Thermal Capacitors for PCB Temperature Balancing
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Solution Overview
Problem
In surface-mount technology, heat sinking surface-mount devices with higher thermal mass can lower the temperature of the assembly, leading to suboptimal soldering quality due to temperature gradients exceeding allowable limits when the entire reflow oven temperature is increased to compensate, potentially damaging components.
Innovation Solution
Incorporating thermal capacitors with varying thermal masses on the PCB, strategically positioned between heat sinking devices and the board's edges, to balance temperature across the assembly, using existing structural components like plated holes and pads for thermal coupling, and adjusting the heating profile to maintain desired temperatures and gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the temperature in the entire reflow oven device is increased to compensate for heat sinking devices, then the temperature in the vicinity of heat sinking surface-mount devices is maintained above the desired temperature value, but the temperature in regions distant from heat sinking devices exceeds the maximal allowable temperature value and temperature gradients across the assembly exceed maximal allowable temperature gradient values
Solution Approach 1:
The patent applies local quality by placing thermal capacitors specifically in regions with low thermal mass (away from heat sinking devices) to provide localized thermal balancing. This allows the reflow oven to maintain appropriate temperatures at heat sinking devices without causing excessive temperatures in other regions, as the thermal capacitors locally absorb or release heat where needed.
Solution Approach 2:
Thermal capacitors serve as intermediary elements between the heat sinking devices and the PCB regions that are temperature-sensitive. These capacitors mediate the thermal energy distribution, absorbing excess heat from high-temperature zones and releasing it to low-temperature zones, thereby preventing both overheating and underheating in different assembly regions.
2Temperature
If heat sinking surface-mount devices with higher thermal mass are present on the PCB, then they absorb more heat during heating, but the temperature of the assembly in their vicinity drops below or too close to the molting temperature of the solder paste
Solution Approach 1:
The patent applies preliminary action by pre-placing thermal capacitors on the PCB before the reflow soldering process. These capacitors are positioned in regions that will experience temperature drops due to heat sinking devices, so they are ready to release stored thermal energy when needed during heating, preventing the solder paste temperature from dropping below the molting temperature.
Solution Approach 2:
The patent changes the thermal parameters of the assembly by introducing components with specific thermal mass values (thermal capacitors) that are equal to or greater than the first thermal mass value of surface-mount devices. This modifies the overall thermal characteristics of the PCB assembly, creating a more balanced thermal profile that prevents excessive temperature drops in vulnerable regions.
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 effectively reduces temperature differences across the assembly to minimal levels, ensuring proper soldering and preventing thermal damage, thereby enhancing the quality of the surface-mount process for temperature-sensitive devices.
Implementation Method 1
one or a plurality of thermal capacitors (e.g. heat absorbing components) disposed on the PCB
Implementation Method 2
The PCB may include a plurality of structural components to dispose the thermal capacitors on the PCB and/or to thermally couple the thermal capacitors to the PCB
Data Source
AI summary
A device may include a printed circuit board (PCB), a plurality of surface-mount devices disposed on the PCB, wherein a thermal mass of each of the surface-mount devices ranges between a first thermal mass value and a second thermal mass value that is greater than the first thermal mass value, and a plurality of thermal capacitors disposed on the PCB, wherein a thermal mass of each of the thermal capacitors is equal to or greater than the first thermal mass value of the surface-mount devices.