Flexible PCB Pad Connection Layout for Compact Main Boards

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Solution Overview

Problem

The large structural sizes of electrical connectors in electronic devices occupy excessive space on the main board, hindering lightweight and thinning capabilities and reducing the capacity of function modules.

Innovation Solution

Integrate a pad group on the control main board with a flexible printed circuit board, using laser welding to connect pins of the second connecting terminal with the pads, optimizing space utilization and reducing the size of the control main board by integrating components like CPU, PMU, LDO, resistance, and capacitor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional electrical connectors are used to connect function modules to the main board, then reliable electrical connection is achieved, but the connectors occupy excessive space on the main board

Engineering Contradiction:
Improveelectrical connection reliabilityVSAvoidspace occupied by connectors on main board
Core Design Contradiction:
ReliabilityVSArea of stationary object

Solution Approach 1:

The patent merges the connector function directly into the main board by integrating pads that can be directly welded to flexible circuit boards. This eliminates the need for separate connector components, reducing the space they would normally occupy while maintaining reliable electrical connection through direct pad-to-flexible circuit board welding.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent extracts the connector functionality from separate components and integrates it into the main board structure. By removing the traditional connector assembly and replacing it with directly integrated pads, the design eliminates unnecessary intermediate components and reduces overall space requirements.

Inventive Principle:
Principle #2Taking out (Extraction)

2Adaptability or versatility

If multiple electrical connectors are provided on the main board for various function modules, then all functions can be connected, but the main board structure becomes extended and complex

Engineering Contradiction:
Improvefunction module connectivityVSAvoidmain board structure complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements a universal pad design that can serve multiple function modules. The pads are strategically positioned and designed to accommodate connections for power modules, camera modules, sensor modules, and other functions, allowing a single integrated solution to handle multiple connectivity requirements without increasing structural complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

By merging multiple connector functions into a single integrated pad system on the main board, the patent reduces the number of separate structural elements needed. This consolidation maintains the ability to connect various function modules while simplifying the overall main board structure.

Inventive Principle:
Principle #5Merging (Combining)

3Adaptability or versatility

If the main board size is increased to accommodate electrical connectors, then connection capacity is sufficient, but the device loses lightweight and thinning capability

Engineering Contradiction:
Improveconnection capacityVSAvoiddevice weight
Core Design Contradiction:
Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The patent merges connector functionality into the main board itself, eliminating the need for separate connector components that would add weight. The integrated pads provide sufficient connection capacity for all function modules while maintaining a compact, lightweight design that preserves the device's thinning capability.

Inventive Principle:
Principle #5Merging (Combining)

4Reliability

If traditional electrical connectors with large structural sizes are used, then reliable signal transmission is achieved, but space for other function modules is reduced

Engineering Contradiction:
Improvesignal transmission reliabilityVSAvoidmounting space for function modules
Core Design Contradiction:
ReliabilityVSArea of stationary object

Solution Approach 1:

The patent extracts the heavy, space-consuming connector components and replaces them with lightweight integrated pads on the main board. This extraction of unnecessary intermediate components maintains reliable signal transmission through direct pad-to-flexible circuit board connections while freeing up significant mounting space for other function modules.

Inventive Principle:
Principle #2Taking out (Extraction)

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 space utilization and improves lightweight and thinning capabilities of electronic devices by reducing the size of the control main board, increasing mounting space and functional effects of modules.

Implementation Method 1

the pins of the second connecting terminal are connected to the pads by a laser welding process

Methodology Applied
Scientific EffectLaser welding: Laser Beam Welding

Data Source

PatentEP3758455B1Electronic device
Publication Date: 2026.04.08 BEIJING XIAOMI MOBILE SOFTWARE CO LTD
  • EP3758455B1 patent drawingFigure 1
  • EP3758455B1 patent drawingFigure 2~3

AI summary

The present disclosure relates to an electronic device (2). The electronic device (1) can include a device body (11), a control main board (12), and at least one function module (13) mounted in the device body (11). The control main board (12) of the electronic device (1) is provided with a pad group (122) and a flexible printed circuit board (123), such that each pad group (122) is electrically connected to the corresponding function module (13) by the flexible printed circuit board (123). The first connecting terminal (1231) of the flexible printed circuit board (123) is electrically connected to the function module (13), and the pins (1232a) of the second connecting terminal (1232) of the flexible printed circuit board (123) correspond to and electrically cooperate with the pads (1221) of the pad group (122).