PCB Core Board Structure for Power Device Solder Joint Reliability
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Solution Overview
Problem
Conventional PCB materials face challenges in meeting long-term reliability requirements due to increased thermal expansion and Young's modulus, leading to solder joint cracks in high-power devices.
Innovation Solution
Incorporating a flexible dielectric layer with a Young's modulus of less than or equal to 15 GPa between outer conductive layers, hybridly laminated with prepreg layers, to reduce the modulus and enhance solder joint reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of layers and copper thickness are increased to achieve high power and high density, then the power handling capability is improved, but the coefficient of thermal expansion and Young's modulus increase, causing solder joint reliability to deteriorate
Solution Approach 1:
The patent applies local quality by introducing a flexible dielectric layer specifically at the location where the solder joint is formed (between the first and second conductive layers). This localized modification reduces the Young's modulus only in the critical region affecting solder joint reliability, while the rest of the PCB structure maintains its rigid characteristics for power handling.
Solution Approach 2:
The patent uses composite materials by combining a flexible dielectric layer (with low Young's modulus) with conventional rigid dielectric layers in a multi-layer structure. This composite approach allows the PCB to have different mechanical properties in different regions, achieving both power handling capability and solder joint reliability.
2Strength
If conventional rigid dielectric layers are used throughout the PCB, then the structural strength is improved, but the solder joint reliability deteriorates due to high Young's modulus and thermal expansion
Solution Approach 1:
The patent introduces a flexible dielectric layer with low Young's modulus specifically at the solder joint location, while maintaining conventional rigid dielectric layers in other areas. This localized differentiation allows the PCB to have high structural strength overall while having low modulus at the critical solder joint region.
Solution Approach 2:
The patent segments the dielectric layers into different types: a flexible dielectric layer (first dielectric layer) at the solder joint location and conventional rigid dielectric layers (second dielectric layer) elsewhere. This segmentation allows each region to have optimized mechanical properties for its specific function.
3Reliability
If a flexible dielectric layer is introduced to reduce Young's modulus and improve solder joint reliability, then the solder joint reliability is improved, but the voltage withstand capability may deteriorate
Solution Approach 1:
The patent segments the dielectric structure into a flexible dielectric layer (first dielectric layer) with low Young's modulus for solder joint reliability, and a conventional rigid dielectric layer (second dielectric layer) with high voltage withstand capability. By placing these different material types in different locations, the patent achieves both solder joint reliability and voltage withstand capability.
Solution Approach 2:
The flexible dielectric layer is introduced only at the specific location where solder joint reliability is critical, while the conventional rigid dielectric layers maintain voltage withstand capability in other regions. This localized approach ensures that voltage withstand is not compromised by the flexible layer.
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 improves solder joint reliability and extends the service life of high-power devices by reducing the Young's modulus and coefficient of thermal expansion, while maintaining voltage withstand capability.
Implementation Method 1
hybridly laminated with prepreg layers
Implementation Method 2
a flexible dielectric layer whose Young's modulus is less than or equal to a preset Young's modulus
Implementation Method 3
reducing the Young's modulus and coefficient of thermal expansion
Data Source
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AI summary
Embodiments of this application provide a printed circuit board, including a core board and a substrate. The core board covers and is disposed on an outer surface of the substrate. The core board includes a first conductive layer, a second conductive layer, and a first dielectric layer. The first conductive layer is located on a side that is of the core board and that is away from the substrate, the second conductive layer is located on a side that is of the core board and that is close to the substrate, and the first dielectric layer is located between the first conductive layer and the second conductive layer, and includes a flexible dielectric layer whose Young's modulus is less than or equal to a preset Young's modulus. In the printed circuit board provided in embodiments of this application, a modulus of a PCB at the bottom of a solder joint of a power device is reduced, so that reliability of the solder joint between the power device and the PCB is improved and a service life requirement of a product is met. In addition, a voltage withstanding capability between an outermost conductive layer and a secondary outer conductive layer is enhanced.