Reliable image capture: materials for CCMs

To enable lens function – either in auto- or fixed-focus lenses – an image sensor die is bonded to a substrate, which can be made from any number of materials, including FR4, ceramic or gold-plated PCBs. Because pixel counts are increasing to provide greater image resolution, die sizes are getting larger, which can lead to increased warpage. Controlling die warpage and stress with high-performance die attach materials is critical to reliable camera module operation, and it’s why Henkel’s formulations ensure success. Our portfolio of low-temperature cure, low-stress, low-outgassing die attach pastes is designed specifically for the requirements of modern camera module die bonding.

Used as an alternative to solder materials or to remove electrostatic discharge from the substrate, electrically conductive adhesives (ECAs) are found in several locations within auto-focus camera modules. ECAs are used as a solder alternative to enable electrical connection of the voice coil actuator to the spring, bond voice coil motor terminals and provide bottom-attach and side sealing stiffener for ground bonding and fixturing. Henkel’s ECAs have been optimized to deliver good electrical connections, stable electrical resistance, fast low-temperature cure, high adhesion to a variety of substrates, and no bleed-out, which all combine to deliver a robust module assembly with excellent performance.

Bonding the lens holder to the substrate requires different adhesive characteristics depending on the type of camera module being assembled. More advanced autofocus modules, however, require a different technique – particularly as pixels and lens quantity increase. For this application, active alignment is employed and requires dual-cure adhesives with UV and thermal-cure capabilities.

Bonding of the IR filter to the substrate requires a strong, yet flexible, material to accommodate fast, high adhesion curing with the ability to absorb stress. Though most substrates are ceramic, substrate materials can vary depending on manufacturing preferences and final product function. Because of this, an IR bonding material should be able to adhere to a variety of substrates. Along with excellent UV-cure characteristics, Henkel’s IR filter bonding adhesives have been designed to be compatible with both fixed- and auto-focus module substrate adhesion requirements for exceptional in-field operation.

The vision system may include a primary camera module that captures an image of an object, a light emitting element that emits light rays toward the object, and a secondary camera module that receives light rays reflected from the object. 

The bracket assembly is designed to hold these modules, and also to maintain a predetermined and fixed separation between the modules. The bracket assembly process forms a rigid, multi-piece bracket assembly to prevent bending, so as to maintain the predetermined separation.

Lens barrel attach adhesives also play a critical role in the function of the camera module. Effective bonding of the lens barrel to the lens holder requires specialized adhesives that enable low-temperature processing. Henkel’s UV lens bonding adhesives provide very rapid UV cure and handling strength, a high thixotropic index to reduce liquid migration and unwanted contamination, and the ability to enhance load-bearing and shock-absorbing characteristics. These characteristics, deliver the strength, reliability and performance required – all without high-temperature processing concerns.

Henkel offers halogen-free materials with high flexibility to support bending and folding. Low water vapor transmission rates (WVTR) provide good barrier protection. The combination of reliability and flexibility enables manufacturers to realize high-yield, cost-effective production.

To safeguard flip-chip image die applications, side capillary underfill is the material of choice to ensure bump reinforcement during reliability testing and while in use. The capability of the underfill is critical, with controlled flow essential to material containment and to avoid image sensor contamination. In addition to the flip-chip reinforcement, underfill is also used to protect the connection of the camera module to the PCB.