Circuit Board Polymer Jacketing for Thermal Dissipation
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Solution Overview
Problem
Existing circuit board manufacturing processes face challenges in protecting electronic components with complex and imprecise geometries from environmental stresses and structural support, as conventional conformal coatings and potting materials can cause damage due to thermal expansion mismatches and residual stresses, leading to failures such as solder joint failure and component detachment during temperature cycling.
Innovation Solution
A protective layering process using a combination of flexible and rigid molds to apply close-forming, encapsulating polymer layers that precisely conform to the circuit board assembly's geometry, providing structural support and thermal management while allowing for differential thermal expansion, and preventing potting material intrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conformal coatings are applied to protect circuit board assemblies, then protection from moisture and chemicals is improved, but the coating thickness control and pin-hole formation become difficult to manage
Solution Approach 1:
The patent applies a thin polymer film (such as parylene) that is deposited as a conformal coating. This flexible film provides superior moisture and chemical protection while achieving uniform thickness through vapor deposition processes, eliminating the pin-hole issues associated with liquid conformal coatings.
2Strength
If potting materials are used to encapsulate electronic components, then structural support and shock resistance are improved, but thermal expansion mismatches cause residual stresses and component damage
Solution Approach 1:
The patent modifies the thermal properties of the protective coating by selecting polymer materials with thermal expansion coefficients that match those of the electronic components and circuit board. This parameter matching eliminates thermal expansion mismatches and prevents residual stress buildup during temperature cycling.
Solution Approach 2:
The patent employs a composite protective system consisting of multiple layers: a thin polymer film (such as parylene) deposited directly on components, followed by a potting material. This composite structure provides both the protective benefits of the polymer film and the structural support of the potting material, while the film acts as a stress-isolation layer.
3Reliability
If a close-fitting polymer layer is applied over circuit board assembly, then protection from environmental factors is improved, but heat dissipation from electronic components is reduced
Solution Approach 1:
The patent uses an extremely thin polymer film (typically less than 25 micrometers, often only a few micrometers thick) that provides effective environmental protection while being sufficiently transparent to thermal energy. This thin film allows heat from electronic components to pass through via conduction and radiation without significant thermal resistance.
Solution Approach 2:
The patent utilizes the phase transition properties of heat transfer through the polymer film, where thermal energy passes through the film in various forms (conduction through the solid film, radiation through molecular vibrations). The thin film structure ensures that thermal energy can efficiently transition through the protective layer without causing overheating.
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 process ensures a tight, stress-reducing fit of polymer layers to electronic components, preventing damage from thermal expansion, providing EMI shielding, and enabling easier serviceability, while maintaining structural integrity during high-g force events and temperature fluctuations.
Implementation Method 1
A first thermally conductive layer is placed directly on top of the interface layer. The first thermally conductive layer comprises a high thermal conductivity filler dispersed in a polymer matrix.
Implementation Method 2
The populated circuit board is then heated and a vacuum is drawn through the mold, pulling the heated layer into a substantially precise representation of the circuit board assembly.
Implementation Method 3
The populated circuit board is then heated and a vacuum is drawn through the mold, pulling the heated layer into a substantially precise representation of the circuit board assembly.
Data Source
AI summary
A polymer layering process that encapsulates and protects electronics components with complex and imprecise geometries. The protective layering process provides a combination of a flexible mold and/or a rigid mold that apply close-forming, encapsulating the polymer layers to the electronic components and precision assemblies. Polymer layer protective jackets are shaped to as-populated circuit boards and assemblies, providing tightly fit barriers with fine resolution accommodating imprecise geometries. The protective jackets 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 external electromagnetic emissions. By altering the protect layer configuration, the protective layer can accommodate populated circuit board assembly with high heat generation component(s).