Board Pad and Via Layout for Bump Current Distribution

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Solution Overview

Problem

Currents concentrate on some bumps when a first board with electronic components is mounted on a second board, leading to potential disconnection due to excessive current flow, which can damage the bumps.

Innovation Solution

The solution involves designing boards with insulating films and wiring layers that include power source and ground pads surrounding a capacitor region, where some pads are partially or fully disconnected from vias to distribute current flow, and using a computer-assisted design method to adjust pad connections based on current flow analysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple components (display device, sensor device, camera device) are integrated into a wearable device, then functionality and utility are improved, but device complexity and difficulty of achieving aesthetic design increase

Engineering Contradiction:
ImprovefunctionalityVSAvoiddesign complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies nesting by placing the sensor device and camera device within or behind the display device structure. The sensor device is positioned to extend through the display device, and the camera device is integrated into the same housing, creating a compact nested arrangement that reduces overall device complexity while maintaining multiple functions.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent utilizes the thickness dimension of the wearable device to arrange components vertically rather than horizontally. The first and second portions are positioned at different thickness positions, allowing multiple components to coexist in a compact form factor without increasing lateral dimensions, thus simplifying the overall design.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If design data is manually created for each view angle, then design precision is improved, but productivity and development time deteriorate

Engineering Contradiction:
Improvedesign precisionVSAvoiddevelopment efficiency
Core Design Contradiction:
Manufacturing precisionVSProductivity

Solution Approach 1:

The patent uses the three-dimensional model as a master copy from which two-dimensional design data for various view angles is automatically generated. This copying approach ensures consistent design precision across all views while eliminating the need to manually create each view separately, significantly improving productivity.

Inventive Principle:
Principle #26Copying

Solution Approach 2:

The patent replaces the manual mechanical process of creating design data for each view angle with an automated computer-based system. The design data generation apparatus automatically processes the three-dimensional model to generate consistent two-dimensional design data across multiple view angles, eliminating manual repetition and improving both precision and efficiency.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Shape

If aesthetic design is prioritized in wearable devices, then appearance quality is improved, but integration of multiple functional components becomes more difficult

Engineering Contradiction:
Improveappearance qualityVSAvoidcomponent integration
Core Design Contradiction:
ShapeVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by making different portions of the display device have different properties. The first portion maintains high aesthetic quality for visibility, while the second portion is optimized for sensor functionality. This localized differentiation allows the device to achieve both aesthetic design and functional integration without compromise.

Inventive Principle:
Principle #3Local quality

Data Source

PatentEP3855482B1Electronic device, electronic apparatus, and design assistance method for electronic device
Publication Date: 2026.05.06 FUJITSU LTD
  • EP3855482B1 patent drawingFigure 1A~1B
  • EP3855482B1 patent drawingFigure 2
  • EP3855482B1 patent drawingFigure 3

AI summary

There is provided an electronic device including a board that includes an insulating film, a wiring layer and a via provided in the insulating film, and a plurality of power source pads and a plurality of ground pads which are provided in the insulating film so as to surround a capacitor region in which a capacitor is provided and to which a plurality of bumps is coupled, and an electronic component that is mounted at the board, and is electrically coupled to the plurality of power source pads and the plurality of ground pads through the wiring layer and the via. At least one of a case where the plurality of power source pads includes one or a plurality of first power source pads with which the via is in contact and one or a plurality of second power source pads of which a total area in contact with the via is smaller than a total area of the one or plurality of first power source pads in contact with the via in a column lined up along a side of an outline of the capacitor region so as to be adjacent to the capacitor region and a case where the plurality of ground pads includes one or a plurality of first ground pads with which the via is in contact and one or a plurality of second ground pads of which a total area in contact with the via is smaller than a total area of the one or plurality of first ground pads in contact with the via in the column lined up along the side of the outline of the capacitor region so as to be adjacent to the capacitor region is satisfied.