Roughened Copper Lead Surfaces for Plating-Free Wire Bonding
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Solution Overview
Problem
Semiconductor packages face issues with weak connections between bond wires and leads due to oxidation of copper leads, leading to detachment and delamination, and the use of precious metal plating to prevent oxidation increases costs without post-manufacture benefits.
Innovation Solution
The semiconductor package features a conductive component with a roughened surface, eliminating the need for precious metal plating by directly coupling bond wires to the roughened surface, which is treated with an anti-tarnish chemical coat that decomposes during the thermosonic bonding process, enhancing mechanical connections without increasing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If precious metal plating is applied to copper leads to prevent oxidation, then reliability of connection is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the precious metal plating layer from the conventional structure, exposing the roughened copper surface directly. This extraction eliminates the need for expensive plating materials while maintaining connection reliability through the roughened surface morphology that enhances mechanical interlocking and electrical contact.
Solution Approach 2:
The patent applies a roughened surface treatment specifically to the bond wire attachment area of the copper lead, creating localized surface irregularities that enhance mechanical interlocking. This local modification provides oxidation resistance and bonding strength at the critical interface without requiring expensive precious metal plating over the entire surface.
2Ease of manufacture
If copper leads are used to reduce cost, then manufacturing cost decreases, but oxidation occurs leading to weak connections
Solution Approach 1:
The patent applies a roughening treatment to the copper lead surface before the bonding process. This preliminary surface modification creates a morphology that enhances mechanical interlocking and provides oxidation resistance, ensuring reliable bonding occurs before oxidation can degrade the connection. The roughened surface is prepared in advance to receive the bond wire attachment.
Solution Approach 2:
The patent modifies the surface morphology parameter of the copper lead by creating a roughened surface with specific topography. This parameter change increases surface area, enhances mechanical interlocking capability, and provides oxidation resistance, allowing copper to maintain reliability without precious metal plating.
3Ease of manufacture
If smooth surface is used on conductive components, then ease of manufacturing is improved, but mechanical connection strength decreases
Solution Approach 1:
The roughening treatment is applied as a preliminary step before bonding, creating the desired surface morphology in advance. This allows the subsequent bonding process to take advantage of the enhanced surface topology for mechanical interlocking without adding complexity to the bonding operation itself.
Solution Approach 2:
The patent changes the surface morphology parameter from smooth to roughened, creating topographic features that enhance mechanical interlocking. This parameter modification increases the effective bonding area and provides anchor points for the bond wire, significantly improving mechanical connection strength.
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 strengthens mechanical connections between bond wires and conductive components, reduces the risk of delamination, and lowers production costs by eliminating the need for precious metal plating while maintaining structural and functional integrity.
Implementation Method 1
applying heat to the roughened surface to cause an anti-tarnish chemical coat abutting the roughened surface to decompose
Implementation Method 2
causing the decomposed anti-tarnish chemical coat to slough off of the roughened surface using at least one of mechanical and ultrasonic energy
Implementation Method 3
causing the bond wire to adhere directly to the roughened surface without a precious metal positioned therebetween
Data Source
AI summary
In some examples, a semiconductor package comprises a die pad, a semiconductor die on the die pad, and a mold compound covering the die pad and the semiconductor die. The semiconductor package includes a conductive component including a roughened surface, the roughened surface having a roughness ranging from an arithmetic mean surface height (SA) of 1.4 to 3.2. The mold compound is coupled to the roughened surface. The semiconductor package includes a bond wire coupling the semiconductor die to the roughened surface. The bond wire is directly coupled to the roughened surface without a precious metal positioned therebetween.