Circuit Board Surface Plating for Wire Bonding and Solder Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for manufacturing circuit boards face challenges in achieving high reliability, particularly during temperature cycling, due to inadequate soldering performance on the lower surface of the lead frame, which can lead to reduced reliability in semiconductor assembly processes, especially for applications requiring high reliability like automotive products.
Innovation Solution
A method involving the preparation of a substrate with electrical conductivity, forming pillars on one surface, applying insulating material, and using different metal layers on opposite surfaces through plating processes, where the upper surface is plated with silver or silver alloys and the lower surface is plated with materials like nickel or gold alloys to enhance copper wire bonding and soldering performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lower surface of the lead frame is not plated with metal material, then copper wire bonding performance on the upper surface is maintained, but soldering performance on the lower surface is insufficient and reliability is reduced during temperature cycling
Solution Approach 1:
The patent applies different metal plating materials to different surfaces of the lead frame: silver plating on the upper surface for optimal copper wire bonding, and nickel or gold alloy plating on the lower surface for optimal soldering performance. This local differentiation allows each surface to have the specific properties needed for its function, resolving the contradiction between wire bonding performance and soldering performance.
2Ease of manufacture
If the lower surface of the lead frame is plated with metal material to improve soldering performance, then soldering performance is improved, but copper wire bonding performance between semiconductor chip and bonding area is reduced
Solution Approach 1:
The patent selectively plates only specific areas of the lead frame with different materials: the bonding area on the upper surface is plated with silver for optimal wire bonding, while the lower surface is plated with nickel or gold alloy for soldering. By controlling the location and material type of plating, the patent ensures that wire bonding performance is not compromised while achieving good soldering performance.
3Ease of manufacture
If an additional plating process is performed on the lower surface to improve soldering performance, then soldering performance is improved, but intermetallic compound characteristics are not good and reliability is still reduced
Solution Approach 1:
The patent changes the material parameter of the plating layer on the lower surface from conventional materials to specifically nickel or gold alloy materials. This material parameter change results in superior intermetallic compound characteristics and reliability during temperature cycling, while also providing adequate soldering performance. The patent identifies specific material compositions that simultaneously satisfy both soldering performance and reliability requirements.
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 improves both copper wire bonding and soldering performance, enhancing the reliability of the circuit board during temperature cycling and semiconductor assembly, without the need for additional plating processes, thus addressing the limitations of existing methods.
Implementation Method 1
forming a first metal layer on the first surface of the substrate, and forming a second metal layer on the second surface of the substrate
Data Source
AI summary
A method of manufacturing a circuit board includes preparing a substrate having electrical conductivity, removing a portion of a first surface of the substrate to form a plurality of pillars on the first surface of the substrate, locating an insulating material on the first surface of the substrate to cover a space between the plurality of pillars of the substrate, forming a pattern on a second surface, which is opposite to the first surface of the substrate, by removing a portion of the second surface of the substrate, forming a first metal layer on the first surface of the substrate, and forming a second metal layer on the second surface of the substrate.