Captive Screw PCB Assembly Fixture Alignment

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Solution Overview

Problem

Conventional methods for assembling captive screws to printed circuit boards (PCBs) are prone to errors due to manual alignment challenges, leading to potential deviation or skewing of the sleeve flange within the through holes, which complicates efficient assembly, especially when using surface mount technology.

Innovation Solution

A packaging method involving a fixture to clamp the sleeve, a tool for precise alignment, and soldering to secure the sleeve flange within the PCB through holes, ensuring accurate and secure attachment without deviation or skew.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If manual alignment is used to position the captive screw above the through hole, then the assembly process can be performed, but positioning accuracy deteriorates due to manual error

Engineering Contradiction:

Improvemanual positioningVSAvoidalignment accuracy

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent introduces a positioning fixture as an intermediary tool between the manual operator and the captive screw. The fixture includes a positioning hole that receives the captive screw and guides it into accurate alignment with the through hole on the PCB, eliminating manual positioning errors while maintaining ease of operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the manual mechanical positioning system with a tool-based mechanical system. The positioning tool provides precise alignment through its structured geometry (positioning holes and guide features), substituting the imprecise human hand-eye coordination with a deterministic mechanical guidance system.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If the captive screw is individually picked and assembled, then assembly can be performed, but productivity deteriorates due to manual handling of each screw

Engineering Contradiction:

Improveindividual assemblyVSAvoidassembly efficiency

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The patent merges multiple individual assembly operations into a single integrated process. The positioning fixture allows multiple captive screws to be positioned and assembled simultaneously or in rapid succession, combining what would otherwise be separate pick-and-place operations into one efficient workflow that dramatically improves productivity.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If downward force is applied to press the flange into the through hole, then the captive screw can be assembled, but positioning accuracy deteriorates due to deviation and skewing

Engineering Contradiction:

Improveassembly processVSAvoidflange alignment

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent performs preliminary alignment through the positioning fixture before the actual assembly force is applied. The fixture pre-positions the captive screw in perfect alignment with the through hole, so that when downward force is later applied to press the flange in, the alignment is already established and cannot be compromised by the assembly force.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The positioning fixture acts as a cushioning mechanism that protects against alignment errors during the forceful assembly process. By establishing alignment beforehand through the fixture's guide features, any subsequent forces applied during assembly cannot cause deviation or skewing of the flange relative to the through hole.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

This method enables easy, accurate, and efficient assembly of captive screws to PCBs by ensuring the sleeve flange is firmly fitted in the through holes without deviation or skew, enhancing the reliability of the assembly process.

Implementation Method 1

allowing the molten solder layer to cool down to room temperature and become hardened again

Methodology Applied

Scientific EffectCooling: Cooling

Implementation Method 2

heating and melting the layer of solder and then allowing the molten solder layer to cool down to room temperature and become hardened again

Methodology Applied

Scientific EffectPhase change: Phase Change

Data Source

PatentUS8291583B2Packaging method for assembling captive screw to printed circuit board

Publication Date: 2012.10.23 WANG TING JUI

AI summary

A packaging method for assembling a captive screw to a printed circuit board (PCB) includes the steps of providing a captive screw having a screw head, a threaded shank and a sleeve; pressing a fixture toward the screw head for a part of the threaded shank to exposed from a distal end of the sleeve, and then clamping the fixture on the sleeve; providing a PCB having through holes and a layer of solder provided thereon; using a tool to pick up the fixture and the captive screw and align the threaded shank with one through hole on the PCB; releasing the fixture and the captive screw from the tool for a flange at the distal end of the sleeve to extend into the through hole; heating, melting and then cooling to harden the solder layer, so that the sleeve is fixedly held to the PCB; and removing the fixture.