Light-emitting device substrate with depressed portions for bonding strength
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Solution Overview
Problem
The bonding strength of small-sized light-emitting devices to mounting boards is insufficient, leading to potential defective mounting and reduced reliability.
Innovation Solution
A light-emitting device design featuring a substrate with depressed portions and metal films covered by a solder mask, which increases the volume of bonding members and prevents short circuits and delamination, ensuring stable mounting and improved bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the light-emitting device is downsized, then the device size is reduced, but the bonding strength to mounting boards becomes insufficient
Solution Approach 1:
The substrate is divided into a flat mounting surface and depressed portions, creating distinct functional zones. The depressed portions are segmented into multiple recesses that can accommodate bonding members of different sizes and shapes, allowing optimized bonding configuration independent of the overall device size reduction.
Solution Approach 2:
The invention transitions from a two-dimensional flat mounting surface to a three-dimensional structure with depressed portions. This vertical dimensionality change allows bonding members to be positioned at different depths and orientations, increasing the volume available for bonding material and improving bonding strength without increasing the device's planar footprint.
2Reliability
If metal films are exposed on the back surface, then electrical connectivity is achieved, but short circuits and delamination may occur
Solution Approach 1:
The solder mask is selectively applied to cover specific metal films in certain areas while leaving other metal films exposed in the depressed portions. This local differentiation allows electrical connectivity where needed while preventing short circuits and delamination in other areas, optimizing both functionality and reliability.
Solution Approach 2:
The solder mask acts as an intermediary protective layer between the metal films and the external environment. It prevents harmful effects such as oxidation, moisture ingress, and electrical shorting, while allowing controlled electrical connectivity through strategically exposed metal film regions in the depressed portions.
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 enhances the bonding strength and mountability of light-emitting devices, reducing defective mounting and improving heat dissipation and alignment stability.
Implementation Method 1
The covering member has light reflectivity. The covering member covers at least a part of a lateral surface of each of the plurality of light-emitting elements and at least a part of the front surface of the base.
Data Source
AI summary
A light-emitting device includes a substrate, a plurality of light-emitting elements aligned along a longitudinal direction, and a covering member. The substrate includes a pair of first depressed portions and a second depressed portion each opening on a back surface and a bottom surface of a base and positioned on both end sides of the base in the longitudinal direction. The second depressed portion has a width larger than a width of the first depressed portions as measured along a height direction. First metal films extend from inside the first depressed portions to the back surface. A second metal film extends from inside the second depressed portion to the back surface. A solder mask covers at least a part of each of the first metal films and at least a part of the second metal film on the back surface of the base.