Wire Bonding Pad Coating for Stable Chip Package Welding
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Solution Overview
Problem
Existing chip packaging technologies face issues with unreliable and unstable wire bonding due to surface conditions, oxidation, dirt, and metal thickness of bonding pads, leading to anomalies like false welding and weak connections.
Innovation Solution
A chip packaging structure featuring a substrate with a metal bonding pad coated with a ring-shaped solder layer, where the metal wire's tail end is welded into the coating layer, ensuring stable connection between the wire and pad, and a method involving electroplating and reflow soldering to enhance bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional wire bonding is used without additional protective layers, then the manufacturing process is simple, but the welding reliability is poor due to surface conditions, oxidation, and process parameter variations
Solution Approach 1:
The patent applies composite materials by creating a multi-layer structure consisting of the metal bonding pad, coating layer, and passivation layer. The coating layer (e.g., tin) is formed over the bonding pad surface, and the passivation layer provides additional protection. This composite structure improves welding reliability by protecting the bonding pad from oxidation and surface defects while maintaining electrical and mechanical performance.
Solution Approach 2:
The patent applies preliminary action by forming the coating layer and passivation layer on the bonding pad before the wire bonding process. The coating layer is deposited and patterned in advance to create a protected bonding surface, and the passivation layer is formed subsequently to seal and protect the entire structure. These preliminary protective measures ensure reliable welding by preventing surface degradation before the bonding operation occurs.
2Reliability
If the bonding pad surface is left exposed, then the manufacturing process is straightforward, but false welding and weak welding occur due to oxidation and surface roughness
Solution Approach 1:
The patent uses composite materials by depositing a coating layer (such as tin) over the metal bonding pad and subsequently forming a passivation layer. This multi-layer composite structure protects the bonding pad surface from oxidation and reduces surface roughness, thereby improving welding stability and reducing false welding defects while maintaining manufacturability through standard semiconductor fabrication processes.
Solution Approach 2:
The passivation layer acts as an inert barrier that protects the bonding pad and coating layer from environmental oxidation and contamination. By providing this protective environment, the patent ensures stable welding performance and reduces defects caused by surface oxidation without significantly complicating the manufacturing process.
3Manufacturing precision
If no coating layer is applied on the bonding pad, then the structure is simple, but the welding quality is affected by surface conditions and oxidation
Solution Approach 1:
The patent applies composite materials by forming a coating layer (e.g., tin) on the metal bonding pad and subsequently depositing a passivation layer. This composite structure improves welding quality by providing a controlled, oxidation-free surface with consistent electrical and mechanical properties, while the layered structure is integrated into the existing semiconductor fabrication process flow.
Solution Approach 2:
The patent applies local quality by selectively forming the coating layer and passivation layer only in the wire bonding area of the bonding pad, while leaving other areas (such as the solder area) exposed or differently treated. This localized approach improves welding quality where needed without unnecessarily complicating the overall structure or affecting other functional areas.
4Reliability
If the metal wire is welded directly to the bonding pad surface, then the process is simple, but false welding and weak welding occur due to surface oxidation and roughness
Solution Approach 1:
The patent applies preliminary action by forming the coating layer and passivation layer on the bonding pad before performing the wire bonding process. The coating layer is deposited and patterned in advance to create a protected bonding surface, and the passivation layer is formed subsequently to seal and protect the entire structure. These preliminary protective measures ensure reliable welding by preventing surface degradation before the bonding operation occurs.
Solution Approach 2:
The patent uses composite materials by creating a multi-layer structure consisting of the metal bonding pad, coating layer, and passivation layer. The coating layer (e.g., tin) is formed over the bonding pad surface, and the passivation layer provides additional protection. This composite structure improves welding reliability by protecting the bonding pad from oxidation and surface defects while maintaining electrical and mechanical performance.
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 solution significantly improves the welding reliability and stability between the metal wire and bonding pad, reducing anomalies and enhancing product quality by forming a robust solder joint that avoids false and weak welds.
Implementation Method 1
preparing a metal bonding pad in the metal bonding pad forming area by an electroplating method
Implementation Method 2
melting the solder by heating and enabling the solder to enter the wire bonding area, so as to form a coating layer wrapping the welding part
Data Source
AI summary
The present invention provides a chip packaging structure and a chip packaging method. The chip packaging structure includes a substrate, a metal bonding pad disposed on the substrate and a metal wire, wherein the tail end of the metal wire is provided with a welding part, the welding part is welded to the metal bonding pad, the metal bonding pad is provided with a coating layer, and at least part of the welding part is located between the coating layer and the metal bonding pad. The present invention greatly improves a welding effect of the metal wire and the metal bonding pad, so that the welding of the metal wire and the metal bonding pad is more reliable and stable.