Wire Bond Stiffening via Selective Non-Conductive Coating
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Solution Overview
Problem
The challenge in reducing material costs for integrated circuit production without compromising performance, particularly in high-density wire bond designs, is the risk of wire shorts due to reduced wire lengths and encapsulation-induced wire movement.
Innovation Solution
A method involving the selective application of a non-conductive material, such as epoxy, to specific regions of high-density wire bonds to prevent shorting, where the material is applied in multiple segments and cured to form beads that stabilize the wires during encapsulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If wire bond length is reduced to lower material cost, then material cost decreases, but wire-to-wire gap decreases leading to wire shorts
Solution Approach 1:
The patent applies non-conductive material selectively to specific regions where wire bonds are in close proximity or cross over each other, rather than coating all wire bonds uniformly. This localized application prevents wire shorts in critical areas while minimizing material usage and cost.
Solution Approach 2:
The non-conductive material acts as an intermediary substance between adjacent wire bonds, preventing direct contact and electrical shorting. This mediator allows the wire bonds to be placed closer together without compromising reliability.
2Ease of manufacture
If conventional encapsulation is used to protect the circuit, then encapsulation is applied, but wire sweep or movement occurs leading to wire shorts
Solution Approach 1:
The non-conductive material is applied to the wire bonds before the encapsulation process. This preliminary coating prevents wire sweep during molding by providing friction and mechanical support, ensuring wires remain in their intended positions throughout the encapsulation process.
Solution Approach 2:
The non-conductive material serves as a protective cushion between the wire bonds and the encapsulation material, preventing direct contact that could cause wire movement or shorting during the encapsulation process.
3Reliability
If non-conductive material is applied to all wire bonds, then wire short prevention is improved, but material usage and process complexity increase
Solution Approach 1:
The patent implements selective coating of wire bonds based on their spatial relationships, coating only those wires that are in close proximity or cross over each other. This approach maintains wire short prevention where needed while simplifying the overall process by avoiding unnecessary coating of all wires.
Solution Approach 2:
Instead of coating all wire bonds, the patent applies non-conductive material only to the extent necessary - specifically to wires in high-risk areas for shorting. This partial action achieves the required reliability without the complexity of a complete coating process.
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 significantly reduces wire sweep and electrical shorts, improving yield and maintaining minimal wire-to-wire gaps, resulting in a 16% to 169% increase in wire gap and a 44% reduction in wire sweep defects.
Implementation Method 1
curing the non-conductive material by heating the non-conductive material
Data Source
AI summary
A method of assembling an integrated circuit package is disclosed. The method comprises placing a die on a substrate of the integrated circuit package; coupling a plurality of wire bonds from a plurality of bond pads on the die to corresponding bond pads on the substrate; applying a non-conductive material to the plurality of wire bonds; and encapsulating the die and the plurality of wire bonds. An integrated circuit package is also disclosed.