PCB Resist Protrusion for Bump Bonding Short-Circuit Prevention
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Solution Overview
Problem
In bump bonding structures, defects such as short-circuiting can occur due to volume control issues with solder balls, abnormal shapes, or misalignment of dies and substrates.
Innovation Solution
A printed circuit board design that includes a protrusion acting as a dam around the opening exposing a pad, formed by a post around the outermost pad of the substrate covered with a resist layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bump bonding structure is used to connect die and substrate, then electrical connection is achieved, but short-circuit defects occur due to solder ball volume control issues, abnormal shapes, or misalignment
Solution Approach 1:
The patent introduces a resist layer as an intermediary substance between the solder balls and the substrate surface. This resist layer forms protrusions that act as physical barriers and dams, preventing solder balls from moving or deforming in ways that would cause short-circuits. The intermediary layer absorbs and compensates for alignment errors and volume variations without allowing harmful contact between adjacent solder balls.
Solution Approach 2:
The resist layer is applied to the substrate surface before the bump bonding process. This preliminary action creates pre-formed protrusions and dams that define the acceptable range of solder ball placement. By establishing these protective structures in advance, the system prevents short-circuit defects before they can occur during or after the bonding process, rather than attempting to correct issues after they arise.
2Object-affected harmful factors
If solder ball volume is controlled tightly to prevent short-circuits, then short-circuit defects are reduced, but manufacturing complexity increases due to precise volume and shape control requirements
Solution Approach 1:
The resist layer serves as a mediator that decouples the relationship between solder ball dimensions and short-circuit prevention. Instead of requiring extremely precise control of solder ball volume and shape, the resist layer's protrusions provide a tolerance buffer. This intermediary structure absorbs variations in solder ball parameters, significantly reducing the manufacturing precision requirements while maintaining reliability.
Solution Approach 2:
The patent changes the system's approach by introducing a new parameter - the resist layer protrusion height and shape - that directly controls short-circuit prevention. This shifts the critical control parameter from solder ball volume/shape to resist layer geometry, which can be more easily controlled and compensated for during manufacturing, thereby reducing overall process complexity.
3Reliability
If die and substrate alignment is made highly precise to prevent short-circuits, then connection reliability improves, but manufacturing cost and time increase due to stringent alignment requirements
Solution Approach 1:
The resist layer is applied in advance to create pre-defined protrusions that serve as alignment guides and tolerance buffers. These pre-formed structures compensate for alignment errors, allowing the bonding process to proceed successfully even with moderate alignment precision. This eliminates the need for time-consuming high-precision alignment adjustments during the bonding process.
Solution Approach 2:
The resist layer acts as an intermediary that decouples alignment precision from connection reliability. By providing a physical buffer and dam structure, the resist layer allows for larger alignment tolerances while still preventing short-circuits. This intermediary absorbs the misalignment errors, significantly reducing the time required for alignment operations.
Data Source
AI summary
A printed circuit board including: an insulating layer; a wiring layer disposed on an outermost side of the insulating layer and including a first pad and a first pattern; a first post disposed on the first pattern; and a resist layer disposed on the insulating layer and covering the wiring layer and the first post, wherein the resist layer may have a first protrusion in a region covering the first post and may have a first opening exposing the first pad from the resist layer.