Through-Hole Conductive Paste Joining for Low-Resistance Circuit Substrates
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Solution Overview
Problem
Conventional circuit substrates for LEDs face challenges in achieving high reliability and low resistance values due to issues with void formation and connection stability, particularly when using non-compressible porous substrates and electrically conductive pastes that can deform under heat and pressure.
Innovation Solution
A method of manufacturing a circuit substrate involving the formation of through-holes in an insulating substrate with Cu-based circuit patterns, filling these holes with a melting-point shift electrically conductive paste containing Sn-Bi solder powder and Cu powder, and performing pressure and heat treatment to form a Cu-Sn alloy, ensuring a dense and stable interlayer connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-compressible porous substrates and electrically conductive pastes are used, then manufacturing is simpler, but connection reliability deteriorates due to void formation and paste deformation under heat and pressure
Solution Approach 1:
The patent changes the physical state parameters of the electrically conductive paste by using a melting-point shift type paste that transitions from solid to liquid and back to solid during heating. This parameter change allows the paste to flow and fill voids during reflow soldering, then solidify to form strong connections, resolving the contradiction between connection reliability and manufacturing simplicity
Solution Approach 2:
The patent employs a composite material system consisting of melting-point shift type electrically conductive paste (containing Sn-Bi solder powder and Cu powder), resin, and circuit patterns. This composite approach combines materials with different properties to achieve both reliable connections and ease of manufacture, as the resin provides structural support while the solder powder ensures electrical conductivity and void elimination
2Reliability
If high current flow is required, then resistance values must be reduced, but this increases heat generation and requires more robust (less flexible) substrate structures
Solution Approach 1:
The patent applies local quality by creating dense, low-resistance connections only at the through-hole regions where current flow is needed, while the rest of the substrate maintains its flexibility. The melting-point shift paste forms localized high-conductivity paths without requiring the entire substrate to be rigid, thus resolving the contradiction between current flow capability and substrate flexibility
Solution Approach 2:
The patent utilizes parameter changes in the electrically conductive paste during heating to achieve low resistance values. The melting-point shift type paste undergoes phase transition that enables it to flow into the through-holes and form dense connections, reducing resistance locally without compromising the overall substrate flexibility
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 enhances connection reliability and reduces resistance values, allowing for the efficient flow of large currents while maintaining substrate flexibility and stability, addressing the limitations of previous technologies.
Implementation Method 1
performing heat treatment on the insulating substrate whose protrusion is subjected to the pressure treatment and causing the circuit patterns and the electrically conductive paste to be electrically connected with each other
Implementation Method 2
forming a Cu-Sn alloy
Implementation Method 3
an electrically conductive paste that is a melting-point shift electrically conductive paste including Sn—Bi solder powder, Cu powder, and resin
Data Source
AI summary
A method of manufacturing a circuit substrate includes forming, in an insulating substrate and circuit patterns that are provided on a first surface and a second surface of the insulating substrate, a through-hole penetrating the insulating substrate and the circuit patterns, where the circuit patterns contain Cu as a main component. The method includes filling, in the through-hole, an electrically conductive paste that is a melting-point shift electrically conductive paste including Sn—Bi solder powder, Cu powder, and resin, and forming a protrusion obtained by causing the electrically conductive paste to protrude from the through-hole. The method further includes performing pressure treatment on the protrusion near the through-hole; and performing heat treatment on the insulating substrate whose protrusion is subjected to the pressure treatment and causing the circuit patterns and the electrically conductive paste to be electrically connected with each other.