Printing Stencil Milling for Solder Paste Precision
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Solution Overview
Problem
Existing methods for producing printing stencils for technical printing, such as SMD circuit boards, face challenges in achieving high precision for indentation size, shape, and positioning, leading to uneven solder paste application and increased reject rates due to low accuracy and material wear.
Innovation Solution
A method involving clamping a raw stencil on a support plate and using a laser beam to cut precise pad openings, followed by milling at speeds below 10,000 rpm to create depressions with high surface roughness, ensuring accurate and flexible stencil production with precise solder paste volume application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed milling is used to work out depressions on the stencil, then productivity is improved, but manufacturing precision deteriorates due to low surface roughness causing uneven solder paste application
Solution Approach 1:
The patent changes the milling speed parameter from high-speed (above 20,000 rpm) to low-speed (below 10,000 rpm) to achieve the desired surface roughness. This parameter change transforms the surface finish quality, enabling solder paste to roll off properly during the printing process while maintaining acceptable productivity levels.
2Manufacturing precision
If low-speed milling is used to achieve high surface roughness, then manufacturing precision is improved, but productivity deteriorates due to slower material removal
Solution Approach 1:
The patent applies partial milling action by removing material only to the extent needed to create the depression and achieve the target surface roughness, rather than over-milling. This allows low-speed milling to be efficient by performing just enough material removal to achieve the desired surface quality without unnecessary time consumption.
3Productivity
If high-speed milling is used, then productivity is improved, but reliability deteriorates due to material tension and waviness in the stencil
Solution Approach 1:
The patent changes the milling speed parameter to low-speed operation, which reduces the mechanical stresses and vibrations that cause material tension and waviness in the thin-walled stencil. This parameter change improves stencil reliability and flatness, ensuring consistent printing quality throughout the stencil's service life.
4Productivity
If conventional milling speeds are used, then productivity is maintained, but manufacturing precision deteriorates due to insufficient surface roughness for proper solder paste application
Solution Approach 1:
The patent implements a specific parameter change by reducing milling speed below 10,000 rpm, which generates sufficient surface roughness through the milling process itself. This roughness enables the solder paste to roll off the stencil surface properly during printing, achieving the desired manufacturing precision for solder paste application.
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 approach allows for precise and uniform solder paste application, reducing inaccuracies and extending stencil lifespan by minimizing material tension and wear, thereby improving the reliability of printed circuit boards.
Implementation Method 1
clamping a raw stencil, possibly cut to a predetermined stencil size from a thin-walled raw sheet metal, on a flat support plate of a clamping table with suction openings or a flat support plate made of porous Stone for level suction of the raw stencil by negative pressure or vacuum
Implementation Method 2
cutting out a plurality of pad openings from the printing stencil in predetermined precise positioning, size and shape by means of a laser beam, i.e. by so-called laser cutting
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to methods for producing a printing stencil for technical printing, comprising the process steps of clamping a raw stencil on a flat support plate with suction openings or a flat support plate made of porous stone for flat suction of the raw stencil by negative pressure, cutting out a plurality of pad openings from the printing stencil in a predetermined precise positioning, size and shape by means of a laser beam, and machining one or more flat recesses in a predetermined positioning, shape, size and/or depth from the clamped printing stencil on at least one side of the printing stencil by milling with a milling tool at speeds below 25,000 min-1, wherein the surface of the recesses machined by milling has a surface roughness with a roughness value of 0.5 µm to 10 µm.Furthermore, the present invention relates to a printing stencil for technical printing, manufactured according to a method according to the present invention.