Metal Mesh Constraint for Uniform Solder Layer Height
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Solution Overview
Problem
Existing methods for pre-soldering metal surfaces on metallized substrates often result in unsatisfactory surfaces with bulging solder and significant thickness variations, leading to uneven heat conduction and potential component instability.
Innovation Solution
A method involving a flat, tensioned metal mesh made of a non-solder-wetting material, such as stainless steel, is pressed onto solder preforms during soldering to achieve a uniform solder layer height and minimize pore formation, ensuring even thickness and predictability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solder preforms are melted without a metal mesh, then the solder forms a clear meniscus edge angle, but the solder layer becomes uneven with bulging and thickness variations
Solution Approach 1:
A metal mesh is introduced as an intermediary tool between the solder preform and the substrate. The mesh acts as a temporary form-giving element during melting, constraining the solder to achieve uniform thickness without the usual meniscus bulge. After cooling, the mesh is removed, leaving a flat solder layer with thickness variation less than 20 μm.
Solution Approach 2:
The invention changes the physical state and constraints during the soldering process by applying a metal mesh structure. This external constraint modifies the melting behavior of the solder, preventing capillary rise and meniscus formation, and achieving a flat top surface with controlled thickness.
2Reliability
If thicker solder layers are produced to ensure adequate coverage, then component placement stability improves, but thickness variations and pore formation increase
Solution Approach 1:
The metal mesh serves as a form-giving intermediary that enables production of thicker solder layers (up to 100 μm) with uniform thickness. The mesh structure confines the molten solder, preventing lateral flow and bulging, while allowing adequate thickness for reliable component attachment.
Solution Approach 2:
The metal mesh itself is a porous structure that allows gas escape during melting while maintaining the form-giving function. The openings in the mesh permit trapped gases to escape, reducing pore formation in the solidified solder layer while the mesh wires maintain the uniform thickness profile.
3Manufacturing precision
If gas escapes during soldering, then pore formation is reduced, but gas bubbles may form on the solder surface
Solution Approach 1:
The metal mesh's porous structure with controlled opening sizes provides escape paths for gases generated during solder melting. The porosity allows gas to pass through the mesh and escape from the solder layer, minimizing pore formation while the mesh structure prevents gas from coalescing into large surface bubbles.
Solution Approach 2:
The metal mesh creates local quality differences in the solder layer - areas under the mesh wires have constrained solder flow while areas through the openings allow gas escape. This local differentiation enables simultaneous pore minimization and bubble prevention.
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 solution achieves a uniform solder layer with thickness variations of less than 20 μm, preventing bulging and enhancing even heat conduction from components to substrates, allowing for stable and predictable component placement.
Implementation Method 1
the metal mesh consists of a material that does not wet the solder
Implementation Method 2
Heat conduction from the component to the substrate becomes more even and predictable
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for pre-soldering metal surfaces onto metallised substrates (1a, 1b), wherein solder preforms (2a, 2b) are placed onto the metal surfaces of the substrates (1a, 1b) or vice versa, after which the solder preforms (2a, 2b) are fused. To achieve a defined, consistent height of the solder layer, inhibit the formation of bulged solder, enable the production of even thicker solder layers of around 100 μm with a thickness fluctuation of below 20 μm to the edge of the solder layer and minimise a pore formation in the solder layer, the invention proposes pressing a metallic gauze (3a, 3b) flat onto the solder preforms (2a, 2b) during the soldering or fusing processes, the metallic gauze (3a, 3b) consisting of a solder-wetting material.