Elastomeric Damming for PCB Noise Reduction
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Solution Overview
Problem
Electronic devices experience undesirable noise due to vibrations from components like ceramic capacitors, which are coupled to printed circuit boards through stiff underfill materials, leading to mechanical coupling and noise generation.
Innovation Solution
The use of a more viscous elastomeric material as an encapsulant to prevent underfill from reaching vibrating components, reducing mechanical coupling by forming a barrier and damping vibrations, thereby minimizing noise. This is achieved through a liquid polymer adhesive dispensing tool that applies the elastomeric material before underfill, ensuring it cures to a softer state than the underfill, reducing stiffness and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If underfill material is used to secure integrated circuits to printed circuit boards, then mechanical coupling and structural stability are improved, but vibrations from capacitors are transmitted to the board causing noise
Solution Approach 1:
The underfill application is segmented into two distinct zones: a first underfill material is applied only in a first region around the integrated circuit to provide structural stability, while a second underfill material (or no underfill) is used in a second region around capacitors to prevent vibration transmission. This spatial segmentation allows each component to have optimized support characteristics.
Solution Approach 2:
Different regions of the printed circuit board are assigned different underfill properties: the region around integrated circuits receives underfill with higher structural support characteristics, while the region around capacitors receives underfill with reduced vibration coupling characteristics. This local differentiation resolves the contradiction by providing stability where needed while minimizing noise where harmful vibrations occur.
2Reliability
If underfill is applied to secure components, then component attachment reliability is improved, but vibration coupling from capacitors to the board increases
Solution Approach 1:
The underfill material application is segmented into different types in different locations: integrated circuits receive underfill for reliable attachment, while capacitors are either left without underfill or receive a modified underfill formulation that reduces vibration coupling. This segmentation maintains reliability for critical components while reducing harmful vibration transmission from piezoelectric capacitors.
Solution Approach 2:
The underfill material properties are locally optimized: in regions where strong attachment is needed (around integrated circuits), underfill is applied with standard or enhanced adhesion characteristics; in regions where vibration coupling should be minimized (around capacitors), underfill is either omitted or formulated with damping properties. This local quality differentiation resolves the reliability versus vibration coupling contradiction.
3Object-generated harmful factors
If elastomeric material is used to prevent underfill from reaching capacitors, then vibration damping is improved, but manufacturing process complexity increases
Solution Approach 1:
The elastomeric material is applied in advance as a barrier layer before the underfill material is dispensed. This preliminary action prevents underfill from wicking under capacitors during subsequent processing steps, eliminating the need for complex real-time control mechanisms and simplifying the overall manufacturing process while achieving vibration damping.
Solution Approach 2:
The elastomeric material serves as an intermediary barrier between the underfill material and the capacitors. It allows the underfill to be applied for structural support while blocking it from reaching the capacitor regions, thereby decoupling the conflicting requirements of structural integrity and vibration isolation without complicating the manufacturing process.
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 effectively suppresses vibrations and noise by decoupling capacitors from the printed circuit board, resulting in a quieter operation of electronic devices by using a softer elastomeric material to dampen vibrations, reducing the transmission of mechanical forces and noise.
Implementation Method 1
underfill from wicking under the capacitors
Implementation Method 2
damping vibrations, thereby minimizing noise
Data Source
AI summary
An electronic device may be provided with integrated circuits and electrical components such as capacitors that are soldered to printed circuit boards. Liquid polymer adhesive such as encapsulant and underfill materials may be deposited on the printed circuit. Electrical components such as capacitors may be coated with the encapsulant. The underfill may be deposited adjacent to an integrated circuit, so that the underfill wicks into a gap between the integrated circuit and the printed circuit board. The encapsulant may be more viscous than the underfill and may therefore prevent the flowing underfill from reaching the electrical components. Some of the encapsulant may be located between the electrical components and the printed circuit board. The encapsulant can be cured to form an elastomeric material covering the electrical components that helps damp vibrations. The elastomeric material may be less stiff than the underfill.