BGA Masking Dam Prevents Conformal Coating Bridging
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Solution Overview
Problem
Conformal coatings applied to circuit boards often bridge between components and the board, causing solder joints to break due to mismatched coefficients of thermal expansion, leading to damage and failure.
Innovation Solution
A masking dam with a removable cover and frame, featuring a seal to engage the circuit board and a securing mechanism, is used to prevent conformal coatings from bridging, custom-made through 3-D printing to fit unique components and withstand high temperatures, ensuring the solder joints are protected from thermal expansion mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conformal coating is applied to protect circuit board components, then protection against moisture and chemicals is improved, but the coating bridges between component and board causing solder joint failure
Solution Approach 1:
The masking dam divides the circuit board surface into protected zones (under components) and coated zones (exposed areas). The dam structure creates physical segments that prevent conformal coating from bridging between components and the board, eliminating the harmful thermal expansion stress on solder joints while maintaining protection where needed.
Solution Approach 2:
The masking dam acts as an intermediary barrier between the conformal coating and the solder joints. It prevents direct contact between the coating and the sensitive solder areas, allowing the coating to be applied for protection without causing the bridging problem that leads to solder joint failure.
2Reliability
If conformal coating is applied to prevent moisture damage, then moisture protection is improved, but thermal expansion mismatch causes solder joints to crack
Solution Approach 1:
The masking dam creates distinct segments on the circuit board - areas under the dam remain uncoated while areas outside are coated. This segmentation prevents the conformal coating from creating a continuous bridge between components and the board, eliminating the thermal expansion stress that causes solder joint cracking while maintaining moisture protection in coated areas.
Solution Approach 2:
The harmful conformal coating is extracted or removed from the sensitive areas where it would cause solder joint damage. The masking dam enables selective application, taking out the coating from regions near solder joints while maintaining it in areas where moisture protection is needed, thus resolving the contradiction between protection and joint integrity.
3Reliability
If a masking dam is used to prevent coating bridging, then solder joint protection is improved, but device complexity increases
Solution Approach 1:
The masking dam utilizes flexible or compliant seal elements that can conform to the circuit board surface and component contours. This approach provides effective sealing and protection against coating bridging while maintaining a relatively simple overall structure that is easy to apply and remove, minimizing the increase in device complexity.
Data Source
AI summary
The proposed masking dam protects ball grid array integrated circuit components from conformal coating overflow, preventing joint breakage and thermal mismatch. The masking dam includes a frame with an integrated seal, a cover, and a fastening mechanism. The frame is sealed to a circuit board surround a component, the cover is attached to the frame, and the masking dam is secured to protect the component.