Compliant Insert Mitigates PCB Stress Under External Loads
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Solution Overview
Problem
Electronic assemblies face stress and potential failure due to external loads such as shock, vibration, and temperature cycling, which cause PCBs to flex and weaken solder connections, and existing encapsulation methods do not allow for easy disassembly or rework.
Innovation Solution
A compliant insert made of polymer material with a 3-D negative relief matching the geometric design of the electronics assembly, providing tailored support and pre-loading to absorb manufacturing tolerances and mitigate deflections, while allowing for disassembly and rework of the package.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid standoffs and bolts are used to assemble electronic assemblies to a lid, then the assemblies are securely fixed, but the solder connections are stressed and weakened under external loads
Solution Approach 1:
A compliant insert made of elastomeric material is introduced as an intermediary between the rigid lid and the electronic assembly. This insert has a 3-D negative relief that mirrors the 3-D positive relief of the assembly, creating a compliant interface that secures the assembly while absorbing stress, thereby protecting solder connections from mechanical loading
Solution Approach 2:
The patent changes the mechanical parameter of the interface material from rigid to elastomeric (compliant). The insert material has a durometer between 30 and 70 on the Shore A scale, allowing it to deform elastically under load, absorb shocks, and cycle with temperature changes without transmitting excessive stress to the solder connections
2Reliability
If encapsulant material is injected into the housing and cured to bond to PCBs and components, then the assemblies are protected from external loads, but the package cannot be disassembled for rework
Solution Approach 1:
The patent uses a flexible elastomeric insert instead of rigid encapsulant material. The insert is compressed between the lid and base, creating a secure, compliant bond that protects the assembly while allowing the package to be disassembled by releasing the compression, enabling rework if needed
Solution Approach 2:
The insert is designed to be dynamically compressible rather than permanently bonded. During assembly, the insert is compressed to secure the electronic assembly; during disassembly, the compression is released allowing the assembly to be removed and reworked, providing both protection and repairability
3Strength
If the compliant insert is made stiffer to better mitigate deflections under loading, then the support improves, but the insert cannot absorb manufacturing tolerances
Solution Approach 1:
The patent selects an optimal durometer range (30-70 on Shore A scale) that balances stiffness and compliance. This intermediate hardness allows the insert to be stiff enough to support the assembly and mitigate deflections under normal loading, while remaining compliant enough to absorb manufacturing tolerances and accommodate assembly variations
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 compliant insert effectively absorbs vertical and lateral tolerances, reduces stress on solder connections, and enables easy disassembly and rework of electronic assemblies, enhancing their durability and maintainability under external loads.
Implementation Method 1
The polymer material is compliant enough to absorb the vertical and lateral spacing tolerances of the electronic components
Implementation Method 2
The polymer material is compliant enough to absorb the vertical and lateral spacing tolerances of the electronic components and stiff enough to mitigate deflections under loading
Data Source
AI summary
A compliant insert is provided to support electronic assemblies to mitigate the effects of external loading. The insert comprises a polymer material having a durometer of between 10 and 90 on the Shore A scale and a 3-D negative relief on the surface of the polymer material. The 3-D negative relief is the negative of the 3-D positive relief of a specified geometric design of an electronics assembly. The compliant insert is mated with an instance of the electronics assembly such that the 3-D negative relief of the polymer material engages the 3-D positive relief of the assembly's PCB and electronic components. The polymer material is compliant enough to absorb the vertical and lateral spacing tolerances of the electronic components and stiff enough to mitigate deflections under loading.