Copper Alloy Sheet for FPC Heat Dissipation and Bending
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Solution Overview
Problem
LEDs mounted on FPC boards experience thermal degradation due to insufficient heat dissipation, leading to shorter service life, and the use of aluminum sheets as heat sinks causes warping and rupture due to thermal expansion differences, while copper sheets soften under heat, losing shape integrity.
Innovation Solution
A copper alloy sheet with specific alloying elements (Ag, Cr, Fe, In, Ni, P, Si, Sn, Ti, Zn, Zr) is developed, offering excellent heat dissipation, workability in repetitive bending, and high heat resistance by controlling crystal orientation and maintaining tensile strength, with electrical conductivity above 60% IACS and a specific X-ray diffraction peak intensity ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aluminum sheet is laminated as heat sink to FPC board, then heat dissipation is improved, but warping and rupture occur due to thermal expansion difference
Solution Approach 1:
The invention changes the material parameters by selecting copper as the heat sink material instead of aluminum, specifically matching the coefficient of thermal expansion to that of the FPC board and copper wires. This parameter change eliminates the thermal expansion mismatch that causes warping and rupture, while maintaining effective heat dissipation capability.
Solution Approach 2:
The invention uses a composite structure consisting of a copper heat sink layer laminated to the FPC board. This composite material approach allows optimization of both thermal management properties and dimensional stability by combining copper's high thermal conductivity with its matched thermal expansion characteristics.
2Reliability
If copper sheet is used as heat sink, then thermal expansion mismatch problem is solved, but bending portions create cracks due to strain hardening
Solution Approach 1:
The invention applies local quality by creating a copper alloy composition specifically optimized for bending regions. The alloy contains controlled amounts of elements like Sn, Pb, or Zn that locally enhance ductility and reduce strain hardening in bending portions, while maintaining overall thermal conductivity and thermal expansion compatibility.
Solution Approach 2:
The invention changes the chemical composition parameters of the copper heat sink by adding specific alloying elements within defined ranges (e.g., 0.01-3.0 wt% Sn, 0.01-2.0 wt% Pb). These compositional changes modify the material's strain hardening characteristics to prevent crack formation during repetitive bending while preserving thermal performance.
3Temperature
If ordinary tough pitch copper is used, then heat dissipation is achieved, but shape is lost due to softening by heat
Solution Approach 1:
The invention changes the compositional parameters by adding small amounts of alloying elements (total 0.01-3.5 wt%) to the copper base. These compositional modifications increase the alloy's heat resistance and tempering characteristics, enabling it to maintain shape integrity at elevated temperatures while preserving adequate thermal conductivity for heat dissipation.
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 copper alloy sheet provides effective heat dissipation, maintains shape integrity under repetitive bending, and exhibits high heat resistance, ensuring prolonged service life and reliability in applications like in-vehicle lighting.
Implementation Method 1
heat dissipation of a resin used as a substrate is insufficient, resulting in a shorter service life
Implementation Method 2
difference between the coefficient of linear thermal expansion of an aluminum sheet and the coefficient of linear thermal expansion of a copper wire constituting a circuitry of an FPC board causes warping of the FPC board
Implementation Method 3
copper has a larger strain hardening coefficient than aluminum so that bending portions are likely to create cracks when an FPC board is formed in complex shapes
Implementation Method 4
a copper wire experiences tensile stress in repetitive expansion and contraction due to heat, resulting in rupture
Data Source
AI summary
Provided is a copper alloy plate that is for an FPC substrate and that has superior heat dissipation, repeated bending workability, shape retaining properties, and heat resistance. The copper alloy plate contains at least 0.01 mass % of the total of at least one element selected from the group consisting of Ag, Cr, Fe, In, Ni, P, Si, Sn, Ti, Zn, and Zr, contains no more than 1.0 mass % of Ag, no more than 0.08 mass % of Ti, no more than 2.0 mass % of Ni, no more than 3.5 mass % of Zn, and no more than 0.5 mass % of Cr, Fe, In, P, Si, Sn, and Zr by the total of the at least one element selected from the group, the remainder comprising Cu and impurities, has a conductivity of at least 60% IACS, has a tensile strength of at least 350 MPa, and has I(311)/IO(311) determined by X-ray diffraction in the thickness direction of the plate surface that satisfies the formula I(311)/IO(311)≧0.5.