Flex Circuit for BGA Pin Access Without Height Increase

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Solution Overview

Problem

Existing solutions for accessing pins of a ball grid array (BGA) component after mounting on a printed circuit board are costly and complicated, often requiring custom PCBs and manual methods like deconstruction or hand wiring, which are not suitable for production environments and fail to detect design faults effectively.

Innovation Solution

A flexible circuit is used to access pins of the BGA component by mounting it between the BGA and the PCB, featuring conductive leads and dielectric film layers with contact holes to electrically connect with solder balls, allowing for monitoring and correction of design faults without adding height to the surface-mount package.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a custom PCB is used to access pins of a BGA component, then pin accessibility is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improvepin accessibilityVSAvoidPCB complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The solution divides the access function into two parts: the standard PCB for normal operation and a separate flex circuit for testing/access. This segmentation allows the main PCB to remain simple while adding access capability through the flexible circuit that can be positioned as needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A flex circuit serves as an intermediary component between the BGA component and the standard PCB. This intermediate element provides the necessary access path without requiring modification of the original PCB design, thus maintaining simplicity while enabling functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If manual deconstruction or hand wiring methods are used, then pin access is achieved, but productivity and manufacturing efficiency deteriorate

Engineering Contradiction:

Improvepin access capabilityVSAvoidmanufacturing efficiency

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The flex circuit is pre-configured with conductive leads and contact holes during manufacturing, establishing the access path in advance. This preliminary preparation eliminates the need for manual deconstruction or hand wiring during production, as the access infrastructure is already in place.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The flex circuit is designed to be self-installing through standard mounting procedures. The component provides its own access functionality without requiring external manual intervention, thus maintaining high manufacturing efficiency while enabling pin access.

Inventive Principle:

Principle #25Self-service

3Difficulty of detecting and measuring

If existing access methods are used, then pin evaluation is enabled, but reliability of the BGA component may be compromised

Engineering Contradiction:

Improvedesign fault detectionVSAvoidBGA component reliability

Core Design Contradiction:

Difficulty of detecting and measuringVSReliability

Solution Approach 1:

The flex circuit acts as a non-intrusive intermediary that accesses BGA pins without requiring physical contact or modification of the BGA component itself. This indirect access method enables fault detection while preserving the integrity and reliability of the original component.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The flexible circuit provides a thin, adaptable interface that can conform to the narrow space between the BGA component and PCB without applying excessive force or interference. This flexibility allows access while minimizing mechanical stress on the BGA component, thereby maintaining reliability.

Inventive Principle:

Principle #30Flexible shells and thin films

4Ease of operation

If access components are added to the package, then pin accessibility is improved, but package height increases

Engineering Contradiction:

Improvepin accessibilityVSAvoidpackage height

Core Design Contradiction:

Ease of operationVSLength of stationary object

Solution Approach 1:

Instead of adding vertical height to access pins, the flex circuit utilizes the horizontal plane and the narrow gap dimension between the BGA component and PCB. This dimensional approach allows access functionality without increasing the overall package height, as the circuit routes through the available lateral space.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The flexible circuit is designed as a thin film that can fit within the narrow 250-micron gap between the BGA component and PCB. This thin-profile design enables pin access while maintaining a compact package height, as the access path does not extend vertically beyond the existing component boundaries.

Inventive Principle:

Principle #30Flexible shells and thin films

Data Source

PatentUS10269696B2Flex circuit for accessing pins of a chip carrier

Publication Date: 2019.04.23 INTEL CORP

AI summary

Flexible circuits mountable in a standoff region between a chip carrier, e.g., a ball grid array (BGA) component, and a printed circuit board (PCB) of a surface-mount package are described. In an example, a flexible circuit includes holes to receive pins, e.g., solder balls, of the BGA component, and one or more conductive leads electrically connected to respective solder balls within the holes. The conductive leads may interconnect several solder balls within the standoff region, and may be electrically accessible through a test pad located laterally outward from the standoff region. Electrical signals may be monitored or driven through the test pad, and thus, the flexible circuit may be used as a debug tool for detecting and or correcting a design fault of the surface-mount package.