Wire type and size
Careful evaluation of wire type and size is necessary to ensure proper wire bonding to the PCB. The type of wire includes the type of material to be used and its corresponding purity and alloy composition. Improper selection of wire type and size may lead to reliability failures. For devices with fine spacing, smaller wire sizes are required and they are more sensitive to swinging or short circuiting with adjacent wires.
Capillary type
The capillary used plays a crucial role in the performance of PCB wire bonding process. Some characteristics of capillaries, such as chamfer diameter and face angle, determine the formation of balls and wedges during wire bonding. Incorrect capillary geometry can lead to serious problems such as bonding smearing, excessive bonding, and weld or pin breakage.
clean surface
The surface of the wire to be soldered must be clean and free of contaminants, otherwise it may interfere with the bonding between the wire and the solder pad. Sometimes plasma cleaning is used to clean and pre treat the contact area, thereby achieving effective wire bonding. Contaminated PCB wire bonding areas may result in lower wire tension and bonding shear force test results. For copper wire bonding, it is important to use synthetic gas or nitrogen to avoid oxidation.
Wire bonding machine parameters
It is necessary to optimize the main PCB wire bonding parameters (such as wire bonding force, power, and time) to achieve high-quality wire bonding surfaces. Excessive power or force can cause wire bonding pads to "sink" or even crack, while a lack of the same parameters can result in non stick and low tensile test results. We are conducting design experiments and parameter screening to understand the acceptable ranges of force, power, and time.
