Dual-PSR Circuit Board Layout 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 affects 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 interconnection visibility is prevented, but patterning for exposing pads becomes difficult and the pad open region is not clearly defined
Solution Approach 1:
The patent divides the solder resist into two separate layers: a first PSR layer that provides thickness to prevent interconnection visibility, and a second PSR layer that is patterned to clearly define the pad open region. This segmentation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
The second PSR layer is selectively removed only in the pad open region area, creating a localized opening that exposes the underlying interconnections. This local quality change allows the pad region to be clearly defined while the rest of the thick PSR structure remains intact to prevent interconnection visibility elsewhere.
2Manufacturing precision
If a thin PSR is used to clearly define pad open region, then patterning is easier, but interconnections are easily observed affecting black color display
Solution Approach 1:
The solder resist functionality is segmented into two layers: the first layer provides the necessary thickness to block interconnection visibility, while the second layer provides the patterned opening for pad definition. This resolves the contradiction by distributing functions across layers rather than relying on a single thin layer.
Solution Approach 2:
The patent uses a composite structure of two PSR layers with different characteristics. The first layer acts as a base layer for preventing visibility, while the second layer acts as a patterning layer for defining the pad open region, creating a composite material system that achieves both goals simultaneously.
3Measurement precision
If the pad open region is not clearly defined, then accurate arrangement of micro LEDs is difficult, but forming a thick PSR makes patterning difficult
Solution Approach 1:
The patterning process is segmented into two stages corresponding to two PSR layers. The first layer is formed with a general pattern, and the second layer provides the precise pad open region definition. This segmentation makes the overall patterning process more manageable and achieves higher arrangement accuracy.
Solution Approach 2:
The first PSR layer is formed in advance to establish the base structure and prevent interconnection visibility. This preliminary action creates a stable foundation that facilitates the subsequent formation of the second layer with precise pad openings, improving both manufacturability and arrangement accuracy.
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
The solution 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.