Solder Bump Formation Using Adhesion Control Layer
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Solution Overview
Problem
Existing methods for forming solder bumps on substrates using screen printing with photosensitive dry films require aggressive heat treatments and chemical agents for film removal, which can damage electronic structures.
Innovation Solution
A method involving an intermediate layer with low adhesion energy between the film and substrate allows for less aggressive film removal, using techniques like peeling or plasma etching, and includes a heat treatment step for solder bump formation and shaping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a photosensitive dry film is used for screen printing solder bumps, then the formation of large diameter solder bumps at low pitch is enabled, but aggressive heat treatment and chemical agents are required for film removal which can damage electronic structures
Solution Approach 1:
A release layer is introduced as an intermediary between the photosensitive dry film and the substrate. This release layer has controlled adhesion properties that allow the film to be easily removed after solder bump formation without requiring aggressive chemical agents or excessive heat, thereby protecting electronic structures on the substrate while maintaining the ability to form precise solder bumps.
2Strength
If heat treatment at temperature higher than 250°C is applied for solder bump formation, then solder bumps are properly formed and adhered, but the adhesion energy between the photosensitive film and substrate increases making film removal difficult and damaging
Solution Approach 1:
The release layer serves as a mediator that decouples the adhesion requirements. During heat treatment, the release layer protects the substrate-film interface from excessive adhesion bonding, allowing strong solder bump formation while maintaining easy film removability through the release layer's controlled adhesion properties.
Solution Approach 2:
The adhesion energy parameters of the release layer are specifically controlled to be lower than both the substrate-film and film-solder interfaces. This parameter differentiation allows the system to achieve strong solder adhesion through heat treatment while enabling easy film removal by targeting the weakest link (the release layer interface).
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
Enables the production of large diameter solder bumps with reduced risk of damaging the substrate or electronic structures, facilitating efficient assembly and mechanical cohesion between substrates.
Implementation Method 1
the intermediate layer being adapted to have an adhesion energy, at either of the interfaces formed with the first front face and the film, which is lower than the adhesion energy of an interface likely to be formed between the film and the first front face
Implementation Method 2
a step of heating at a temperature higher than their melting temperature (commonly called "Reflow"), providing said bumps with a truncated sphere shape. The "reflow" step enables in particular adhesion of solder bumps on the surface of which they are formed to be promoted, but also solder forming each of the bumps to be homogenised
Implementation Method 3
step d) is carried out by peeling or plasma etching
Data Source
AI summary
A serigraphy method for producing a soulder bump on the front surface of a substrate includes: forming a film on the front surface, forming an opening in the film, filling the opening with a souldering material, and removing the film. Forming a film on the front surface is preceded by the formation of an intermediate layer between the film and the front surface, the intermediate layer being adapted to exhibit a force of adherence at one and/or the other interface formed with the first front surface and the film lower than the force of adherence that can be formed between the film and the first front surface.