Crystalline Thermoplastic Polyimide Adhesive for Flexible Metal-Clad Laminates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional flexible printed circuit boards (FPCs) face challenges with post-moisture absorption solderability due to high water absorption coefficients of polyimide materials, leading to issues like swelling and adhesion failures during soldering, especially with the transition to lead-free soldering which requires higher temperature resistance.
Innovation Solution
A film with a crystalline thermoplastic polyimide adhesive layer is developed, characterized by a specific endothermic and exothermic peak area measured by differential scanning calorimetry, which improves the post-moisture absorption solderability and peeling strength of the flexible metal-clad laminate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polyimide material is used for the adhesive layer, then heat resistance and size stability are improved, but water absorption coefficient increases leading to poor post-moisture absorption solderability
Solution Approach 1:
The invention changes the glass transition temperature parameter of the polyimide adhesive layer to 200°C or higher, which fundamentally alters the material's thermal behavior and moisture resistance characteristics, thereby improving post-moisture absorption solderability while maintaining heat resistance
Solution Approach 2:
The invention utilizes the phase transition behavior of polyimide at elevated temperatures, specifically designing the adhesive layer to undergo glass transition at 200°C or higher, which prevents moisture-related defects during soldering processes by maintaining structural integrity through the phase transition
2Ease of manufacture
If thermally-curing adhesive agents (epoxy resin, acrylic resin) are used, then low temperature processability is improved, but heat resistance is insufficient
Solution Approach 1:
The invention changes the fundamental material type from thermally-curing resins to thermoplastic polyimide with elevated glass transition temperature, enabling both low-temperature bonding processability and high-temperature heat resistance simultaneously
3Reliability
If preliminary-drying process is added to remove moisture, then post-moisture absorption solderability is improved, but productivity decreases due to increased number of processes
Solution Approach 1:
The invention performs preliminary action by designing the adhesive layer with inherently low moisture absorption characteristics through elevated glass transition temperature, preventing moisture uptake before the soldering process begins, thereby eliminating the need for separate preliminary-drying steps
Solution Approach 2:
The adhesive layer material itself provides the moisture resistance function through its elevated glass transition temperature, making the material self-sufficient in preventing moisture-related defects without requiring external preliminary-drying processes
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 film and laminate exhibit excellent post-moisture absorption solderability and workability, maintaining integrity under high-temperature soldering conditions without swelling or whitening, while achieving sufficient peeling strength and adhesion.
Implementation Method 1
an absolute value of an endothermic peak area attributed to melting of the crystalline thermoplastic polyimide is 4.0 mJ/mg or higher, the endothermic peak area being measured by performing a differential scanning calorimetry on the film
Implementation Method 2
an absolute value of an endothermic peak area attributed to melting of the crystalline thermoplastic polyimide is 4.0 mJ/mg or higher
Data Source
AI summary
A film and a flexible metal-clad laminate obtained with the film. The laminate is improved in post-moisture absorption solderability. The film comprises a heat-resistant polyimide film and, disposed on at least one side thereof, an adhesive layer containing a thermoplastic polyimide. It is characterized in that the thermoplastic polyimide contained in the adhesive layer has crystallinity and that the film, when analyzed with a differential scanning calorimeter, has an endothermic peak attributable to the melting of the crystalline thermoplastic polyimide, the absolute value of the area of the peak being 4.0 mJ/mg or larger. The flexible metal-clad laminate is characterized by comprising the film and a metal layer disposed thereon.