Built-In Component Board Pad Structure for Laser Heat Isolation
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Solution Overview
Problem
The increase in temperature during laser beam machining for forming cavities in insulating resin layers leads to a decrease in the sticking force between the copper pad layer and the insulating resin layer, affecting the quality of the interface.
Innovation Solution
Incorporating a metal pad layer with lower thermal conductivity than the wiring layer, such as nickel, to mitigate the heat propagation and maintain the sticking force, and using a high elastic modulus material to prevent delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser beam machining is used to form cavities in insulating resin layers, then high-density component mounting is achieved, but the temperature of the copper pad layer increases causing decreased sticking force
Solution Approach 1:
A metal layer with lower thermal conductivity than copper is introduced as an intermediary between the copper pad layer and the insulating resin layer. This intermediate layer acts as a thermal barrier that blocks heat propagation from the laser machining process to the interface between the copper pad layer and insulating resin layer, thereby preventing degradation of adhesion while allowing the laser machining process to proceed.
Solution Approach 2:
The pad structure is transformed from a single-material copper layer to a composite multi-layer structure consisting of copper pad layer, intermediate metal layer with lower thermal conductivity, and insulating resin layer. This composite structure combines the electrical conductivity benefits of copper with the thermal insulation properties of the intermediate layer, resolving the contradiction between machining efficiency and adhesion quality.
2Reliability
If copper pad layer is used for high electrical conductivity, then electrical performance is improved, but thermal conductivity increases causing heat propagation during laser machining
Solution Approach 1:
The pad layer is segmented into functionally distinct layers: a copper layer for electrical conductivity and an intermediate metal layer with lower thermal conductivity for thermal management. This segmentation allows each layer to independently fulfill its specific function without compromising the other, enabling the copper layer to maintain high electrical conductivity while the intermediate layer prevents excessive heat propagation.
Solution Approach 2:
The intermediate metal layer serves as a thermal mediator that decouples the thermal and electrical functions. It allows electrical current to pass through (maintaining circuit continuity) while blocking thermal energy propagation from the laser machining zone to the copper pad layer, thus resolving the contradiction between electrical performance and thermal management.
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 effectively suppresses the decrease in sticking force and prevents delamination between the metal pad layer and insulating resin layer, ensuring reliable adhesion and stability of electronic components.
Implementation Method 1
A metal used for the metal pad layer includes a metal having thermal conductivity that is lower than that of a metal used for the wiring layer
Implementation Method 2
In a step of forming a cavity in a part of the insulating resin layer by using a process of laser beam machining, the temperature of the copper pad layer that is located on the bottom surface of the cavity is increased caused by processing heat generated at the time of the process of laser beam machining
Data Source
AI summary
A built-in component board includes a first insulating layer; wiring layer and a metal pad layer that are formed on the first insulating layer; a second insulating layer that is formed on the wiring layer and the metal pad layer; and a cavity that is formed on the second insulating layer and that exposes the metal pad layer. Furthermore, the built-in component board includes an electronic component that is mounted on the metal pad layer; and a filling layer that is filled in the cavity and that buries the electronic component. Furthermore, a metal used for the metal pad layer includes a metal having thermal conductivity that is lower than that of a metal used for the wiring layer.