Among all the Device Bonding applications, the assembly of Infrared Focal Plane Array (IRFPA) counts within the most challenging. The infrared is a type of “light” (radiation of heat energy, related to the temperature of objects) that is outside the range of the human eye. IRFPA is similar to the imaging chip in a digital camera, except it is sensitive to infrared instead of visible light. Whereas your digital camera uses a Silicon sensor, infrared sensors are made of different materials, i.e. HgCdTe, InSb, InGaAs, etc.; the sensor chip in then bonded onto the Read-Out Integrated Circuit (ROIC) using the Flip Chip Technique. IRFPA is not an ordinary “Flip-Chip” application. Pixel and bump size is smaller, respectively 8µm and 4µm for the most advance devices. Hybridizer is required to perform sub-micron bump-to-bump alignment in X, Y, and θ, maintain die parallelism and resist to lateral slip as bond force increases.

LDP150 Inside View

Since 1981, SET made a specialty of these High Force and High Accuracy Device Bonders providing safe handling for large fragile die. With the increasing number of pixels, Higher Force (>10kN) is required leading to a two-stage bond (precision tack, then high force press) or new techniques to reduce force-per-bump.  The LDP150, Large Device Bonding Press, has been especially designed for bonding large detector Arrays (light or radiation detectors) with size ranging from 50 to 150 mm. The equipment uses compression processes at room temperature but can also be equipped with heating chuck for thermo-compression bonding.

The components are previously aligned and pre-bonded using High Accuracy Device Bonder such as the SET FC150 or FC300. The devices are then pressed together at room temperature while the initial alignment and parallelism accuracies are preserved.

The LDP150 is able to apply force up to 100kN while the self leveling sphere, moving on the air bearing and locked by vacuum, preserves the initial gap parallelism of the component stack. The granite base and rigid stiff steel structure associated to an accurate bond profile maintain the initial high accuracy of the assembly and ensure bond join quality.


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