Copper Paste Position Sensor Warping Prevention
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Solution Overview
Problem
Conventional position detection sensors using silver paste face high costs and ion migration issues, while copper paste leads to oxide film formation and shrinkage problems, causing warping and undulation in compact portable terminals.
Innovation Solution
A position detection sensor using copper paste with wiring patterns formed on both surfaces of a polyimide-based resin board, with patterns extending orthogonally to each other to evenly distribute shrinkage and prevent warping, ensuring accurate position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver paste is used for position detection sensors, then conductivity is improved, but cost increases and ion migration occurs
Solution Approach 1:
The patent replaces expensive silver paste with cheaper copper paste, accepting that copper has shorter service life due to oxidation. The copper paste provides adequate conductivity for the application while significantly reducing cost and eliminating ion migration issues that plague silver paste
2Ease of manufacture
If copper paste is used to reduce cost, then manufacturing cost is reduced, but oxide film formation occurs and conductivity degrades
Solution Approach 1:
The patent changes the thermal treatment parameters from conventional low-temperature (200-250°C) processes to high-temperature (above 300°C) reduction treatment. This parameter change converts copper oxide back to metallic copper, restoring conductivity while maintaining the cost advantage of using copper paste
3Reliability
If high temperature thermal treatment is applied to copper paste, then oxide film is reduced and conductivity is improved, but binder shrinks causing warping and undulation
Solution Approach 1:
The patent introduces a compensation mechanism where additional copper paste is applied to areas that will experience greater shrinkage during high-temperature treatment. This compensatory copper paste acts as a counterweight to the binder shrinkage, preventing warping and undulation while allowing the high-temperature reduction treatment to proceed for optimal conductivity
4Volume of moving object
If loop coil width and spacing are reduced for compact terminals, then device size is reduced, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The patent changes the thermal treatment temperature parameter to above 300°C, which causes the copper paste binder to shrink uniformly. This controlled shrinkage actually helps maintain precise loop coil dimensions and spacing during the sintering process, enabling compact terminal design while achieving the required manufacturing precision
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 maintains accuracy and prevents warping or undulation in position detection sensors, even with copper paste, by evenly distributing shrinkage across the board, thus enhancing the reliability of compact portable terminals.
Implementation Method 1
A position detection device having a position detection sensor permits detection of coordinates of a position pointed to by a position pointer in the X-axis and Y-axis directions based on electromagnetic induction action between the position pointer and the position detection sensor
Implementation Method 2
a binder included in the copper paste shrinks, leading to shrinkage of paste wiring itself made of copper paste. This shrinkage exerts a shrinking force on the sheet-shaped board
Data Source
AI summary
A position detection sensor includes a plurality of position detection loop coils formed on a board made of resin through a thermal process by forming a wiring path pattern made of copper paste that includes copper powder and a binder. Each of the position detection loop coils includes a plurality of first portions that extend on a first surface of the board in a first direction and a plurality of second portions that extend on a second surface of the board in a second direction that is orthogonal to the first direction. The wiring path pattern is disposed on the first surface and the second surface in a connector section that connects the position detection loop coils to external circuitry. The position detection sensor is capable of maintaining accuracy even though the loop coils are formed on the board by the thermal treatment using copper paste.