Stencil Printer Squeegee Force Control via Load Cell Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inconsistent pressure application during the printing of viscous materials like solder paste onto substrates due to inadequate support, variations in spring constant, and friction issues in existing stencil printers, making it difficult to achieve accurate force control.
Innovation Solution
The implementation of a stencil printer with a load cell to measure the force of the squeegee blade against the stencil, coupled with a squeegee blade movement mechanism that includes a pivot plate and angular contact bearings to minimize friction and ensure accurate pressure application, and a controller to display and control the force readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a compression spring is used to provide resistance force for the squeegee blade, then the squeegee blade can apply force to the stencil, but the variations in spring constant make it difficult to determine whether desired pressure is being accurately applied
Solution Approach 1:
The patent replaces the compression spring mechanism with a motor-driven lead screw mechanism. The motor provides controlled rotational motion that is converted to linear motion by the lead screw, enabling precise control and measurement of the squeegee blade force applied to the stencil. This eliminates the variability inherent in spring constants while maintaining the necessary force application capability.
2Ease of operation
If linear bearings are used to support the movable plate, then the squeegee blade can move vertically, but the unwanted friction created by the linear bearings makes it difficult to determine whether desired pressure is being accurately applied
Solution Approach 1:
The patent eliminates the linear bearing mechanism entirely by using a motor-driven lead screw system. The lead screw provides both the vertical movement guidance and the force application mechanism in one integrated system. This removes the friction introduced by linear bearings while maintaining smooth vertical movement capability through the threaded engagement between the lead screw and lead nut.
3Adaptability or versatility
If the squeegee blade is made flexible to accommodate substrate variations, then the printing process can adapt to different conditions, but the spring constant of the squeegee blade itself affects the force upon which the blade engages the stencil
Solution Approach 1:
The patent makes the squeegee blade flexible by mounting it on a pivot plate that allows angular adjustment. This enables the blade to adapt to substrate variations and maintain contact across the stencil surface. The flexibility is achieved through the pivot mechanism rather than blade material compliance, separating the adaptation function from the force application function.
Solution Approach 2:
The patent incorporates a load cell to measure the actual force applied by the squeegee blade to the stencil. This feedback mechanism allows the control system to monitor and adjust the motor-driven lead screw to maintain consistent force despite blade flexibility or substrate variations, ensuring accurate pressure control throughout the printing process.
4Device complexity
If the support tooling is designed to be simple, then the device complexity is reduced, but the inadequate support of the circuit board causes inconsistent pressure application
Solution Approach 1:
The patent uses load cell feedback to monitor and ensure consistent pressure application regardless of support tooling simplicity. The load cell measures the actual force applied to the stencil, allowing the control system to compensate for any inconsistencies caused by the support structure, thereby maintaining reliable pressure control without requiring complex support tooling.
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 solution provides precise and consistent pressure application, enhancing the accuracy of the printing process by directly measuring and controlling the force applied by the squeegee blade, thus improving the reliability of viscous material deposition on substrates.
Implementation Method 1
The connector may comprise a load cell configured to measure force of the squeegee blade against the stencil
Implementation Method 2
a squeegee blade movement mechanism that includes a pivot plate and angular contact bearings to minimize friction
Data Source
AI summary
A stencil printer includes a frame, a stencil coupled to the frame, a substrate support coupled to the frame to support a substrate in a print position, and a print head, coupled to the frame, to deposit and print viscous material over the stencil. The print head may include a squeegee blade configured to engage the stencil, a squeegee blade mount configured to house the squeegee blade, a squeegee blade movement mechanism configured to move the squeegee blade mount in a z-axis direction from a raised position in which the squeegee blade is spaced from stencil and a lowered position in which the squeegee blade engages and applies a force on the stencil, and a connector configured to pivotally connect the squeegee blade mount to the squeegee blade movement mechanism. The connector may include a load cell configured to measure force of the squeegee blade against the stencil. Other embodiments and related methods are further disclosed.