMDs will seriously degrade the optical properties of the encapsulant.This causes the reliability of many optical devices, such as the Moisture Sensitivity Level (MSL), to lag that of other semiconductors protected by black epoxy molding compound.

The SolEpoxyTM factory in Olean New York has supplied optical grade molding compoundsaround the world under the HYSOL and Henkel brands since the 1970s.Under the current management, there has been a renewed focus to upgrade the properties of optical encapsulants and customize them for modern surface mount applications. As a result, we have refreshed our product pipeline with a variety of new molding compounds and liquid encapsulants for sensors, LEDs and other optical components.

In addition to surface mount requirements, often it’s best for the device to only transmit selected wavelengths of light, and filter out others that cause noise and reduce effectiveness.Although special grades of light filtering glass are sometimes used for this purpose, they are expensive and not well suited to miniature devices.

One recently launched commercialized product is OP70-2, designed to block visible light for infrared devices. It features low moisture absorption and enhanced adhesion for improved MSL performance, plus custom light filtering. It features high transmittance at 840 nm and up, with a sharp cutoff at approximately 700nm, depending upon encapsulant thickness. It has passed rigorous customer qualification testing for surface mount packages. As a result of our focus on customized materials, we can adjust the light cut-off for various package thicknesses, to maintain consistent optical properties.OP70-2 is now in production and available for sampling.

In addition, we will soon be launching a similar surface mount grade molding compound for ambient light sensors.NB1111-11 features similar physical and mechanical properties, but light transmittance has been fine-tuned to mimic the response of the human eye.

We also have the capability to modify light filtering properties for various thicknesses or applications. Please contact usdirectly or through your local representative for more information.