Printed Wiring Board Adhesive Layer Thermal Stress
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Solution Overview
Problem
Existing printed wiring boards face challenges with peeling and cracking between conductor layers and resin insulating layers, especially under thermal stress, due to differences in coefficient of thermal expansion and stress accumulation with increasing numbers of conductor layers.
Innovation Solution
A printed wiring board design featuring an insulating layer, a conductor layer with a smooth surface, an adhesive layer with a smooth film and protruding parts, and a resin insulating layer containing inorganic particles. The adhesive layer is sandwiched between the conductor and resin insulating layers, with a lower concentration of inorganic particles in the spaces between protrusions, reducing thermal deformation differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple conductor layers are stacked to increase functionality, then device complexity and productivity are improved, but stress accumulation and peeling between layers worsen due to thermal expansion differences
Solution Approach 1:
The patent changes the physical-chemical parameters of the adhesive layer by incorporating inorganic particles with specific coefficients of thermal expansion that match the conductor layers. This parameter adjustment allows the adhesive layer to withstand thermal stress in multilayer configurations, enabling higher productivity through increased layer count while maintaining reliability
Solution Approach 2:
The patent creates a composite adhesive layer combining organic adhesive material with inorganic particles. This composite structure provides both the adhesive bonding properties needed for layer attachment and the thermal expansion characteristics needed to match conductor layers, resolving the contradiction between multilayer functionality and interlayer adhesion reliability
2Ease of manufacture
If conventional adhesive layers are used between conductor and resin insulating layers, then ease of manufacture is maintained, but peeling and cracking occur under thermal stress
Solution Approach 1:
The patent modifies the adhesive layer composition by adding inorganic particles with specific thermal expansion coefficients, changing its physical parameters to resist thermal stress while maintaining manufacturability through conventional lamination processes
Solution Approach 2:
The adhesive layer acts as an intermediary between the conductor layer and resin insulating layer, with its modified composition serving as a buffer that absorbs thermal expansion differences and prevents stress transmission that would cause peeling or cracking
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 design enhances adhesion between conductor and resin insulating layers, reduces the likelihood of peeling and cracking, and maintains structural integrity under thermal stress, even with multiple conductor layers.
Implementation Method 1
differences in coefficient of thermal expansion and stress accumulation with increasing numbers of conductor layers
Data Source
AI summary
A printed wiring board includes an insulating layer, a conductor layer formed on the insulating layer, an adhesive layer formed on the conductor layer and including organic material, and a resin insulating layer formed on the insulating layer such that the resin insulating layer is covering the adhesive layer on the conductor layer formed on the insulating layer. The resin insulating layer includes resin and inorganic particles dispersed in the resin, and the adhesive layer has a smooth film part and a protruding part including protrusions protruding from the smooth film part such that a number of the inorganic particles in spaces between the protrusions with respect to a predetermined area is smaller than a number of the inorganic particles outside the spaces between the protrusions with respect to the predetermined area.