Conductive Paste Composition for Direct PCB Soldering
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Solution Overview
Problem
Conventional printed circuit boards face issues with copper oxidation, leading to unreliable solder joints and environmental concerns associated with complex nickel or gold electroplating processes.
Innovation Solution
A conductive paste is developed, comprising a base resin mixture of epoxy resin and polyurethane, with a weight percentage of epoxy resin greater than or equal to 50%, along with a conductive filler, solvent, curing agent, and auxiliary agents, which allows for direct soldering with solder paste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper layer is used in conventional printed circuit board, then good conductivity is achieved, but the copper layer is easily oxidized which inhibits wetting effect of solder paste and reduces soldering reliability
Solution Approach 1:
The patent uses a composite resin system combining epoxy resin and polyurethane in a specific weight ratio (epoxy resin ≥50% of base resin). This composite material provides both oxidation resistance and good wetting effect for solder paste, eliminating the need for copper layers and their associated oxidation problems.
Solution Approach 2:
The patent modifies the chemical composition parameters of the conductive paste by specifying the weight percentage of epoxy resin in the base resin (≥50%), the molecular weight of epoxy resin (>10000 g/mol), and the epoxide equivalent (>5000 g/eq). These parameter changes ensure the material has sufficient oxidation resistance while maintaining good solderability.
2Reliability
If nickel or gold electroplating is applied to prevent copper oxidation, then soldering reliability is improved, but the process becomes complicated and causes environmental pollution
Solution Approach 1:
The patent extracts and eliminates the complex electroplating process entirely by using a resin-based conductive paste that inherently provides both conductivity and oxidation resistance. This removes the need for multiple plating layers (nickel and gold) and simplifies the manufacturing process while maintaining soldering reliability.
Solution Approach 2:
The patent replaces expensive electroplating materials (nickel and gold) with a cost-effective resin-based conductive paste containing conductive fillers. This alternative material provides the necessary functionality without the high cost and environmental burden of precious metal plating.
3Ease of manufacture
If low-temperature curing conductive paste is used instead of copper, then manufacturing complexity is reduced, but the paste cannot be soldered directly by solder paste
Solution Approach 1:
The patent changes the chemical composition parameters of the conductive paste by using epoxy resin with specific properties (molecular weight >10000 g/mol, epoxide equivalent >5000 g/eq) and controlling its weight percentage in the base resin (≥50%). These parameter changes enable the paste to cure at low temperatures while maintaining good wetting effect for direct soldering, thus achieving both ease of manufacture and solderability.
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 provides reliable soldering with good acid and alkali resistance, temperature stability, and flexibility, preventing tin immersion and ensuring stable adhesion and conductivity.
Implementation Method 1
epoxy resin has good acid and alkali resistance and corrosion resistance, and can withstand erosion or corrosion of flux components in the solder paste
Implementation Method 2
Epoxy resin has good temperature resistance and can withstand a soldering temperature of the solder paste
Implementation Method 3
the conducting circuit has a good wetting effect on the solder paste, and after soldering, adhesion and stability between materials are good
Implementation Method 4
the polyurethane is flexible and cushions stress between a base material and the conductive paste during the soldering, increasing the flexibility of the conducting circuit
Implementation Method 5
The conductive paste includes: a base resin, a solvent, a conductive filler, a curing agent, and an auxiliary agent
Data Source
AI summary
The present application provides a conductive paste and an electronic device, and relates to the technical field of function materials. The conductive paste according to the present application includes: a base resin, a solvent, a conductive filler, a curing agent, and an auxiliary agent. The base resin is a mixture of epoxy resin and polyurethane, a weight percentage of the epoxy resin in the base resin is greater than or equal to 50%, and the epoxy resin limits the polyurethane in a structure formed by curing of the base resin. According to the technical solution of the present application, soldering can be performed directly by solder paste, and good flexibility is brought.