Flexible PCB Enclosure Heat Spreader for Solder-Joint Reliability
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Solution Overview
Problem
Electronic devices face premature failure due to thermal cycling-induced solder-joint cracking on printed circuit boards, exacerbated by coefficient-of-thermal-expansion mismatches between components and the protective enclosure.
Innovation Solution
A protective enclosure with a flexible stamped-metal heat spreader and cured-liquid thermal interface materials (TIM) parts is used to reduce temperature gradients and mechanical loading on solder joints, employing a configuration that includes the heat spreader attached to the lid with a non-zero distance and TIM parts in contact with both the heat spreader and electronic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective enclosure is used to protect electronic devices, then device protection is improved, but thermal cycling-induced solder-joint cracking increases due to coefficient-of-thermal-expansion mismatch
Solution Approach 1:
A flexible heat spreader is introduced as an intermediary component between the rigid protective enclosure lid and the electronic components on the PCB. This heat spreader acts as a mediator that decouples the thermal expansion forces from the solder joints while still providing effective heat removal. The flexible material allows relative movement between the lid and PCB, preventing stress transmission to the solder joints during thermal cycling.
Solution Approach 2:
The patent changes the physical parameters of the interface between the enclosure and electronic components by introducing a flexible heat spreader with specific mechanical and thermal properties. This flexible component has different stiffness and thermal conductivity parameters compared to traditional rigid heat sinks, allowing it to accommodate thermal expansion while maintaining thermal management effectiveness.
2Temperature
If traditional rigid heat sinks are used, then heat removal is effective, but mechanical stress on solder joints increases during thermal cycling
Solution Approach 1:
The patent replaces traditional rigid heat sinks with a flexible heat spreader made of thin, compliant material. This flexible heat spreader can deform and flex during thermal cycling, absorbing mechanical stress that would otherwise be transmitted to the solder joints. The flexibility allows the heat spreader to conform to PCB dimensional changes while maintaining thermal contact with the electronic components.
Solution Approach 2:
The heat spreader transitions from a static, rigid structure to a dynamic, flexible component that can adapt its shape and position during thermal cycling. The flexible heat spreader dynamically responds to thermal expansion and contraction of the PCB, maintaining optimal thermal contact while preventing stress concentration at the solder joints through its ability to deform.
3Stability of the object's composition
If the heat spreader is attached directly to the lid, then structural stability is improved, but temperature gradients across the PCB increase
Solution Approach 1:
The flexible heat spreader serves as a thermal intermediary that distributes heat more evenly across the PCB surface. By contacting multiple electronic components and the lid simultaneously, it creates additional thermal conduction pathways that reduce temperature gradients. The flexibility ensures uniform thermal contact pressure across the PCB surface, preventing localized hot spots while maintaining structural stability.
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 configuration significantly reduces fatigue-inducing forces on solder joints, leading to a decrease in premature device failures by approximately 20% compared to traditional designs, by minimizing temperature gradients and mechanical stress.
Implementation Method 1
one or more first TIM parts, each of the one or more first TIM parts being in contact with and vertically between the heat spreader and a corresponding one of the electronic components
Implementation Method 2
a flexible, stamped-metal heat spreader connected, by way of cured-liquid TIM parts, to at least some of the packaged integrated circuits on one side of the PCB assembly
Data Source
AI summary
A protective enclosure for a PCB assembly, e.g., a solid-state-drive assembly. In an example embodiment, the enclosure comprises a flexible, stamped-metal heat spreader connected, by way of cured-liquid TIM parts, to at least some of the packaged integrated circuits on one side of the PCB assembly. In some embodiments, additional cured-liquid TIM parts may be connected between the body of the protective enclosure and packaged integrated circuits on the other side of the PCB assembly and/or the assembly's PCB. The PCB assembly, heat spreader, and various TIM parts are arranged in a manner that helps to significantly lower the risk of solder-joint failure under thermal cycling.