Wire Bonder Lead Frame Vibration Control
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Solution Overview
Problem
The vibration of a lead frame during the wire bonding process in semiconductor manufacturing, caused by thermal shrinkage and uneven stress distribution due to abrupt cooling, leads to deformation and short-circuits, particularly when using gold wires with diameters less than 20 μm.
Innovation Solution
A method and apparatus for wire bonding that includes a heat block, a frame holding member, and a slow cooling mechanism to gradually decrease the temperature of the lead frame after wire bonding, along with guides or rollers to press and stabilize the lead frame, reducing vibration and stress-induced deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the lead frame is abruptly cooled after wire bonding, then the cooling time is reduced and productivity is improved, but the lead frame vibrates due to thermal shrinkage causing wire deformation and short-circuits
Solution Approach 1:
The patent applies preliminary action by pressing the lead frame with a pressing member before and during the cooling process. This pre-positioning constraint prevents the lead frame from vibrating due to thermal shrinkage when cooled, thereby avoiding wire deformation and short-circuits while maintaining efficient cooling timing
Solution Approach 2:
The pressing member provides preliminary anti-action by counteracting the thermal shrinkage force before it can cause vibration. By applying compressive force in advance during the cooling process, the system prevents the harmful vibration effect that would otherwise occur during abrupt cooling
2Loss of substance
If the wire diameter is reduced to less than 20 μm to reduce cost, then material cost is reduced, but the wire becomes more susceptible to deformation and short-circuits due to lead frame vibration
Solution Approach 1:
The pressing member provides beforehand cushioning by maintaining continuous contact with the lead frame during cooling. This cushioning effect absorbs and dampens the vibrations caused by thermal shrinkage, protecting the thin wire (≤20 μm) from deformation and short-circuits while allowing the use of cost-reduced thinner wire
3Manufacturing precision
If the lead frame is pressed by the frame holding member during wire bonding, then wire bonding quality is improved, but the lead frame cannot be released and fed to the rear stage
Solution Approach 1:
The pressing member is designed with dynamic characteristics, being movable in the vertical direction to press the lead frame during wire bonding and cooling, then movable in the horizontal direction to release and feed the lead frame to the rear stage. This dynamic capability allows the system to switch between the pressing function for precision and the feeding function for operational ease
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 improves the quality and reliability of wire bonding by minimizing lead frame vibration, reducing the occurrence of short-circuits, and maintaining the integrity of thin gold wires during the bonding process.
Implementation Method 1
wire bonding is performed over the heat block with the lead frame heated to approximately 230 to 240° C.
Implementation Method 2
the strip-like lead frame will bend (deform) so as to project upward with respect to the width direction due to thermal shrinkage
Implementation Method 3
cooling the lead frame so that the temperature thereof may decrease stepwise
Data Source
AI summary
An improvement in the quality of wire bonding is achieved by reducing the vibration of a lead frame or a wiring substrate after wire bonding. Over a heat block in a wire bond portion of a wire bonder, there is provided a cooling blower for cooling a wire-bonded matrix frame so that the temperature thereof may decrease stepwise. After wire bonding, cold air is blown from the cooling blower to the matrix frame, and temperature control of the matrix frame is performed so that the temperature of the matrix frame after wire bonding may decrease stepwise. Or, the wire-bonded matrix frame is fixed with a holding tool such as a frame holding member, a guide member, a roller means, or an elastic means until cooling is completed.