Bond Wire Separation via Non-Conductive Die Attach
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Solution Overview
Problem
Conventional chip packages are prone to electrical shorts due to the close proximity of bond wires, which increases the likelihood of wire-to-wire and wire-to-die shorting, especially as device and chip package sizes decrease, leading to interference, data errors, and chip damage.
Innovation Solution
The implementation of non-conductive die attaches made of materials that can be molded and cured to specific forms, positioned between bond wires and substrate fingers, to provide vertical pressure and friction, preventing sagging and shifting of bond wires, thereby reducing the risk of electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bond wires are manufactured to be extremely close to one another to reduce device size, then device density and integration are improved, but the likelihood of electrical shorting between bond wires increases
Solution Approach 1:
A non-conductive die attach material is introduced as an intermediary substance between the bond wires and the substrate. This material provides physical support and separation to the bond wires, preventing them from making contact with each other or the substrate, thereby eliminating the electrical shorting risk while allowing the wires to be positioned extremely close together for high device density
Solution Approach 2:
The die attach material is applied in advance to the substrate at the bond wire locations before the bond wires are attached. This creates a pre-positioned protective barrier that cushions and supports the bond wires, preventing future sagging, shifting, or contact with adjacent wires, thus preventing electrical shorts before they can occur
2Ease of manufacture
If bond wires are allowed to sag due to their own weight, then manufacturing process is simpler, but electrical shorts between wires or to the die occur
Solution Approach 1:
The non-conductive die attach material serves as an intermediary support structure between the bond wires and the substrate. It provides continuous physical support along the wire path, counteracting the wire's own weight and preventing sagging, while maintaining electrical isolation and preventing shorts to the die or adjacent wires
Solution Approach 2:
The die attach material changes the mechanical parameters of the bond wire system by providing continuous support that eliminates wire sagging. This transforms the wire from a freely hanging conductor subject to gravitational force into a supported conductor with maintained spatial separation, preventing electrical shorts while keeping the manufacturing process simple
3Reliability
If reverse-loop configuration is used to increase clearance between wires, then wire separation is improved, but the wire remains prone to sagging due to long flat wire portions
Solution Approach 1:
The die attach material is positioned at critical locations along the bond wire path, including under the reverse-loop configuration. It provides localized support that maintains the increased clearance between wires while preventing the long flat wire portions from sagging, combining the benefits of both configurations
Solution Approach 2:
Rather than requiring the entire wire to be in a rigid configuration, the die attach material provides localized support at specific points along the wire path. This allows the wire to maintain reverse-loop clearance in critical areas while being supported against sagging at other locations, optimizing both clearance and stability
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 solution significantly reduces the chances of electrical shorts, enhances the reliability and lifespan of multi-chip packages, allows for closer manufacturing of bond wires and lead fingers, increases data throughput, and improves product density while reducing manufacturing costs.
Implementation Method 1
The non-conductive die attach (290) may be made of any non-conductive material known to those of skill in the art, and may be formed to provide friction between the bond wire (220, 260) and the substrate (250), thereby preventing sagging and/or shifting of the bond wire (220, 260).
Data Source
AI summary
A multi-chip package is disclosed that has a construction capable of preventing and/or reducing electrical shorts caused by shifts in bond wires. The multi-chip package includes a die attach formed between connection points of a bond wire. The die attach is made of a non-conductive material and can be constructed so as to support or encompass a portion of the bond wire. By contacting the bond wire, the die attach restricts the motion of the bond wire by acting as a physical barrier to the bond wire's movement and/or as a source of friction. In this manner, undesired position shifts of the bond wires can be prevented, reducing device failures and allowing for improved manufacturing allowances.