Microcircuit Card Flatness via Low-Shrinkage Central Layer
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Solution Overview
Problem
Hot lamination techniques for manufacturing microcircuit cards result in uneven flatness due to differing shrinkage coefficients of materials, leading to stress and undulation of flex circuits, which is incompatible with quality standards.
Innovation Solution
A prelam structure is formed with a central layer of low shrinkage plastic, such as biaxially-oriented polyethylene terephthalate (PETf), sandwiched between layers of higher shrinkage plastic like polyvinyl chloride (PVC), with the flex circuit and resin embedded in a cavity, allowing hot lamination at temperatures up to 130°C without significant deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hot lamination is used to manufacture microcircuit cards, then manufacturing speed and productivity are improved, but the flatness of the card deteriorates due to differential shrinkage between materials
Solution Approach 1:
The patent applies local quality by creating a prelam structure with non-uniform shrinkage characteristics - the central layer has low shrinkage coefficient to match the flex circuit, while the outer layers have higher shrinkage. This localized differentiation of material properties allows the overall structure to maintain flatness during hot lamination while enabling high-speed manufacturing.
Solution Approach 2:
The patent uses composite materials by combining multiple plastic layers with different shrinkage coefficients (typically PVC layers with 3-5% shrinkage and a central low-shrinkage layer) to create a prelam that compensates for differential shrinkage. This composite structure resolves the contradiction between hot lamination speed and flatness maintenance.
2Ease of manufacture
If conventional prelam structure with uniform high shrinkage plastic is used, then ease of manufacture is improved, but the flatness during hot lamination deteriorates due to stress on flex circuit
Solution Approach 1:
The prelam structure incorporates a central layer with low shrinkage coefficient positioned at the cavity location, while outer layers maintain conventional high shrinkage properties. This local differentiation ensures that the flex circuit area experiences matched shrinkage, preventing stress and undulation, while the rest of the prelam maintains ease of manufacture through conventional materials.
Solution Approach 2:
The low-shrinkage central layer acts as an intermediary between the flex circuit and the high-shrinkage outer prelam layers. It mediates the shrinkage forces by providing a compliant interface that matches the flex circuit's thermal behavior, preventing direct stress transmission that would cause undulation.
3Manufacturing precision
If cold lamination is used to maintain flatness, then manufacturing precision is improved, but productivity deteriorates due to slow manufacturing cycle
Solution Approach 1:
The patent changes the shrinkage parameter of the prelam structure by incorporating a low-shrinkage central layer, enabling the use of hot lamination temperatures (typically 130°C or higher) without compromising flatness. This parameter modification allows transitioning from slow cold lamination to fast hot lamination while maintaining quality.
Solution Approach 2:
By creating a composite prelam with mixed shrinkage characteristics, the patent enables hot lamination to be used - a process that would normally cause flatness issues with uniform high-shrinkage materials. The composite structure reconciles the need for high-temperature processing with the requirement for dimensional stability.
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 approach ensures the microcircuit card maintains flatness by matching the shrinkage properties of the flex circuit with the surrounding layers, preventing curvature and undulation effects, thus meeting quality standards.
Implementation Method 1
the expansion, or shrinkage, coefficients of less than 1, very close to zero, whereas the constituent materials (in practice PVC, ABS, PLA, PC, PETg) of the prelam, surrounding the cavity occupied by the flex circuit, have expansion/shrinkage coefficients of several percent at 130° C.
Implementation Method 2
shrinkage phenomena of the plastics occur during the cooling (that is to say the opposite of the expansion phenomenon that takes place during the increase in temperature from ambient temperature up to the hot lamination temperature)
Data Source
AI summary
The method for producing a microcircuit card including a film having a very low level of shrinkage between two overlay layers, carrying at least one electronic component and an assembly of layers in which a cavity is formed containing the film and the electronic component, involves: forming the assembly to include a central layer 16 made from a material having a very low level of shrinkage between two layers of a plastic material having a substantially higher level of shrinkage, for example PVC, forming, through the assembly, a cavity of which the surface area advantageously equals between 30% and 90% of the surface area of the outer faces of the microcircuit card that is to be produced, embedding the film and the electronic component in a resin so as to occupy the space in the cavity and laminating the two overlay layers.