PCB Pad Insulating Walls for High-Density Die Bonding
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Solution Overview
Problem
The miniaturization and high performance of semiconductors have led to increased precision requirements for solder resist openings and solder bumps, making it difficult to prevent bridge shorts during die bonding.
Innovation Solution
A printed circuit board design where the side surfaces of pads for mounting dies are covered by insulating walls, reducing the risk of bridge shorts and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the distance between connection terminals is decreased to achieve high-density mounting, then mounting density is improved, but the risk of bridge shorts increases
Solution Approach 1:
An insulating wall is introduced as an intermediary structure between adjacent pads. This insulating wall extends from the insulating layer to cover the side surfaces of the pads, physically separating adjacent connection terminals and preventing solder bridges while allowing high-density mounting to proceed
Solution Approach 2:
The insulation structure transitions from a two-dimensional planar solder resist pattern to a three-dimensional vertical insulating wall that covers the side surfaces of pads. This dimensional change allows insulation to occur in the vertical dimension rather than relying solely on horizontal spacing, enabling closer terminal spacing without increasing bridge short risk
2Manufacturing precision
If the precision of solder resist openings is increased to accommodate miniaturization, then mounting precision is improved, but manufacturing difficulty increases
Solution Approach 1:
The insulation function is moved from the horizontal plane (solder resist openings) to the vertical dimension (insulating walls covering side surfaces). This reduces the critical precision requirements for planar features while maintaining effective isolation, as the insulating walls can be formed with less stringent dimensional tolerances
Solution Approach 2:
Instead of requiring high precision across the entire solder resist opening pattern, the insulating walls provide localized insulation precisely where needed at the pad side surfaces. This allows other areas to have more relaxed manufacturing tolerances, reducing overall manufacturing difficulty
3Adaptability or versatility
If the size of solder bumps is reduced to match miniaturized dies, then mounting compatibility is improved, but the difficulty of forming solder bumps increases
Solution Approach 1:
The insulating wall acts as a mediator that stabilizes the interface between the reduced-size solder bumps and the pad. By covering the side surfaces, it provides mechanical support and defines the bonding interface, making it easier to form and control small solder bumps while maintaining reliable connections
Data Source
AI summary
A printed circuit board includes: an insulating layer; a plurality of pads disposed on the insulating layer; and a plurality of insulating walls disposed on the insulating layer, and at least partially covering side surfaces of the plurality of pads, respectively, while being free from surfaces of the plurality of pads, respectively. The plurality of insulating walls are disposed to be spaced apart from each other on the insulating layer.