Chip on Board Assembly | Optoelectronics & microelectronics

Chip on Board Assembly is the process whereby a bare semiconductor die is mounted on a substrate using conductive or non-conductive epoxies. Die are electrically connected using Au ball bonding or Al Wedge Bonding. The die is then protected using a glob top or Dam/Fill encapsulation process.

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Wire Bonding Section

Wire bonding is the main method of making interconnections between a semiconductor die and a package or substrate.wired-optocap

Optocap works closely with our customers at the package design stage to ensure that design for manufacturing techniques are applied and wire bond design rules, where possible, are adhered to. This co-design activity is crucial in the development a high yield, fully automated and fully optimized wire bond process.

By controlling and optimizing key wire bond process and material parameters such as ultrasonic energies and wire specification a robust and reliable wire bond processes can be developed.

Optocap also offers wire pull and ball shear test data to enable qualification of the wire bond process.

Optocap’s expertise and capability in wire bonding will reduce risk and reduce time to market for your wire bonding requirements as well as providing a cost-effective manufacturing option.

Encapsulation Section

Encapsulation is the process to protect die from damage after die attach and wire bond. There are two main types of encapsulation: Glob Top and Dam and Fill.

Glob top is a process whereby a low viscosity encapsulant is dispensed on top of the die. The encapsulant flows and conforms to the shape of the die without damaging wire bonds. However, the encapsulant can flow beyond the desired area and into adjacent areas. In many applications, such as the encapsulation of MEMS devices and Concentrated Photovoltaic devices,  a controlled partial encapsulation of certain selected regions, for example wire bonds, is required, but ensuring that the active surface of the device is free from encapsulant.

The tight control for partial encapsulation requires selection of a suitable encapsulant and development of an appropriate dispense process.

Dam and Fill encapsulant uses a dam around the die area to control the encapsulant flow within a contained area. This process can result in much flatter encapsulation profile. It requires dispensing of two or more encapsulant materials in the same dispense program during an automated process.

Variations of the above processes can be used to fully encapsulate Open-Cavity Plastic Packages. Using a subsequent flattening technique on the encapsulant the package can meet the original JEDEC form-factor standards and provide test socket compatibility.

Optocap also has experience with a range of optically clear encapsulant and silicones for protecting devices such as LEDS and Photovoltaic’s. Optocap also supports customers with the design and procurement of frames suitable for containing the encapsulant material.

Hermetic Sealing

Hermetic Sealing

Optocap provides hermetic sealing of various metal package configurations including TO-can style package and Butterfly packages.
Parallel resistance welding is used for rectangular or square packages. Projection welding is used for TO-can devices.
Prior to sealing parts they are put through a Vacuum bake-out process to remove moisture and other residues from the component surfaces. Devices can be hermetically sealed in a wide variety of inert gas atmospheres including N2, Ar, O2, depending on the customers exact requirements.
Fine and Gross leak tests are carried out to MIL-STD-883. Optocap have achieved leak rates of <5E-9 for a fiber coupled butterfly package. This offers the potential of reducing the length  of lifetime tests in certain applications.
Optocap’s expertise and capability in Encapsulation and Hermetic Sealing will reduce risk and reduce time to market as well as providing a cost-effective manufacturing option.

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