Heat Spreader Solder Block Processing for Laser Diodes
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Solution Overview
Problem
Conventional heat spreaders made of metal-containing materials face issues with solder creeping up along the side surfaces of semiconductor elements, leading to short-circuits and blockage of laser light flux in semiconductor lasers, especially when using high-flowability solders like paste-shaped or foil-shaped solders.
Innovation Solution
A heat spreader with a metal-containing substrate having a solder block processing on at least one side surface and adjacent region to inhibit solder flow, combined with a solder block layer of low wettability and flowability materials like Pt, Mo, Pd, or Cr, and an adhesion layer for improved connection and heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-flowability solders like paste-shaped or foil-shaped solders are used to improve solder joint quality, then solder wettability and connection reliability are improved, but solder creeps up along the side surfaces causing short-circuits and blocking laser light flux
Solution Approach 1:
The patent applies different surface treatments to different regions of the substrate. The side surface is treated with low wettability (solder block processing) to prevent solder creeping, while the upper surface maintains high wettability for good solder joint formation. This local differentiation of surface properties resolves the contradiction between preventing solder creeping and ensuring good solder connection.
Solution Approach 2:
The patent introduces an intermediary layer or surface treatment on the side surface that acts as a barrier between the solder and the substrate. This intermediary surface with low wettability prevents solder from creeping up along the side surfaces while allowing solder to properly adhere to the upper connection surface.
2Ease of manufacture
If conventional heat spreader materials like Si or ceramics are used to ease manufacturing and reduce cost, then ease of manufacture and cost are improved, but heat transfer characteristics deteriorate
Solution Approach 1:
The patent employs a composite substrate structure combining materials with different properties. The substrate integrates high thermal conductivity materials (such as metal-containing materials) to ensure excellent heat transfer characteristics, while maintaining manufacturability through appropriate material selection and processing techniques.
Solution Approach 2:
The patent changes the material parameters of the substrate by selecting materials with specific thermal conductivity, wettability, and mechanical properties. By adjusting these material parameters, the patent achieves both good heat transfer characteristics and manufacturability.
3Temperature
If metal-containing materials are used for the substrate to improve heat transfer, then heat transfer characteristics are improved, but solder wettability increases causing solder to creep up along side surfaces
Solution Approach 1:
The patent applies local quality differentiation by treating only the side surface with low wettability characteristics through solder block processing, while the bulk material maintains high thermal conductivity. This localized surface treatment prevents solder creeping on metal-containing substrates without compromising heat transfer.
Solution Approach 2:
The patent introduces a thin surface layer or coating on the side surface that provides low wettability to prevent solder creeping. This thin film approach allows the bulk metal-containing material to maintain excellent heat transfer while the surface layer controls solder behavior.
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
Prevents solder from creeping up to the semiconductor element, reducing defects and ensuring reliable heat transfer while maintaining high manufacturing productivity and cost-effectiveness.
Implementation Method 1
the side surface of the substrate is subjected to solder block processing for preventing solder from flowing
Implementation Method 2
transferring heat generated when the semiconductor element operates to the second-component through the heat spreader
Data Source
Figure 1~3
Figure 4~6
Figure 7~9
AI summary
The present invention provides a heat spreader 1 which includes a substrate 7 composed of a metal-containing material and in which a second-component connection surface 6 of the substrate 7 is provided with wettability with a solder and a solder block layer 14 is formed in at least one of respective regions, adjacent to each other, of the second-component connection surface 6 and a side surface 13. When a semiconductor device 4 is manufactured by connecting a semiconductor laser 2 to the element connection surface 5 through an element connecting layer 8, and then connecting a heat sink 3 to the second-component connection surface 6 through a second-component connecting layer 9 having a melting point lower than that of the element connecting layer 8, the semiconductor block layer 14 can inhibit the melted solder from creeping up along the side surface 13, which can prevent defects that the solder that has crept up short-circuits the semiconductor laser 2 and blocks a luminous flux of laser light emitted from an emission surface 12 of the semiconductor laser 2.