How to Avoid Edge Burrs During the Die-Cutting Process of Membrane Switches
Edge burrs are a common defect in the die-cutting of membrane switches,which can damage the adhesive layer,reduce sealing performance,and even cause short circuits in the internal circuit.To completely avoid or minimize edge burrs,the solution needs to cover mold optimization,material matching,process parameter adjustment and post-processing improvement.The specific methods are as follows:
1.Optimize Die-Cutting Mold Design and Manufacturing
The quality of the die-cutting mold is the core factor that determines whether burrs are generated.High-precision molds can directly reduce the probability of edge burrs.
Choose the right mold type
For thin film materials(thickness<0.15mm)such as PET/PC top panels and circuit substrates,use laser-cut precision steel rules instead of ordinary die-cutting blades.Laser cutting can make the blade edge smooth and sharp,avoiding the"tooth-shaped"burrs caused by the uneven edge of the ordinary blade.
For multi-layer composite materials(thickness>0.3mm),use engraved molds(CNC precision molds).The mold gap can be controlled within±0.01mm,which ensures that each layer of material is cut off at one time without tearing.
Sharpen the mold blade reasonably
The blade of the die-cutting mold should be kept sharp.For new molds,perform a passivation treatment on the blade edge(edge radius 0.02–0.05mm)to avoid excessive sharpness that causes material tearing;for used molds,sharpen them regularly when the blade wear exceeds 0.1mm.
Ensure the blade is perpendicular to the mold base(verticality error<0.02mm).A tilted blade will cause uneven force during die-cutting and produce burrs on one side of the edge.
Set a reasonable mold clearance
The gap between the upper die and the lower die should match the total thickness of the membrane switch material.The general gap is 10%–15%of the material thickness.For example,for a composite material with a thickness of 0.2mm,the mold gap should be controlled at 0.02–0.03mm.Too large a gap will cause incomplete cutting,while too small a gap will squeeze the material and produce burrs.
2.Match Die-Cutting Materials and Adjust Lamination Structures
Different membrane switch materials have different toughness and cutting characteristics,and reasonable material matching can reduce burr generation.
Select materials with good cutting performance
For the top panel,choose biaxially oriented PET films with uniform thickness and tight molecular structure.Avoid using low-quality PET films with uneven thickness or loose texture,which are prone to burrs during die-cutting.
For the adhesive layer,use acrylic double-sided adhesive with a release film with a smooth surface.The release film can reduce the friction between the adhesive and the mold during die-cutting,preventing the adhesive from sticking to the blade and forming burrs.
Optimize the multi-layer lamination structure
When laminating multi-layer materials(top panel+adhesive+circuit layer+substrate),ensure that the layers are tightly bonded without air bubbles.Air bubbles will cause uneven stress during die-cutting and lead to edge burrs.
For materials with large differences in hardness(e.g.,rigid FR-4 substrate+flexible PET panel),add a buffer layer(e.g.,0.05mm thin PET film)between the hard and soft layers to balance the cutting force.
3.Adjust Die-Cutting Process Parameters Precisely
Reasonable process parameters are the key to avoiding burrs,and the core is to control the cutting force,speed and temperature.
Control die-cutting pressure and speed
Determine the optimal cutting pressure according to the material thickness.The pressure should be sufficient to cut through all layers of material without excessive extrusion.For example,for a 0.25mm composite material,the pressure is generally controlled at 0.8–1.2 MPa.Excessive pressure will cause material deformation and burrs;insufficient pressure will lead to incomplete cutting.
Use a low-speed,stable die-cutting speed(10–20 m/min for roll-to-roll die-cutting).High speed will cause the blade to rub against the material,generating heat and softening the material,which is prone to burrs.
Maintain a stable die-cutting temperature
The die-cutting environment temperature should be controlled at 23±2℃,and the relative humidity should be 45%–55%.High temperature will soften the adhesive layer and cause it to stick to the blade,forming burrs;low temperature will make the material brittle and easy to crack.
For heat-sensitive materials(e.g.,TPU films),use cooling die-cutting molds(install cooling channels in the mold base)to reduce the temperature rise during cutting.
4.Improve Post-Die-Cutting Treatment
Even if the die-cutting process is optimized,a small amount of micro-burrs may remain,and post-processing can further remove them.
Adopt deburring processes
For large-sized membrane switches,use a brushing machine with a soft nylon brush to gently brush the edges to remove micro-burrs.The brushing speed should be controlled at 50–80 r/min to avoid damaging the material surface.
For small-sized or high-precision products,use ultrasonic cleaning(frequency 28–40 kHz)to remove burrs and dust at the same time.The cleaning time is 3–5 minutes,which will not affect the electrical performance of the switch.
Perform 90%visual inspection
After die-cutting and deburring,use a magnifying glass(10–20x magnification)to inspect the edges of each product.Reject products with burrs exceeding 0.03mm in height to ensure the consistency of the final product.