Stencil Printer Print Head Pressure Control
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Solution Overview
Problem
Existing stencil printers face challenges with maintaining consistent pressure and viscosity of solder paste during printing, leading to inefficiencies and increased maintenance due to deformation of squeegee blades and volatile solvent evaporation.
Innovation Solution
A print head with a direct pressure control system, including a chamber with pressure sensors and a motor-driven plunger, maintains desired pressure by averaging pressure readings from multiple sensors and using a flexible membrane to control the discharge of viscous materials like solder paste through a dispensing slot onto a substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a squeegee blade is used to force solder paste through the stencil, then the solder paste is deposited onto the circuit board, but the squeegee blade deforms under pressure causing inconsistent pressure across the print head width
Solution Approach 1:
The patent divides the pressure control function into multiple independent pressure sensors positioned across the width of the print head. Each sensor monitors pressure at its specific location, allowing the system to detect and correct regional variations in pressure caused by squeegee deformation, thereby maintaining consistent pressure across the entire print head width.
Solution Approach 2:
The patent implements a feedback control system where pressure sensors continuously monitor the pressure applied by the squeegee blade at multiple positions. The controller receives this pressure data and adjusts the squeegee drive mechanism in real-time to compensate for deformation, ensuring consistent pressure application across the stencil width throughout the printing process.
2Productivity
If the squeegee traverses the stencil quickly to increase productivity, then more circuit boards can be printed, but the pressure on the solder paste becomes insufficient leading to poor print quality
Solution Approach 1:
The patent employs dynamic pressure adjustment where the squeegee drive mechanism can vary its speed and applied force in real-time based on feedback from pressure sensors. This allows the system to maintain optimal pressure for print quality even when operating at high speeds, as the pressure is actively controlled rather than being a fixed mechanical parameter.
Solution Approach 2:
The feedback control system monitors pressure at multiple positions across the print head and adjusts the squeegee drive accordingly. This ensures that even during high-speed operation, the pressure applied to the solder paste remains within the optimal range for quality printing, preventing both under-pressure and over-pressure conditions.
3Force
If the squeegee applies high pressure to force solder paste through the stencil, then the paste is forced through apertures, but the squeegee blade deforms causing pressure variation
Solution Approach 1:
The patent uses pressure sensors positioned across the width of the print head to provide real-time feedback on the actual pressure being applied to the solder paste. The controller uses this feedback to adjust the squeegee drive mechanism, maintaining the desired high pressure force while compensating for blade deformation to ensure uniform pressure distribution.
Solution Approach 2:
The system dynamically changes operational parameters including squeegee speed, applied force, and positioning based on feedback from pressure sensors. This allows the maintenance of optimal pressure parameters even as mechanical conditions change due to blade deformation during high-force operation.
4Ease of operation
If volatile solvents are allowed to escape from the solder paste, then the paste can be dispensed, but the viscosity of the solder paste changes affecting print quality
Solution Approach 1:
The patent employs an inert or controlled atmosphere environment within the print head chamber to prevent volatile solvents from evaporating from the solder paste. This controlled environment maintains the paste's viscosity consistency while still allowing it to be dispensed through the stencil, resolving the contradiction between dispensability and viscosity stability.
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 ensures consistent pressure and viscosity across the print head width, reducing maintenance and improving printing quality by maintaining optimal pressure and viscosity, enhancing operator flexibility and efficiency.
Implementation Method 1
at least one pressure sensor positioned within the elongate chamber to detect pressure of the viscous material
Data Source
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AI summary
A stencil printer for printing viscous material on an electronic substrate includes a stencil having apertures formed therein, and a print head positioned over the stencil and configured to deposit viscous material within the apertures of the stencil. The print head includes a housing defining an elongate chamber, a source port defining a passage having an inlet positioned to allow viscous material to flow into the elongate chamber, a pair of blades defining a slot that provides an outlet from which viscous material can flow out of the elongate chamber, an elongate plunger movable in the elongate chamber to reduce a volume of viscous material within the elongate chamber, and at least one sensor to detect pressure of the viscous material within the elongate chamber.