Ball Forming Device Current Control for Wire Bonding
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Solution Overview
Problem
Conventional wire-bonding apparatuses often produce deformed balls due to constant current supply, resulting in formations such as bubbles, shrinkage cavities, and eccentricity, especially when using wires made from certain materials.
Innovation Solution
A ball forming device that supplies a ball-forming current with a predetermined period including a first period of constant current and a second period featuring a triangle wave, which controls the current to stabilize the ball formation and reduce surface irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If constant current is supplied during ball formation, then the ball diameter can be controlled, but deformed balls with bubbles, shrinkage cavities, and eccentricity occur
Solution Approach 1:
The patent applies periodic action by dividing the ball formation process into multiple current supply periods with different current values. Instead of using constant current throughout, the method supplies current in periodic pulses where the current value changes between periods. This periodic current supply allows the molten metal to undergo repeated melting and solidification cycles, which eliminates deformation issues while maintaining diameter control.
Solution Approach 2:
The patent implements parameter changes by varying the current value between different supply periods. The current value is changed from a first value in the first period to a second value in the second period, and potentially to a third value in a third period. This dynamic parameter adjustment enables control over both ball diameter and internal structure quality, preventing defects like bubbles and shrinkage cavities.
2Device complexity
If constant current value is used for ball formation, then the process is simple, but surface irregularities and deformations occur
Solution Approach 1:
The patent uses periodic action to create multiple current supply periods with varying current values. This periodic variation in current causes repeated melting and solidification of the ball surface, which effectively flattens surface irregularities and eliminates deformations. The method maintains reasonable process complexity while dramatically improving surface quality.
3Productivity
If single-period current supply is used, then the formation process is fast, but ball deformation occurs
Solution Approach 1:
The patent divides the ball formation process into multiple current supply periods with different current values, creating a periodic action pattern. This multi-period approach allows the ball to undergo repeated melting and solidification cycles, which eliminates deformation issues. While the process takes longer than single-period methods, it achieves both acceptable formation speed and high shape accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the stable formation of balls with a predetermined diameter, suppressing deformation issues like bubbles, shrinkage cavities, and eccentricity by repeatedly melting and solidifying the ball surface with the triangle wave current, ensuring consistent ball shape and size.
Implementation Method 1
discharge is produced between an electrode and a tip of a wire inserted through a bonding tool (e.g., capillary) to form a ball at the tip of the wire
Implementation Method 2
producing discharge between an electrode and the tip of the wire
Implementation Method 3
melting (fusion) and solidification are repeatedly performed over a surface of the ball formed during the first period
Implementation Method 4
melting (fusion) and solidification are repeatedly performed over a surface of the ball
Implementation Method 5
surface tension is produced for a plurality of times. Therefore, it is possible to flatten irregularity and deformation of the surface
Data Source
AI summary
A ball forming device 50 for forming a ball 43 at a tip of a wire 42 by producing discharge between a torch electrode 48 and the tip of the wire 42, the device includes: a current supply unit 54 configured to supply a ball-forming current between the torch electrode 48 and the tip of the wire 42; and a current control unit 57 configured to control the current supply unit 54, so that a signal of the ball-forming current for a predetermined period includes a first period in which the signal takes a predetermined current value and a second period including a triangle wave. With this, it is possible to provide a ball forming device, a wire-bonding apparatus, and a ball formation method that are capable of suppressing formation of deformed balls.