Wire Bonding Method for Low-Profile Looping
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Solution Overview
Problem
Existing wire bonding techniques, such as forward and reverse bonding, face challenges in meeting low-profile looping requirements while maintaining manufacturing efficiency, with forward bonding prone to neck cracks and reverse bonding being discontinuous and slower.
Innovation Solution
A wire bonding method involving the formation of a metal ball bump on a substrate's finger, followed by a wire formed from the bump to a pad, with a free air ball created by electronic flame-off and pressed onto the pad, positioning the wire between the ball and pad to reduce loop height and enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If forward bonding is used, then bonding speed and fine pitch capability are improved, but loop height increases causing neck cracks and reliability problems
Solution Approach 1:
The patent inverts the conventional forward bonding sequence by first forming a ball bond on the substrate, then forming a capillary that creates a stitch bond back to the chip pad. This reverse sequence allows the wire to be supported by the initial ball bond, eliminating the neck area vulnerability while maintaining bonding efficiency and enabling low-profile looping.
2Shape
If reverse bonding is used, then low-profile looping is achieved, but the process becomes discontinuous and much slower
Solution Approach 1:
The patent achieves continuous bonding by forming the ball bond and subsequent capillary/stitch bond in an uninterrupted sequence without removing the chip or repositioning components. This continuous process eliminates the discontinuities inherent in traditional reverse bonding, maintaining high productivity while achieving low-profile looping through the inverted bonding sequence.
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 method simplifies the manufacturing process, reduces wire loop height, and improves efficiency by allowing continuous bonding without initial bump placement, meeting low-profile requirements while speeding up the wire bonding process.
Implementation Method 1
a first free air ball is formed on the first wire by electronic flame-off process
Implementation Method 2
a first wire is formed from the metal ball bump toward the corresponding first boding pad
Data Source
AI summary
A wire bonding method includes the following steps. First, a substrate including at least one metal finger is provided. Next, a first chip including at least one first boding pad is disposed on the substrate. Next, a metal ball bump is formed on the corresponding metal finger. Next, a first wire is formed from the metal ball bump toward the corresponding first boding pad. Next, a first free air ball is formed on the first wire by electronic flame-off process. Then, the first free air ball connected to the first wire is pressed on the corresponding first boding pad, such that the first wire is located between the first free air ball and the corresponding first boding pad.