Reverse Ball Bonding for Semiconductor Chip Layout Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor memory card manufacturing, existing wire bonding methods face challenges such as limited flexibility in chip layout, increased mounting area requirements, and reduced packaging density due to issues with wire contact and deformation during resin molding, especially when dealing with thin chips and small electrode pads.
Innovation Solution
The implementation of a wire bonding method that uses reverse bonding with ball bonding, allowing connections in two directions on small pads without requiring rectangular pads, and optimizing wire routing to reduce wire length and improve packaging density by using marks for precise wire placement and connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If forward bonding or reverse bonding is used to connect semiconductor chips to substrate electrodes, then electrical connection is achieved, but wire contact and deformation occur during resin molding when chips are thin and electrode area is small
Solution Approach 1:
The patent applies reverse bonding (bonding from substrate to chip) instead of forward bonding (bonding from chip to substrate). This inversion of the bonding direction allows the wire to be pulled taut during the process, preventing wire loop formation and subsequent contact/deformation during resin molding, while maintaining reliable electrical connection
2Area of stationary object
If wire bonding is performed on small electrode pads, then connection is achieved, but flexibility in chip layout is limited and mounting area increases
Solution Approach 1:
By using reverse bonding where the bonding tool approaches from the substrate side rather than the chip side, the method enables wire routing that is less constrained by chip position, thereby increasing layout flexibility without requiring larger mounting areas
3Reliability
If conventional wire bonding methods are used, then electrical connection is established, but packaging density is reduced due to wire deformation and contact issues
Solution Approach 1:
The reverse bonding approach eliminates wire loop formation by pulling the wire taut during bonding from the substrate side, preventing wire deformation during resin molding. This results in more compact packaging with improved density while maintaining reliable electrical connections
Solution Approach 2:
The wire is tensioned and positioned correctly during the reverse bonding process itself, performing the wire straightening action preliminarily before resin molding occurs, thereby preventing subsequent deformation and contact issues
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 enhances the degree of freedom in chip and terminal layout, reduces the cost of chip lamination, and improves packaging density by allowing flexible wire routing without wire contact issues, effectively addressing the limitations of traditional methods.
Implementation Method 1
The point of ball state of the first wire is connected to the first electrode, a part of the first wire is connected to the second electrode
Data Source
AI summary
The degree of freedom of the chip layout in a semiconductor device is improved, and improvement in packaging density is aimed at.Since it becomes possible to form the wire of two directions on the pad of a memory chip by performing the over-bonding of reverse bonding by ball bonding, an effect equivalent to continuation stitch bonding of wedge bonding can be produced by ball bonding. Hereby, the degree of freedom of a chip layout and the degree of freedom of the lead layout of substrate 3 can be improved, and the packaging density on a substrate in a chip lamination type semiconductor device (memory card) can be improved.