Solder Preform Manufacturing with Premixed Master Alloy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solder preforms produced by conventional methods either fail to achieve strong metallic bonding between metal particles and solder due to mechanical embedding, or result in insufficient solder clearance and weak bonding strength due to particle dissolution in molten solder during the melting process.
Innovation Solution
A process involving the preparation of a premixed master alloy with high-melting metal particles dispersed in solder, where the particles are added to molten solder for a short duration to minimize dissolution, followed by casting and shaping into a solder preform, ensuring uniform dispersion and maintaining particle size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal particles are mechanically embedded in solder sheet by pressing method, then metal particles are present in solder preform, but metal particles are not wet by solder and metallic bonding is not achieved
Solution Approach 1:
The invention utilizes the phase transition of solder from solid to liquid state during heating. Metal particles are mechanically mixed with solid solder powder, then the mixture is heated to melt the solder, allowing liquid solder to wet the metal particles and form metallic bonds. This resolves the contradiction by using phase change to achieve bonding that cannot be obtained through mechanical pressing alone.
Solution Approach 2:
The invention performs preliminary mechanical mixing of metal particles with solder powder before melting. This preliminary distribution ensures uniform dispersion of metal particles throughout the solder matrix, which then facilitates effective wetting and bonding when the solder melts. This preliminary action prevents particle aggregation and ensures reliable metallic bonding.
2Stability of the object's composition
If metal particles are added to molten solder for prolonged stirring, then uniform dispersion is achieved, but metal particles dissolve into molten solder and particle size decreases
Solution Approach 1:
The invention performs preliminary mechanical mixing of metal particles with solid solder powder before melting. This preliminary distribution achieves uniform dispersion without requiring prolonged stirring in the molten state, thereby preventing particle dissolution. The uniform distribution is locked in during the melting process rather than being achieved through extended stirring.
Solution Approach 2:
The invention minimizes the time that metal particles are exposed to molten solder by rapidly completing the melting and casting process. Instead of prolonged stirring that would cause dissolution, the process quickly transitions from mixing to melting to casting, rushing through the molten state phase to prevent particle size reduction while still achieving uniform dispersion.
3Reliability
If solder preform is heated in reducing atmosphere, then oxides are removed and wetting is enabled, but metal particles may dissolve in molten solder
Solution Approach 1:
The invention performs preliminary mechanical mixing of metal particles with solid solder powder before heating. This preliminary distribution ensures uniform dispersion is achieved in the solid state, eliminating the need for prolonged stirring during heating that would cause particle dissolution in the reducing atmosphere. The uniform distribution is established before oxide removal and wetting processes begin.
Solution Approach 2:
The invention utilizes the phase transition from solid to liquid state to achieve both oxide removal and particle dispersion simultaneously. As solder melts in the reducing atmosphere, oxides are removed and liquid solder wets metal particles, achieving bonding without requiring prolonged stirring that would cause dissolution. The phase transition enables multiple functions in a single process step.
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 process ensures uniform dispersion of metal particles with maintained particle size, achieving strong metallic bonding and sufficient solder clearance for enhanced bonding strength between soldered portions.
Implementation Method 1
putting the premixed master alloy into molten solder such that the amount of the high-melting metal particles is 0.1-3 mass percent based on the molten solder followed by stirring
Implementation Method 2
casting the molten solder having a prescribed amount of the metal particles mixed therein into a mold to form a billet
Implementation Method 3
subjecting the billet to working into the form of a solder sheet and then shaping into the form of a solder preform having a predetermined shape
Implementation Method 4
the hydrogen reduces and removes oxides formed on the surface of the workpiece and the solder preform and enables them to be wet by molten solder
Implementation Method 5
the hydrogen reduces and removes oxides formed on the surface of the workpiece and the solder preform and enables them to be wet by molten solder
Implementation Method 6
as the solder preform melts, the molten solder may sometimes be protruded from the area between the portions being soldered
Data Source
AI summary
[Problems] A conventional process for producing a solder preform in which a predetermined amount of high-melting metal particles are directly put into molten solder and stirred, requires a long time for dispersing the high-melting metal particles by stirring. Therefore, in the conventional method for producing a solder preform, dissolution of the high-melting metal particles into the molten solder occurred during stirring, and their particle diameters became small. If a semiconductor chip and a substrate are soldered with a solder preform containing metal particles having such decreased diameters, the space between portions being soldered becomes narrow, and a sufficient bonding strength is not obtained.[Means for Solving the Problems] In the present invention, a premixed master alloy having a higher proportion of the high-melting metal particles in solder is first prepared, then the premixed master alloy is put into molten solder to disperse the high-melting metal particles. As a result, the high-melting metal particles can be uniformly dispersed in solder in a short length of time. Accordingly, a solder preform which is obtained by the process for producing a solder preform according to the present invention can maintain a predetermined clearance between portions being soldered, and a sufficient bonding strength is obtained.