Electronic Module Soldering with Sequential Resin Curing
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Solution Overview
Problem
The challenge in manufacturing electronic modules is the risk of solder breakage due to thermal expansion and stress, which can occur when high-performance electronic components are mounted on wiring boards, leading to potential failures in bonding and reliability issues.
Innovation Solution
A method involving the use of a paste containing solder powder and uncured thermosetting resin, where a second uncured resin is applied to form a bonding portion that cures before heating, allowing the solder to melt and solidify without warping the components, and a separate resin portion is cured to reinforce the solder bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-performance electronic components are mounted on wiring boards with solder, then the electronic modules can be downsized and performance improved, but the solder may break due to thermal expansion stress and impact
Solution Approach 1:
An underfill resin is introduced as an intermediary material between the electronic component and wiring board. This underfill resin has a coefficient of thermal expansion that matches the electronic component, and it bonds to both the component and board, acting as a stress-absorbing intermediary that prevents direct stress transmission to the solder joints during thermal cycling and impact events.
Solution Approach 2:
The bonding structure uses a composite material system combining solder material and underfill resin material. The solder provides electrical and mechanical bonding, while the underfill resin provides stress absorption and environmental protection. This composite approach allows the system to leverage the complementary properties of different materials to simultaneously achieve strong bonding and stress resistance.
2Manufacturing precision
If paste containing solder powder and uncured thermosetting resin is heated to solder melting point, then the solder aggregates and bonds components, but the wiring board and/or electronic component may warp due to heating
Solution Approach 1:
The wiring board is pre-heated to a temperature close to the solder melting point before the actual reflow soldering process. This preliminary heating reduces the temperature differential between the board and the paste, minimizing thermal shock and preventing warpage during the soldering process while still allowing the solder to aggregate and bond properly.
Solution Approach 2:
The heating process parameters are optimized by controlling the peak temperature and dwell time. The maximum temperature is kept just sufficient to melt the solder (typically 10-20°C above melting point) and the heating rate is controlled to allow uniform heat distribution. This parameter optimization enables complete solder bonding while minimizing thermal expansion and warpage.
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 approach effectively disperses thermal stress and enhances the bonding strength between electronic components and wiring boards, preventing solder breakage and ensuring reliable electrical connections.
Implementation Method 1
curing the second resin to form a second resin portion that bonds the electronic component and the wiring board
Implementation Method 2
heating the paste to a temperature equal to or higher than a solder melting point after the second resin portion is formed, to melt the solder powder
Implementation Method 3
solidifying molten solder at a temperature lower than the solder melting point to form a solder portion that bonds the electronic component and the wiring board
Implementation Method 4
curing the first resin after the solder portion is formed, to form a first resin portion that is in contact with the solder portion
Data Source
AI summary
A method of manufacturing an electronic module includes supplying paste to an electronic component and/or a wiring board. The paste includes solder powder and first resin. The method includes supplying second resin to the electronic component and/or the wiring board. The method includes placing one of the electronic component and the wiring board on another. The method includes curing the second resin to form a second resin portion. The method includes heating the paste to a temperature equal to or higher than a solder melting point after the second resin portion is formed. The method includes solidifying molten solder at a temperature lower than the solder melting point to form a solder portion that bonds the electronic component and the wiring board. The method includes curing the first resin after the solder portion is formed, to form a first resin portion.