PCB Contact Layer Structure for Heat-Spreader Delamination
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Solution Overview
Problem
The existing Printed-Circuit-Board (PCB) structures in RF generators face issues with thermal stress and delamination due to different coefficients of thermal expansion between the PCB and the heat spreader, leading to overheating, damage, and reduced efficiency in heat removal.
Innovation Solution
A PCB structure with an additional contact layer laminated onto the metallic layer, which fills gaps and provides a homogeneous surface for bonding, ensuring a strong and reliable connection to the heat spreader, reducing delamination and thermal cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the PCB is bonded directly to the heat spreader, then heat removal efficiency is improved, but thermal stress causes delamination and cracks
Solution Approach 1:
A contact layer is introduced as an intermediary between the PCB and heat spreader. This contact layer has a coefficient of thermal expansion that is intermediate between the PCB and heat spreader materials, acting as a buffer that reduces thermal stress during temperature cycling while maintaining effective thermal contact for heat removal
Solution Approach 2:
The bonding structure uses a composite material system consisting of the PCB, contact layer, and heat spreader bonded together. The contact layer is made of a material specifically selected to have intermediate CTE properties, creating a composite structure that combines the benefits of direct thermal contact with stress reduction
2Productivity
If industrial oven soldering is used, then manufacturing productivity is improved, but thermal stress during soldering causes delamination
Solution Approach 1:
The contact layer is applied beforehand to the PCB before the bonding process. This pre-applied layer serves as a protective cushion that will absorb thermal stress during subsequent industrial oven soldering operations, allowing high-productivity soldering processes to be used without causing delamination
3Reliability
If manual soldering is used, then thermal stress is reduced, but manufacturing time and cost increase
Solution Approach 1:
The contact layer serves as a protective intermediary that enables the use of high-speed automated soldering processes by absorbing thermal stress, thereby maintaining reliability while improving manufacturing productivity compared to manual soldering
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
Enhances heat transfer and bonding strength, allowing for standard industrial soldering processes while increasing the lifetime and reliability of the PCB structure.
Implementation Method 1
a contact layer (26) which is connected to a lower surface (28) of the basic PCB (22). The contact layer (26) is laminated onto the metallic layer (30)
Implementation Method 2
The lower surface (20) of the contact layer (26) is bonded to a heat spreader (14) by a bonding layer (16)
Implementation Method 3
The lower surface (20) of the contact layer (26) is bonded to a heat spreader (14)
Data Source
AI summary
Printed-Circuit-Board structure, in particular for an RF generator, including a heat spreader; a basic printed-circuit-board, PCB, having an upper surface and a lower surface, wherein the basic PCB includes a metallic layer at the lower surface having at least one conductor line and/or at least one contact pad; a contact layer. The contact layer is includes an upper surface directly connected to the metallic layer of the basic PCB and a lower surface; wherein the lower surface of the contact layer is bonded to the heat spreader by a bonding layer.