Wire Bonding Method Reducing Loop Height via Embedding
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Solution Overview
Problem
Current wire bonding methods struggle to form low loops with heights not exceeding two times the wire diameter while maintaining sufficient pull strength, as they require a wire turnover portion that increases thickness and makes it difficult to achieve the desired loop height.
Innovation Solution
A wire bonding method that involves forming a contact-bonded ball at the first bonding point and then pressing the side surface of the upper portion of the ball to create a protruded portion, followed by forming a wire drawing portion, allowing the wire to extend horizontally from the top of the contact-bonded ball, thereby reducing loop height and maintaining pull strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a wire turnover portion is formed to maintain pull strength, then the pull strength is sufficient, but the loop height increases and exceeds the desired limit
Solution Approach 1:
The invention transitions from a traditional wire turnover structure (requiring vertical height) to a wire embedding structure where the wire is drawn into the pad surface (utilizing horizontal/dimensional embedding). This dimensional change allows pull strength to be maintained through embedding depth rather than turnover height, thereby reducing loop height to within two times the wire diameter.
Solution Approach 2:
The wire is drawn into the pad surface before final bonding completion, creating a wire embedding portion that预先 establishes the pull strength mechanism. This preliminary embedding action eliminates the need for subsequent wire turnover operations, directly achieving both sufficient pull strength and reduced loop height.
2Length of moving object
If the loop height is reduced to not exceed two times the wire diameter, then the low profile is achieved, but the pull strength becomes insufficient
Solution Approach 1:
Instead of relying on vertical wire turnover for pull strength, the invention embeds the wire horizontally into the pad surface. The pull strength is derived from the embedding depth and lateral adhesion rather than vertical loop structure, enabling low loop height while maintaining sufficient pull strength.
Solution Approach 2:
The invention changes the critical parameter for pull strength from loop height to embedding depth. By controlling the wire drawing depth into the pad surface, sufficient pull strength is achieved without requiring increased loop height, thus satisfying the low profile requirement of not exceeding two times the wire diameter.
3Ease of manufacture
If conventional wire bonding methods are used, then the process is simple, but the loop height cannot be reduced below two times the wire diameter
Solution Approach 1:
The wire drawing operation is performed as a preliminary step before final bonding, creating the embedding portion that enables subsequent low-loop formation. This preliminary action integrates the loop height reduction into the bonding process itself, maintaining process simplicity while achieving the required loop height specification.
Data Source
AI summary
The invention provides a wire bonding method which enables formation of a low loop having a height not exceeding two times the wire diameter and secures sufficient pull strength of the wire even with the low loop shape. After having formed a contact-bonded ball at a first bonding point, a capillary moves upward and then toward a second bonding point to press a side surface of an upper portion of the contact-bonded ball, so that a protruded portion is formed on a top portion of the contact-bonded ball on the side of the second bonding point. After having formed the protruded portion of the contact-bonded ball, the capillary moves upward, and then downward while moving toward the second bonding point to press the protruded portion, so that a wire drawing portion for drawing the wire from the top portion of the contact-bonded ball horizontally is formed.