Dual-Layer Solder Resist Circuit Board for Clear Micro LED Pad Openings
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Solution Overview
Problem
Conventional micro LED displays face challenges in clearly defining pad open regions on circuit boards, leading to potential bonding failures and visibility of interconnections, which affect the display of desirable black colors.
Innovation Solution
A circuit board design featuring a first photosensitive solder resist (PSR) that defines a pad open region and a second thicker PSR with an opening larger than the pad open region, ensuring clear exposure and accurate placement of micro LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thick PSR is formed to prevent interconnections from being observed, then the visibility of interconnections is improved, but the patterning for exposing pads becomes difficult and the pad open region is not clearly defined
Solution Approach 1:
The solder resist is divided into two separate layers: a first PSR layer that provides thickness to mask interconnections, and a second PSR layer that enables clear definition of the pad open region through patterning. This segmentation allows each layer to perform its specific function without compromising the other.
Solution Approach 2:
The solution transitions from a single-layer PSR to a multi-layer PSR structure, adding a vertical dimension to the design. The first PSR layer addresses the thickness requirement for masking, while the second PSR layer addresses the patterning requirement for pad definition, effectively resolving the contradiction through dimensional expansion.
2Manufacturing precision
If a thin PSR is used to enable clear patterning of pad open region, then the manufacturing precision is improved, but the interconnections become easily observed
Solution Approach 1:
The functions of masking interconnections and defining pad open regions are segmented into two separate PSR layers. The first PSR layer (thicker) handles the masking function, while the second PSR layer (thinner with pattern) handles the pad definition function, allowing both requirements to be met simultaneously.
Solution Approach 2:
Different regions of the PSR structure have different thicknesses and properties. The first PSR layer provides local thickness for masking, while the second PSR layer provides local patterning for pad exposure, creating localized quality variations that satisfy different functional requirements in different areas.
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 design effectively prevents interconnection visibility while clearly defining pad open regions, reducing bonding failures and enhancing the display of black colors in micro LED displays.
Implementation Method 1
a first photosensitive solder resist (PSR) covering the interconnections and defining a pad open region exposing portions of the interconnections
Implementation Method 2
a second PSR covering the first PSR and having an opening exposing the pad open region
Data Source
AI summary
A circuit board includes a base having a plurality of interconnections on an upper surface thereof, a first photosensitive solder resist (PSR) covering the interconnections and defining a pad open region exposing portions of the interconnections, a second PSR covering the first PSR and having an opening exposing the pad open region. The opening of the second PSR is larger than the pad open region of the first PSR.