Angled PCB Stack Encapsulation to Prevent Air Trapping

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Solution Overview

Problem

Existing methods for encapsulating circuit boards fail to effectively protect them from high G-loads and compression due to air entrapment within the encapsulating medium, which can cause damage to the physical components.

Innovation Solution

A method involving the use of a shell with an input and output orifice, where the shell is angled to minimize air entrapment by allowing the encapsulating compound to flow from the lowest to the highest point, utilizing relief paths on the boards and potentially degassing the compound for efficient filling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If encapsulating compound is injected horizontally or from the top, then the encapsulation process is simple, but air becomes trapped within the compound causing damage to circuit boards under high G-loads and compression

Engineering Contradiction:

Improveprotection from high G-loads and compressionVSAvoidencapsulation process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by positioning the input orifice at the lowest point of the shell's internal volume and angling the shell relative to horizontal. This asymmetric orientation ensures that the encapsulating compound flows from the lowest point upward, preventing air entrapment and eliminating the need for complex vacuum or vibration systems during encapsulation.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent inverts the conventional encapsulation approach by injecting the compound from the lowest point rather than from the top or side. This inversion, combined with angling the shell, allows air to escape naturally through the output orifice positioned at the highest point, achieving complete air removal without additional complexity.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If the shell is angled relative to horizontal with input orifice at the lowest point, then air entrapment is minimized and boards are protected from damage, but the encapsulation process becomes more complex

Engineering Contradiction:

Improveair-free encapsulationVSAvoidencapsulation process ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs self-service by designing the shell and orifice positioning system to automatically guide air escape during encapsulation. The angular orientation and strategic placement of input and output orifices create a self-draining effect where air naturally rises and exits through the highest point, eliminating the need for external vacuum systems or vibration mechanisms.

Inventive Principle:

Principle #25Self-service

3Strength

If circuit boards are spaced apart in a stack, then components are accessible and heat dissipation is improved, but the encapsulation volume increases and requires more compound

Engineering Contradiction:

Improvecomponent accessibility and heat dissipationVSAvoidencapsulating compound quantity

Core Design Contradiction:

StrengthVSQuantity of substance

Solution Approach 1:

The patent applies parameter changes by modifying the spatial arrangement parameters of the circuit boards within the shell. By optimizing the spacing and angular orientation of the stacked boards, the design achieves adequate component accessibility and heat dissipation while minimizing the total encapsulation volume required, thus reducing the quantity of encapsulating compound needed.

Inventive Principle:

Principle #35Parameter changes

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

This approach significantly enhances the ability of the encapsulated circuit board stack to withstand high G-loads and compression without damaging the components, by ensuring a thorough and air-free encapsulation.

Implementation Method 1

injecting an encapsulating compound into the input orifice to fill the internal volume of the shell with the encapsulating compound

Methodology Applied

Scientific EffectFluid flow under gravity: Gravitation

Implementation Method 2

heating and degassing an encapsulating compound

Methodology Applied

Scientific EffectThermal heating: Heating

Data Source

PatentUS7712213B2Angular encapsulation of tandem stacked printed circuit boards

Publication Date: 2010.05.11 AIRPORTS AUTHORITY OF INDIA

AI summary

A method is provided for making an encapsulated stack of circuit boards. The method includes assembling the stack of circuit boards from a plurality of circuit boards, the circuit boards being spaced apart from each other; inserting the stack into an internal volume of a shell, the shell having a first end and a second end opposite the first end, an input orifice adjacent the first end, and an output orifice adjacent the second end and on a side opposite the input orifice; positioning the shell such that the input orifice is at a lowest point of any part of the internal volume of the shell, and such that the output orifice is at a highest point of any part of the internal volume of the shell; angling the shell relative to horizontal; and injecting an encapsulating compound into the input orifice to fill the internal volume of the shell with the encapsulating compound.