User:Spheroidite/Wedge bonding

Wedge bonding, a type of wire bonding, is the process of welding wires or ribbons to substrates of various materials to form electronic interconnections through the application of ultrasonic energy and force over time. Wedge bonding is categorized either fine or heavy wire bonding based on the wire size or as ribbon bonding. Wedge bonding is suited for different applications and requires different manufacturing equipment and approaches.

Bond characteristics
Fine (thin) wire bonding uses wire diameters 12.5 to 75 μm, whereas heavy (thick) wire refers to wire sizes 75 to 600 μm.

The wire bonded joint is made up of the wedge, the deformed wire contact attached to the substrate, the heel (also known as neck), the junction between the wedge and the loop, the loop, the length of wire bridging between the bond contacts, and the tail, the extra length of wire sticking off the end of the first (source) bond.

Dimensional acceptability
Acceptability of bonds is defined by industry, military, or internal company standards.

Loops must have a separation clearance of at least 2 times the wire diameter.

Visual acceptability
Heel notches, wire fragments, residue or scratches under the bond, and tool marks are not allowed. Bonds may not be double-bonded.

Pull test acceptability
The pull test limits depend on the type and material properties of the wire. For fine wire, pull force must be greater than 0.3 times the breaking load for destructive testing, and greater than 0.2 times the breaking load for non-destructive testing, whereas for heavy wire the pull force must be greater than 0.75 times the breaking load for destructive testing, and greater than 0.5 times the breaking load for non-destructive testing. The minimum pull test limits for non-destructive and destructive.

Shear test acceptability

 * Minimum shear force = 2*BL
 * Minimum bond coverage >50%

Quality requirements
Typical requirements in terms of process capability are e.g. automotive long-term load (1.33), automotive short-term load (1.67), consumer (1.33) and industrial (1.33).

$$C_{pk}=\frac{min(\mu-LSL;USL-\mu)}{3\sigma}$$

Bonding parameters are developed using the design of experiments method evaluating the visual, dimensional, and test results.

Wire bond equipment
Leading manufacturers of wire bonders are Hesse Mechatronics, F&K Delvotec, and Kulicke & Soffa.

Bond wire
Major suppliers of bond wire are Heraeus and Tanaka.

Wedge tools
Major suppliers of wedge tools are Small Precision Tools (SPT), Micro Point Pro (MPP), and Deweyl.

Standards


Category:Semiconductor device fabrication Category:Packaging (microfabrication) Category:Welding Category:Electronics manufacturing