LED Light Bar PCB Extension Lines for SMT Alignment
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Solution Overview
Problem
The alignment precision of LEDs in the vertical direction of backlight modules is compromised due to surface tension issues during the surface mounting technology (SMT) process, where molten solder distributes unevenly over exposed signal lines and extension lines, causing LEDs to deviate from their intended positions on soldering pads.
Innovation Solution
Incorporating extension lines and signal lines on the printed circuit board (PCB) with a protective solder mask layer that exposes equal lengths and widths of these lines to balance surface tension, ensuring precise alignment of LEDs by maintaining equal exposed metal areas around the soldering pads, thereby stabilizing the LEDs' position during the SMT process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the quantity of LEDs is decreased to reduce manufacture cost, then the manufacture cost is reduced, but the gap between two adjacent LEDs becomes larger, making optical design and assembling precision more challenging
Solution Approach 1:
The patent applies preliminary action by pre-designing extension lines that extend beyond the soldering pad boundaries on the PCB. These extension lines are prepared in advance to balance surface tension during the SMT process, preventing solder from spreading unevenly and ensuring LEDs are soldered at precise positions despite larger gaps between them.
2Reliability
If the protective layer covers the signal lines completely, then the electrical insulation is improved, but the exposed metal areas are reduced, causing molten solder to distribute unevenly and LEDs to deviate from original positions
Solution Approach 1:
The patent applies local quality by creating a non-uniform protective layer configuration: the protective layer covers most signal lines for insulation, but intentionally leaves extension lines exposed beyond the soldering pad boundaries. This localized exposure provides controlled metal areas for solder distribution, balancing both electrical insulation and positioning accuracy requirements.
Solution Approach 2:
The extension lines serve as an intermediary element between the covered signal lines and the soldering pads. They provide a controlled exposed metal area that mediates the interaction between molten solder and the PCB, guiding solder distribution to maintain LED alignment precision while the majority of signal lines remain covered for insulation.
3Ease of manufacture
If the extension lines have unequal exposed lengths or widths, then the manufacturing process is simpler, but the surface tension is unbalanced, causing LEDs to deviate from vertical alignment
Solution Approach 1:
The patent applies asymmetry in a controlled manner: while the extension lines are symmetric in their exposure beyond the soldering pad, the asymmetric extension beyond the original signal line boundaries creates the necessary exposed metal areas. This controlled asymmetric design balances surface tension forces during soldering, ensuring LEDs maintain vertical alignment precision.
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 solution effectively balances surface tension, allowing for precise alignment and positioning of LEDs in the vertical direction, enhancing the optical design and assembly precision of backlight modules by maintaining equal exposed metal areas around the soldering pads.
Implementation Method 1
portions of the signal lines connected and adjacent to the soldering pads are exposed without being covered by the solder mask layer of the PCB, the molten solder will be easily distributed fully on the exposed areas due to its surface tension property
Data Source
AI summary
A light-emitting diode light bar includes a printed circuit board and a light-emitting diode. The printed circuit board has a protective layer, a first signal line, and a first extension line. The LED is disposed on the first signal line and the first extension line. The protective layer is formed above the first signal line and the first extension line, and has an opening that exposes a portion of the first signal line, and a portion of the extension line, such that a first exposed length of the first signal line is substantially equal to a second exposed length of the first extension line.