Circuit Board Pad Structure for Repeatable LED Re-Soldering
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Solution Overview
Problem
Existing display technologies using mini LEDs and micro LEDs face challenges in maintainability and yield rates due to damage to circuit board pads during component removal, leading to low repairability and efficiency.
Innovation Solution
A circuit board design featuring multiple conductive layers with stop layers and anti-oxidation layers that form intermetallic compounds with solder, allowing for reliable re-soldering of electronic components, and a reflective layer for component fixation, enhancing maintainability and yield rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional circuit board design without stop layers is used, then manufacturing process is simple, but solder joint reliability deteriorates due to oxidation and poor re-soldering capability
Solution Approach 1:
The conductive layer is segmented into multiple functional sub-layers: main conductive layer for electrical connection, stop layer for oxidation prevention and reaction control, and anti-oxidation layer for surface protection. This segmentation allows each layer to perform its specific function optimally, improving solder joint reliability while managing complexity through functional decomposition.
Solution Approach 2:
The circuit board employs a composite conductive layer structure combining different materials with complementary properties: copper or copper alloy for main conductivity, nickel or nickel alloy for oxidation resistance and controlled reaction, and tin or tin alloy for solderability. This composite structure achieves superior solder joint reliability by leveraging the strengths of each material.
2Illumination intensity
If mini LEDs and micro LEDs are used to improve display effect, then picture contrast reaches OLED level, but maintainability deteriorates due to pad damage during component removal
Solution Approach 1:
The stop layer and anti-oxidation layer are applied beforehand to the conductive layer to create a protective barrier against oxidation and excessive solder reaction. This pre-protection ensures that even when components are removed and re-soldered multiple times, the pad structure remains intact and reusable, significantly improving maintainability of high-precision displays.
Solution Approach 2:
The invention changes the chemical and physical parameters of the conductive layer by introducing layers with controlled thickness (100-5000 Å for stop layer, 100-40000 Å for anti-oxidation layer) and specific material compositions. These parameter changes enable the layer to resist oxidation and control solder reaction rates, allowing repeated component removal and re-soldering without pad damage.
3Ease of repair
If multiple conductive layers with stop layers are added, then re-soldering capability is improved, but manufacturing complexity increases
Solution Approach 1:
The stop layer and anti-oxidation layer are applied locally to the conductive layer regions that require soldering, rather than uniformly across the entire circuit board. This localized application improves re-soldering capability where needed while minimizing additional manufacturing complexity in non-critical areas.
Solution Approach 2:
The stop layer and anti-oxidation layer are formed as preliminary steps during the circuit board manufacturing process, before component mounting and soldering. This preliminary action integrates the protective layers into the base manufacturing flow, reducing the need for separate post-processing steps and minimizing overall manufacturing complexity.
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 design improves maintainability and yield rates by ensuring reliable soldering connections and protecting against oxidation, enabling repeated repairs and reducing component damage during maintenance.
Implementation Method 1
The main conductive layer is configured to be capable of creating a first intermetallic compound with solder
Implementation Method 2
the stop layer is configured to be capable of creating a second intermetallic compound with the solder
Implementation Method 3
the anti-oxidation layer is configured to be capable of creating a third intermetallic compound with the solder
Implementation Method 4
an anti-oxidation layer... configured to be capable of creating a third intermetallic compound with the solder
Data Source
AI summary
A circuit board includes a substrate, a first conductive layer, a first insulating layer and a second conductive layer. The first conductive layer includes a plurality of first conductive portions. The second conductive layer includes a plurality of second conductive portions. A second conductive portion passes through a first via hole in the first insulating layer to be in electrical contact with a first conductive portion. The first conductive layer and the second conductive layer each include at least one main conductive layer, which is capable of creating a first intermetallic compound with solder. At least one of the first conductive layer and the second conductive layer further includes a stop layer capable of creating a second intermetallic compound with the solder. A rate of a reaction between the stop layer and the solder is lower than a rate of a reaction between the main conductive layer and the solder.