VCSEL Bonding Structure to Prevent Solder-Induced Peeling
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Solution Overview
Problem
The peeling of bonding portions between VCSEL chip substrates due to solder entering cracks or gaps, especially in the small pad areas of mesa-structured light emitting elements, is a significant issue in surface emitting laser devices.
Innovation Solution
A light emitting device configuration that includes a first substrate with a light emitting element, a second substrate bonded to its opposite surface, and a layered structure of conductive layers with an insulating layer covering the end portions of the conductive layers to prevent solder entry and peeling, ensuring secure bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solder is formed on the pad electrode to bond the VCSEL chip to the LDD substrate, then bonding strength is achieved, but solder enters cracks or gaps and causes peeling of the pad electrode or reflection electrode
Solution Approach 1:
An insulating layer is introduced as an intermediary between the solder and the conductive layers (pad electrode and reflection electrode). This insulating layer covers the end surfaces of the conductive layers, preventing solder from entering cracks or gaps while still allowing the solder to bond to the exposed pad surface, thus resolving the contradiction between bonding strength and peeling resistance
Solution Approach 2:
The insulating layer is formed in advance on the end surfaces of the conductive layers before the solder bonding process. This preliminary protective action prevents the harmful effect of solder penetration into cracks or gaps before it can occur, thereby preventing peeling while maintaining bonding integrity
2Area of stationary object
If the pad area is reduced to achieve compact VCSEL chip design, then miniaturization is achieved, but peeling is more likely to occur due to smaller bonding area
Solution Approach 1:
The insulating layer is selectively applied to the end surfaces of the conductive layers where cracks or gaps are most likely to form and where solder penetration would cause peeling. This local protective measure addresses the specific vulnerability of small pad areas without affecting the overall compact design, thereby maintaining miniaturization while improving peeling resistance
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 configuration effectively prevents peeling of the bonding portions by covering the end surfaces of the conductive layers with an insulating layer, enhancing the bonding strength and reliability of the light emitting device.
Implementation Method 1
a second conductive layer that is laminated on the first conductive layer and reflects light emitted from the light emitting element to the opposite surface side
Data Source
AI summary
To prevent peeling of a bonding portion between a first substrate having a light emitting element and a second substrate such as an LDD substrate. A light emitting device includes: a first substrate having a light emitting element; and a second substrate bonded to a surface side opposite to a light emitting surface of the light emitting element, in which the first substrate includes: a first conductive layer laminated on the opposite surface side of the light emitting element; a second conductive layer that is laminated on the first conductive layer and reflects light emitted from the light emitting element to the opposite surface side; a third conductive layer laminated on the second conductive layer and bonded to the second substrate via a bonding member; and an insulating layer laminated on the third conductive layer so as to cover at least end portions of the second conductive layer and the third conductive layer laminated.