Printed Wiring Board Conductor Post Segmentation for Crack Prevention
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Solution Overview
Problem
Existing printed wiring boards with embedded semiconductor elements face challenges in maintaining reliable connections and preventing cracks due to differences in strength between the semiconductor element and conductor posts, leading to potential stress concentration and reduced reliability during heat cycles.
Innovation Solution
The design includes a lowermost resin insulating layer with embedded semiconductor elements, conductor posts, and via conductors that connect the conductor layers and electrodes, with specific dimensions and configurations to balance strength and reduce stress, ensuring reliable connections and preventing cracks by adjusting the height and length of conductor posts and via conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the height of conductor posts is increased to improve connection reliability, then the strength difference between semiconductor elements and conductor posts increases, but stress concentration occurs leading to cracks
Solution Approach 1:
The conductor post is divided into multiple segments with different heights. Specifically, conductor posts are configured in a first region surrounding a semiconductor element and in a second region not surrounding the element, with the first region posts having a first height and the second region posts having a second height that is different from the first height. This segmentation allows optimization of connection reliability for embedded elements while preventing stress concentration in non-embedded regions.
Solution Approach 2:
Different conductor post heights are applied to different spatial regions based on local requirements. The first region (surrounding semiconductor elements) uses a first height optimized for reliable electrical connection, while the second region (not surrounding elements) uses a second height that prevents excessive stress concentration. This local differentiation resolves the contradiction between connection reliability and stress management.
2Reliability
If via conductors are made longer to connect deeper electrodes, then connection reliability improves, but manufacturing complexity and stress concentration increase
Solution Approach 1:
The via conductor system is segmented into two types: first via conductors connecting to electrodes in the first (upper) region, and second via conductors connecting to electrodes in the second (lower) region. This segmentation allows each via conductor type to be optimized for its specific connection depth, improving reliability while simplifying manufacturing compared to a single uniform via conductor system.
Solution Approach 2:
The conductor posts and via conductors are configured in advance with predetermined heights and positions before final assembly. The first via conductors are positioned to connect to upper electrodes, while second via conductors connect to lower electrodes. This preliminary configuration ensures reliable connections are established before stress cycles occur, while maintaining manageable manufacturing complexity through pre-planned geometry.
Data Source
AI summary
A printed wiring board includes a lowermost resin insulating layer, a first conductor layer formed on a first surface of the lowermost resin insulating layer, a conductor post formed in the lowermost resin insulating layer such that the conductor post has an upper surface facing the first surface and a lower surface on the opposite side with respect to the upper surface, a semiconductor element embedded in the lowermost resin insulating layer such that the semiconductor element has an electrode facing the first surface and is positioned on a second surface side of the lowermost resin insulating layer, and via conductors formed in the lowermost resin insulating layer and including a first via conductor and a second via conductor such that the first via conductor is connecting the first conductor layer and the conductor post and that the second via conductor is connecting the first conductor layer and the electrode.