Thin Circuit Board Wall for Solder Bridge Prevention

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Solution Overview

Problem

The challenge is to prevent solder bridges and ensure a sufficient solder fillet size in thin circuit boards with closely spaced internal terminals, particularly in miniaturized hard disk drives where the distance between terminals is reduced, while maintaining reliable connections.

Innovation Solution

A thin circuit board design featuring a metal support layer, base insulating layer, wiring layer, and a cover insulating layer with internal terminals that include a wall to contain solder material, preventing solder bridges and ensuring an adequate solder fillet size, even with reduced terminal spacing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the distance between adjacent internal terminals is reduced to accommodate more terminals in miniaturized hard disk drives, then the number of connections increases, but solder bridges are more likely to occur

Engineering Contradiction:

Improvenumber of connectionsVSAvoidsolder bridge prevention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent divides the terminal area into separate regions by introducing partition walls between adjacent internal terminals. These walls segment the soldering space, preventing solder material from flowing across multiple terminals and creating solder bridges, while still allowing close spacing for increased connection density

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The partition walls act as intermediary structures between adjacent terminals. These walls are positioned to block solder material flow paths while allowing the terminals themselves to remain closely spaced, thus mediating between the need for high density and the need to prevent solder bridges

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the diameter of micro solder balls is reduced to prevent solder bridges, then solder bridge generation is suppressed, but the solder fillet size becomes insufficient for reliable connection

Engineering Contradiction:

Improvesolder bridge suppressionVSAvoidsolder fillet size

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The partition walls serve as intermediary structures that redirect solder material flow. Instead of reducing solder ball size, the walls guide the solder to form fillets at the intended connection locations while preventing lateral flow that would cause bridges, thus maintaining both small ball diameter and adequate fillet size

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical approach of reducing solder ball diameter with a structural approach using partition walls. Rather than changing the soldering process parameters (ball size), the solution modifies the terminal structure to control solder flow behavior, achieving the same goal through a different mechanism

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If the number of internal terminals is increased to support multi-functionalized head suspension, then connection capability improves, but the area occupied by terminals increases

Engineering Contradiction:

Improveconnection capabilityVSAvoidterminal area

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The partition walls segment the terminal region into multiple discrete zones, allowing many terminals to be packed into a compact area. This segmentation enables increased connection capability while minimizing the overall area occupied, as the walls define clear boundaries that allow dense packing without excessive spacing

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different structural qualities to different regions. Partition walls are introduced only where needed to separate adjacent terminals, while maintaining open spaces where terminals are spaced apart. This localized approach to structuring enables high density where necessary while preserving ease of manufacture and soldering where required

Inventive Principle:

Principle #3Local quality

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

The solution effectively prevents solder bridges and ensures a sufficient solder fillet size for reliable connections by containing the solder material with a wall on adjacent internal terminals, maintaining connection integrity even with reduced terminal spacing.

Implementation Method 1

a wall provided for the solder material on at least any one of adjacent internal terminals of the internal terminals

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Implementation Method 2

each one internal terminal of the internal terminals used to be solder-bonded to a corresponding external terminal through solder material

Methodology Applied

Scientific EffectSoldering: Soldering

Data Source

PatentUS10021781B2Thin circuit board having wall for solder material

Publication Date: 2018.07.10 NHK SPRING CO LTD

AI summary

A thin circuit board such as a flexure has a metal support layer forming a substrate, a base insulating layer provided on the metal support layer, a wiring layer being wiring traces provided on the base insulating layer, a cover insulating layer covering the wiring layer, internal terminals provided to the respective wiring traces and sequentially arranged side by side, each one internal terminal of said internal terminals used to be solder-bonded to a corresponding external terminal through solder material, and a wall provided for the solder material on at least any one of adjacent internal terminals of said internal terminals.