Aluminum wire with a diameter of 1.0mil is usually used in bonding. The selection of wire diameter depends on the bonding pad size. With Alpha IC, as the pad size is small, it is not recommended to use aluminum wire whose diameter exceeds 1.25mil.

In addition to wire diameter, aluminum wire has another important parameter called Tensile Strength (TS), which indicates the maximum tensile force that the wire can bear. This parameter can be found on the package of the wire. Bonding wires are divided into three types according to the TS value range. Wire with a TS value of 13 to 15 gram is called soft wire; wire with a TS value of 15 to 18 gram, normal wire, and wire whose TS value is 18 to 21 gram, hard wire.

A bonding wire with smaller TS can reduce the bonding power. So it is recommended to use bonding wires whose TS value is 13 to 15, or 15 to 18 (namely, the normal wire and the soft wire).

 

Generally, the diameter of the wedge hole is 2 times that of the wire. For instance, for 1.0mil wire, a 2020 wedge should be used. Here the first 20 means that diameter of the wedge hole is 2.0mil, and the second 20 means the length of the wedge soldering surface is 2.0mil. You can select the wedge according to your actual needs. The recommended wedges include 2015 and 2020 wedges. Note that with “Gaiser” wedges, there is a distinction between ELBR wedges and non-ELBR wedges. ELBR wedges have a smooth edge, which is good for wire feeding.

 

The bonding parameters of different bonders vary with one another. The common bonding procedure is as follows: First, set the bonding pressure. Then, adjust the power and time of the ultrasonic bonder according to the bonding shape. The ideal bonding shape width is 1.5 times of the bonding wire, while the bonding shape length is determined by the wedge. Finally, test the tensile strength of the bonding wire, which should be 3 to 5 grams.

The commonly used bonding parameters are as follows:

If problems like the IC is damaged or large current occur during bonding, this means you should increase pressure and reduce power for the bonder.