Polymer Film Encapsulation for PCB EMI Shielding and Thermal Stress Relief
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conformal coatings used in circuit board manufacturing face challenges such as difficulty in controlling thickness, pin-hole formation, and penetration by water molecules, while potting materials cause residual stresses and accessibility issues due to their permanent nature, leading to failures during temperature cycling and high-g force events.
Innovation Solution
A process involving a combination of flexible and rigid molds to apply close-forming, encapsulating polymer layers that precisely conform to the complex and imprecise geometries of electronic components, providing a barrier against potting material intrusion and thermal expansion stresses, without the need for adhesives or melting operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conformal coatings are applied to protect circuit board assemblies, then protection from moisture, dust, chemicals, and temperature extremes is improved, but control of coating thickness and prevention of pin-hole formation deteriorates
Solution Approach 1:
The patent applies a thin polymer film (such as polyimide) as a flexible encapsulating layer over the circuit board assembly. This film provides superior protection compared to conformal coatings while being formable to closely conform to the assembly's geometry, thereby achieving both reliable protection and manufacturing feasibility without pin-holes or thickness control issues.
Solution Approach 2:
The patent segments the protective structure into multiple functional layers: a thin polymer film layer for environmental protection and EMI shielding, and optionally a potting material layer for mechanical support. This segmentation allows each layer to perform its specific function optimally, with the polymer film providing the critical barrier function without the defects of conformal coatings.
2Strength
If potting materials are used to encapsulate electronic components, then structural support against shock and vibration is improved, but residual stresses and thermal expansion stresses increase
Solution Approach 1:
The patent introduces a thin polymer film layer beforehand, before applying the potting material. This intermediate layer acts as a stress-relief cushion that prevents the potting material from directly bonding to and stressing the electronic components during thermal cycling and mechanical shock, thereby reducing residual and thermal expansion stresses while maintaining structural support.
Solution Approach 2:
The thin polymer film serves as an intermediary layer between the electronic components and the potting material. This mediator prevents direct contact and stress transfer from the rigid potting material to the sensitive components, allowing the system to withstand shock and vibration while minimizing stress accumulation.
3Reliability
If a thin polymer layer is applied to provide environmental protection and EMI shielding, then protection from moisture and EMI is improved, but the complexity of the manufacturing process increases
Solution Approach 1:
The patent merges multiple protective functions (environmental protection, EMI shielding, and stress relief) into a single thin polymer film layer. This consolidation provides comprehensive protection without requiring multiple separate manufacturing steps, thereby reducing overall process complexity while maintaining superior reliability.
4Ease of manufacture
If conformal coatings are applied by wet-process, then application flexibility is improved, but the use of hazardous chemicals and drying/curing requirements worsen
Solution Approach 1:
The patent replaces the chemical-based conformal coating process with a mechanical/physical process: applying a pre-formed thin polymer film through lamination or wrapping. This substitution eliminates hazardous chemicals and drying/curing requirements while maintaining application flexibility and providing superior protective performance.
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 ensures a tight, precise fit of polymer layers to circuit board assemblies, reducing stresses, preventing component detachment, and providing environmental and EMI shielding, while allowing for differential thermal expansion and easy serviceability.
Implementation Method 1
A major disadvantage with encapsulants or potting materials however, is the fact that they are permanent solid bodies that prevent any access or servicing of the components they encapsulate. Potting materials are almost always thermoset materials that harden once and cannot not be re-softened or reused
Implementation Method 2
A thin polymer layer, or multiple thin layers, could be selected to provide various additional attributes, such as, improved heat dissipation, ESD and EMI protection and control
Implementation Method 3
After being cured, potting materials could cause high stresses, such as a residual stress and a thermal expansion stress, during temperature cycling, due to the coefficient of thermal expansion mismatches
Data Source
AI summary
A protective layering process that encapsulates and protects printed circuit board assemblies with complex and imprecise geometries. The protective layering process provides a combination of a flexible mold and/or a rigid mold, which are derived from modified data from a 3 dimensional scan of the printed circuit board assembly, and which applies close-forming, encapsulating polymer layers, electrically non-conductive layers, EMI shielding layers, and/or thermal management layers to the electronic components and circuit board assemblies. Polymer layers and protective jackets are shaped to as-populated circuit boards and assemblies, providing tightly fit barriers with fine resolution accommodating imprecise geometries. The protective jackets/layers can be formed in rigid, semi-rigid, or highly flexible polymer films, to protect the circuitry from the elements, CTE mismatches, shock and vibration loads and extreme g-forces, and from internal and external EMI and to manage thermal dissipation. Multiple, nesting layers, each with different protective properties, can be formed and applied.