Selective Bond Wire Coating for Molding-Induced Short Prevention
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Solution Overview
Problem
In multi-die IC packages, long wires connecting stacked dies to a substrate are prone to deformation during the molding process, leading to electrical shorts due to wire sweeps by the molding compound.
Innovation Solution
Selectively coating bond wires with an electrically insulating polymer based on specific criteria, such as length, diameter, orientation, and deformation tendency, to prevent short circuits, and using a specialized wire-bonding tool for polymer coating and bare wire production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long wires are used to connect stacked dies to substrate, then electrical connections can be established for multi-die packages, but wire deformation and short circuits occur during molding
Solution Approach 1:
The patent applies selective polymer coating to specific segments of bond wires based on their susceptibility to deformation. Rather than coating all wires uniformly, the system identifies high-risk wire segments (those with greater length, specific orientations, or positioned in high-stress areas) and applies insulating polymer coating only to those segments, providing localized protection against short circuits while maintaining overall system reliability
Solution Approach 2:
The patent performs wire coating with insulating polymer before the molding process. By pre-coating the identified high-risk wire segments with electrically insulating material, the system prepares protective measures in advance that prevent short circuits from occurring during the subsequent molding operation, rather than attempting to fix problems after they arise
2Reliability
If selective polymer coating is applied to bond wires, then short circuits are prevented, but device complexity and manufacturing process complexity increase
Solution Approach 1:
The patent uses a wire-bonding tool with modified capillary structure that can deliver both bond wire and fluid polymer through integrated channels. By changing the physical parameters of the bonding tool (adding circumferential channels for polymer delivery) and controlling polymer dispensing parameters (volume, timing, location), the system achieves selective coating without requiring entirely separate coating equipment, thus managing complexity
Solution Approach 2:
The patent introduces a fluid polymer as an intermediary substance that provides electrical insulation between bond wires. This intermediary material acts as a mediator that prevents direct contact between wires during molding, solving the short circuit problem while allowing the existing wire bonding and molding processes to continue with minimal modification
3Reliability
If polymer coating is applied to bond wires, then manufacturing defects are reduced, but manufacturing time and process steps increase
Solution Approach 1:
The patent combines the wire bonding operation with the polymer coating operation into a single integrated process step. The modified wire-bonding tool delivers both the bond wire through a central channel and fluid polymer through circumferential channels, allowing coating to occur during or immediately after wire placement without requiring a separate coating process step, thus minimizing additional manufacturing time
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
The polymer coating effectively prevents unwanted short circuits by insulating wire contacts, ensuring reliable electrical connections and reducing manufacturing defects in semiconductor devices.
Implementation Method 1
a circumferential channel configured to deliver a fluid polymer from an inlet port to a first end of the approximately cylindrical body... and further having a cylindrical-sheet channel configured to coat a segment of the bond wire exiting the first end of the approximately cylindrical body with a layer of the fluid polymer
Data Source
AI summary
A semiconductor device wherein a selected subset of bond wires is coated with an electrically insulating polymer to reduce occurrences of electrical shorts caused by wire sweep in the flow of a molding compound during an encapsulation stage of the manufacturing process. In some examples, the bond wires to be coated are selected based on a set of criteria that flag the bond wires exhibiting a relatively high tendency towards forming such electrical shorts. A specialized wire-bonding tool that can be operated to produce both polymer-coated bond wires and bare bond wires is also provided.