Conductive Paste for Direct Soldering on Copper PCBs
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Solution Overview
Problem
Conventional printed circuit boards face issues with oxidation of copper layers, leading to unreliable solder joints and increased risk of electrical component detachment, and low-temperature cured conductive pastes fail to achieve direct soldering with soldering tin wire.
Innovation Solution
A conductive paste comprising 5%-20% resin, 5%-20% solvent, and 70%-90% conductive filler, including a first filler to increase filling amount, a second filler to reduce sintering temperature, and a third filler to slow corrosion during soldering, allowing direct soldering with soldering tin wire without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper layer is used on printed circuit board, then electrical conductivity is improved, but oxidation resistance deteriorates leading to unreliable solder joints
Solution Approach 1:
The patent uses a composite conductive paste containing multiple types of conductive fillers (silver powder, copper powder, nickel powder) combined with specific resin and solvent systems. This composite formulation creates a multi-component material that achieves both electrical conductivity and oxidation resistance, resolving the contradiction between using pure copper for conductivity versus needing protection from oxidation.
Solution Approach 2:
The patent modifies the chemical composition parameters of the conductive paste by controlling the ratios of different metal powders (silver, copper, nickel), resin types, and solvent content. By adjusting these parameters, the paste achieves optimal balance between conductivity, solderability, and oxidation resistance without requiring additional plating processes.
2Reliability
If nickel or gold plating is applied to copper layer, then soldering reliability is improved, but process complexity increases and environmental contamination occurs
Solution Approach 1:
The patent extracts the protective and solderable surface layer function from the traditional multi-layer plating structure (copper base + nickel/gold plating) and integrates it directly into the conductive paste formulation. The paste itself contains metals with appropriate surface properties for soldering, eliminating the need for separate plating processes and reducing overall system complexity.
Solution Approach 2:
The conductive paste is designed to perform multiple functions simultaneously: providing electrical conductivity, ensuring oxidation resistance, enabling direct soldering, and serving as the structural basis for the conductive wiring. This multi-functional material replaces the traditional multi-step process involving separate copper deposition, plating, and soldering operations.
3Ease of manufacture
If low temperature cured conductive paste is used, then manufacturing ease is improved, but direct soldering capability deteriorates
Solution Approach 1:
The patent carefully controls the curing temperature parameter and the composition of the conductive filler metals. By selecting appropriate metal powders with suitable melting points and reactivity characteristics, and by optimizing the resin-curing temperature match, the paste can be cured at relatively low temperatures while still maintaining the ability to be directly soldered with tin wire, thus resolving the contradiction between easy manufacturing and soldering capability.
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 conductive paste enables reliable and efficient soldering with soldering tin wire, enhancing electrical properties and reducing corrosion risks, thus improving the reliability of solder joints and assembly processes.
Implementation Method 1
the second conductive filler is configured to reduce a sintering temperature of the conductive filler
Implementation Method 2
a velocity v1 of alloying the first conductive filler with tin, a velocity v2 of alloying the second conductive filler with tin, and a velocity v3 of alloying the third conductive filler with tin
Data Source
AI summary
The present application provides a conductive paste and an electronic device and relates to a technical field of new material. The conductive paste provided by the present application includes, 5%-20% by weight of a resin, 5%-20% by weight of a solvent, and 70%-90% by weight of a conductive filler; the conductive filler includes a first conductive filler, a second conductive filler, and a third conductive filler, and the first conductive filler is configured to increase a filling amount of the conductive filler, the second conductive filler is configured to reduce a sintering temperature of the conductive filler, and the third conductive filler is configured to slow erosion to the conductive filler by a soldering tin during a soldering process. By adopting the technical solution of the present application, soldering can be performed directly with soldering tin wire.