Thermosetting Resin Solder Paste Mounting Structure
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Solution Overview
Problem
Conventional mounting structures using low-melting-temperature lead-free solders face issues with solder flush during reflow treatments, leading to potential short circuits and reliability concerns, especially when components are mounted on both surfaces of a circuit substrate.
Innovation Solution
A mounting structure and method that utilize a solder paste with a low-setting temperature thermosetting resin, where the resin covers only a portion of the solder, preventing solder flush by allowing the solder to spread and return to its original position during reflow, and ensuring the resin does not contact the bumps, thereby maintaining structural integrity and impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If low-melting-temperature Pb-free solder (Sn-Zn, Sn-Ag-In, or Sn-Bi) is used to replace high-melting-point Sn-Ag-Cu solder, then the reflow temperature can be reduced to avoid damaging components, but the connection reliability in the soldered connection parts becomes unclear and solder flush occurs during reflow treatment
Solution Approach 1:
The patent uses a composite material consisting of low-melting-point Sn-Bi solder mixed with a thermosetting resin (such as epoxy resin) to form a solder paste. This composite structure allows the solder to provide low-temperature joining while the resin provides structural support and prevents solder flush during reflow treatment, thereby resolving the contradiction between reduced reflow temperature and maintained connection reliability
Solution Approach 2:
The thermosetting resin acts as an intermediary material that bridges the solder and the substrate. The resin covers the periphery of the solder bump and provides mechanical support during the reflow process, preventing the solder from flushing out while still allowing the solder to form reliable electrical and mechanical connections between components
2Strength
If the resin in the solder paste covers the entire periphery of the solder, then the strength of the solder is reinforced, but solder flush occurs when the solder is melted again during the second heat treatment
Solution Approach 1:
The patent applies local quality by having the resin cover only the peripheral region of the solder bump rather than the entire surface. This localized coverage provides structural reinforcement at the critical periphery where solder flush occurs, while leaving the central solder material exposed to allow controlled spreading and return during reflow treatment
3Adaptability or versatility
If components are mounted on both surfaces of a circuit substrate, then the functionality and integration are enhanced, but the productivity is significantly low due to separate spot soldering steps
Solution Approach 1:
The patent merges the soldering process for both surfaces into a single reflow treatment step. By using the thermosetting resin-containing solder paste on both surfaces, both front and back side components can be soldered simultaneously in one heating cycle, eliminating the need for separate spot soldering steps and significantly improving productivity while maintaining the ability to mount components on both surfaces
4Strength
If the resin covers the entire surface of the solder part, then the impact resistance is enhanced, but the solder cannot spread and return to its original position during reflow, causing solder flush
Solution Approach 1:
The patent implements local quality by restricting resin coverage to the periphery of the solder bump while leaving the central area exposed. This allows the solder in the central region to spread and return to its original position during reflow treatment, maintaining soldering functionality, while the peripheral resin provides the necessary impact resistance and structural support
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 effectively prevents solder flush defects, enhances impact resistance, and maintains reliable connections between components and the circuit substrate, even under thermal or mechanical stress, without the complexity of using different solder pastes or temporal fixing processes.
Implementation Method 1
a solder paste using a thermosetting resin as a flux has been proposed in order to enhance reliability in the impact resistance in connection parts
Implementation Method 2
the resulting material is subjected to reflow heating in the heating furnace 16 to cause a solder ingredient in the solder paste P to malt
Data Source
AI summary
A mounting structure, including: a first component that has a first bump; a second component that has a second bump; a mounting component that has a primary mounting surface and a secondary mounting surface; a first solder that connects an electrode on the primary mounting surface and the first bump; a second solder that connects an electrode on the secondary mounting surface and the second bump; and a reinforcing resin that covers a part of the first solder and that is not in contact with the primary mounting surface.