Spring-Tensioned Stencil Frame for Uniform Foil Tension
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Solution Overview
Problem
Existing stencil frames for uniform tensioning of stencil foils in solder paste application are costly and prone to defects due to the need for complex, tightly manufactured metal components and require cumbersome adjustment mechanisms, leading to issues like solder bridges and skips during SMD circuit production.
Innovation Solution
A stencil frame composed of decomposable corner and edge elements with spring-based tensioning devices, where corner elements have mutually perpendicular guiding profiles and edge elements have uniaxial reception profiles, allowing for adjustable and uniform tensioning without pneumatic devices or mechanical gearing, reducing material costs and weight while maintaining high tension capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pneumatic or mechanically geared tensioning systems are used, then uniform tensioning capability is achieved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent replaces complex pneumatic or mechanically geared tensioning systems with a simple spring-based mechanical system. Each tensioning device uses a spring element that directly applies tensioning force to the stencil foil through basic mechanical components, eliminating the need for pneumatic actuators, gears, or complex adjustment mechanisms while maintaining uniform tensioning capability across the stencil frame
Solution Approach 2:
The tensioning system is divided into multiple independent tensioning devices distributed across the stencil frame. Each tensioning device operates autonomously with its own spring element, allowing localized tensioning control without requiring a centralized complex mechanism. This segmentation simplifies the overall system while achieving uniform tension distribution through multiple simple units working in parallel
2Manufacturing precision
If tightly manufactured metal components are used, then tensioning precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent achieves precise tensioning control through adjustable spring pre-compression parameters rather than requiring tight manufacturing tolerances on metal components. The spring force can be easily adjusted by modifying the pre-compression distance, allowing precise tensioning calibration without expensive precision machining. This parameter-based control is more cost-effective than relying on tight component manufacturing tolerances
Solution Approach 2:
The patent uses standardized, simple metal components with basic geometric shapes rather than complex tightly-toleranced parts. The guiding profiles and mounting features use conventional manufacturing tolerances, while the critical tensioning function is achieved through the spring parameter adjustment. This local quality approach concentrates precision requirements on easily adjustable parameters rather than on difficult-to-manufacture component dimensions
3Reliability
If adjustable tensioning mechanisms are incorporated, then tension uniformity is improved, but ease of operation deteriorates due to cumbersome adjustment procedures
Solution Approach 1:
The spring-based tensioning devices are pre-compressed to the desired tension level during assembly or initial setup. Once pre-adjusted, the system maintains uniform tension automatically without requiring frequent manual adjustments during operation. The spring's elastic properties provide self-regulating tension that compensates for minor variations in stencil foil tensioning requirements, reducing the need for operational adjustments
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 provides a cost-effective, lightweight, and robust stencil frame that maintains uniform tension, reducing the risk of solder defects and enabling efficient solder paste application with adjustable tensioning forces up to 120N/cm, thus improving the reliability and efficiency of SMD circuit production.
Implementation Method 1
Each tensioning device has at least one elastic element
Implementation Method 2
spring-based tensioning devices
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Stencil frames for tensioning stencils of an angular shape are provided. The stencil frame comprises corner elements (2), edge elements (1), fastening elements (13) and tensioning devices with a tensioning device being associated with each edge element (1). The corner elements (2) each have two, mutually perpendicular, guiding profiles (12) which joined at an intersection of their axes and the edge elements (1) each have a uniaxial reception profile (11). Each reception profile (11) is connectable to two guiding profiles (12) by loose fit. Each tensioning device has at least one elastic element (5) and connects between two neighbouring corner elements (2). A line of force exerted by each tensioning device is parallel to the axis of its corresponding reception profile (11).