VCSEL Pad Bonding Structure for Precise Substrate Alignment
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Solution Overview
Problem
As VCSEL chips miniaturize, the smaller pads and closer pitch between light-emitting elements make it difficult to form bonding members accurately, leading to misalignment and potential short-circuiting issues when bonding substrates.
Innovation Solution
A light-emitting device with a first substrate having a conductive layer and bonding layer on its pad, bonded to a second substrate with a mesa-shaped light-emitting element, where the bonding layer includes multiple metal layers sandwiching a nickel layer, facilitating precise bonding without misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the VCSEL chip is miniaturized to reduce size and cost, then productivity and cost efficiency are improved, but the pad size becomes smaller and the pitch between light-emitting elements becomes smaller, making it difficult to form bonding members accurately and leading to misalignment and short-circuiting issues
Solution Approach 1:
The patent introduces a protrusion structure on the bonding pad that serves as a physical intermediary feature. This protrusion extends beyond the bonding pad surface, providing a larger target area for bonding member formation and placement. The protrusion acts as a mediator between the small pad and the bonding member, enabling accurate positioning and reliable bonding even when the overall device is miniaturized, thus resolving the contradiction between miniaturization and bonding precision
Solution Approach 2:
The protrusion structure is formed in advance on the bonding pad before the bonding process. This preliminary structural preparation ensures that when bonding members are subsequently formed or placed, they have a predetermined reference feature to align with, preventing misalignment issues that would otherwise occur with miniaturized pads. The protrusion is created as a pre-existing guide feature that facilitates accurate bonding member positioning
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 allows for accurate and reliable bonding between substrates, preventing short-circuiting and ensuring proper positioning of the bonding layer, enhancing the reliability of the light-emitting device.
Implementation Method 1
a bonding member such as solder is formed on a pad on an upper surface of a mesa-shaped light-emitting element formed in the VCSEL chip, and then the LDD substrate or the like is bonded thereto
Implementation Method 2
a first conductive layer disposed on the first pad; and a bonding layer disposed on the first conductive layer
Data Source
AI summary
Problems when a first pad on a first substrate for outputting a drive signal for driving a light-emitting element is bonded to a second pad on a second substrate having the light-emitting element are prevented. A light-emitting device includes a first substrate that outputs a drive signal for a light-emitting element, and a second substrate that is laminated on the first substrate and includes the light-emitting element. A first surface side of the first substrate includes a first pad that supplies the drive signal to the light-emitting element, a first conductive layer disposed on the first pad, and a bonding layer disposed on the first conductive layer, and a second surface side of the second substrate facing the first surface of the first substrate includes the light-emitting element having a mesa shape, and a second pad that is disposed on the light-emitting element and bonded to the first pad.