1. Material Composition
Base Material: Typically, flexible circuits are made from polyimide or polyester films. Polyimide is preferred for its higher thermal stability.Copper Layer: The copper conductive layer can affect dimensional stability as it responds to temperature changes.
2. Thermal Expansion
Coefficient of Thermal Expansion (CTE): Each material in the flexible circuit has a CTE, which is crucial in determining how much the circuit will expand or contract with temperature changes.Balanced Construction: To improve stability, materials with complementary CTE values are used.
3. Moisture Absorption
Hygroscopic Nature: Flexible circuits can absorb moisture from the environment, which may cause swelling and affect dimensions.Encapsulation: Using protective coatings can help minimize moisture absorption and maintain dimensional stability.
4. Manufacturing Process Influences
Lamination Processes: The heat and pressure applied during the lamination can influence dimensional stability. Precise control of these parameters is essential.Etching: The chemical process used to define the circuit pattern can also affect dimensions slightly due to material removal.
5. Mechanical Stress
Flexing: Repeated flexing can lead to material fatigue and dimensional changes over time, especially at high flex cycles.Mounting Techniques: The methods used to mount or integrate the circuit into final products can impose mechanical stresses that alter dimensions.
6. Environmental Conditions
Temperature Variations: Extreme temperatures can lead to dimensional changes, both during operation and in storage.UV Exposure: Long-term exposure to UV light can degrade materials, affecting their structural integrity and size.
7. Long-Term Stability and Aging
Material Degradation: Over time, materials can degrade naturally, affecting the mechanical properties and stability of dimensions.Aging Effects*: Electrical, thermal, and environmental stresses over the lifespan can lead to changes in material properties.