Substrate Land Cutouts for LED Positioning Accuracy
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Solution Overview
Problem
Conventional planar illumination devices face issues with positional shifts of light sources due to solder flow during the reflow process, leading to inaccurate mounting positions of LEDs relative to the light guide plate.
Innovation Solution
The substrate features land portions with cutouts that match the shape of the terminals, restricting solder flow and ensuring self-alignment of the bonding surface, thereby maintaining the intended position of the LED during the reflow process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solder is applied to bond the light source to the substrate, then electrical connection and mechanical bonding are achieved, but the bonding surface position shifts due to solder flow during reflow process
Solution Approach 1:
The land portion is segmented by providing cutouts that divide the continuous solder flow path into separate regions. Each cutout creates an independent bonding zone that prevents solder from flowing across the entire land portion, thereby maintaining precise bonding surface positioning while still achieving adequate bonding strength through distributed solder joints.
Solution Approach 2:
Material (the cutout portions) is extracted from the land portion to create barriers that stop solder flow. By removing material in strategic locations, the patent prevents unwanted solder migration while preserving the essential bonding function in the remaining land area.
2Reliability
If the light source mounting position is adjusted to compensate for solder flow, then bonding reliability is improved, but the position of the light source with respect to the light guide plate becomes inaccurate
Solution Approach 1:
The cutouts are pre-formed on the land portion before the soldering process. This preliminary structural preparation creates built-in barriers that automatically control solder flow during reflow, eliminating the need for post-soldering position adjustments and ensuring both bonding reliability and positioning accuracy are achieved simultaneously.
Solution Approach 2:
The land portion structure itself provides the solution to solder flow control through its cutout features. The structure is self-regulating, where the geometry of the land portion with cutouts automatically limits solder migration without requiring external control mechanisms or additional processing steps to maintain positioning 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
This approach allows for precise definition and maintenance of the LED mounting position, reducing positional shifts and enhancing the accuracy of the light source placement within the planar illumination device.
Implementation Method 1
each of the land portions having a cutout provided by cutting in accordance with a shape of the corresponding terminal
Data Source
AI summary
A substrate according to an embodiment includes a plurality of land portions that are bonded to a plurality of terminals of a light source via solder, respectively, the light source having the terminals on a surface other than a light-emitting surface, each of the land portions having a cutout provided by cutting in accordance with a shape of the corresponding terminal.