The vacuum suction cup grinder is the core equipment for precision grinding
of quartz ceramic substrates (used for semiconductor packaging and photovoltaic
modules), responsible for processing the substrate to a specified thickness
(tolerance ± 0.01mm) and ensuring flatness (≤ 0.005mm/m), directly affecting the
quality of subsequent coating and cutting processes of the substrate. If there
is a large deviation in flatness (exceeding 0.01mm/m) or edge breakage (with a
width exceeding 0.2mm), it will result in a substrate scrap rate of over 15% and
significantly increase production costs. Based on the characteristics of quartz
ceramics with a Mohs hardness of 7-8 and high brittleness, a three-step
troubleshooting method is summarized to quickly restore the precision grinding
performance.
Step 1: Optimize the vacuum suction cup adsorption and fixture accuracy -
Basic guarantee for controlling flatness
The uneven suction of suction cups and insufficient precision of the tabletop
are the core reasons for flatness deviation.
Imbalance or leakage of suction cup suction force: The suction cup partition
suction pressure deviation exceeds 0.02MPa, and the local stress on the
substrate is uneven, resulting in deformation during grinding; Scratches and
pores on the suction cup surface cause air leakage, resulting in a decrease in
adsorption force (below 0.06MPa) and easy displacement of the substrate. Select
porous ceramic vacuum suction cups and divide them into 3-4 adsorption zones
according to the substrate size. Adjust the pressure deviation of each zone to ≤
0.01MPa through a pressure regulating valve; Repair the scratches on the surface
of the suction cup with grinding paste, seal the pores, ensure that the
adsorption force is stable at 0.08-0.1MPa, and the substrate is not loose after
adsorption.
Precision degradation or positioning deviation of suction cup tabletop: The
wear of the tabletop flatness exceeds 0.003mm/m, directly causing the substrate
grinding reference to deviate; Positioning pin wear exceeds 0.01mm, substrate
clamping position deviation, and uneven edge grinding. Calibrate the suction cup
table with a laser interferometer, and grind and repair it when it exceeds the
tolerance, ensuring that the flatness is ≤ 0.002mm/m; Replace the high-precision
positioning pin, use a dial gauge to detect the edge positioning deviation of
the substrate after clamping, and control it within ± 0.005mm.
Step 2: Calibrate grinding parameters and wheel configuration - core control
to reduce edge collapse
Improper grinding wheel characteristics, grinding speed, and feed rate can
exacerbate edge chipping and flatness issues.
Poor adaptability or wear of grinding wheels: ordinary corundum grinding
wheels are used, which have insufficient hardness and are prone to abrasive
particle detachment. The grinding force fluctuates greatly, and the edges of the
substrate are prone to cracking; The grinding wheel has coarse grain size
(<800 mesh), deep grinding marks, and large flatness deviation; The end face
runout of the grinding wheel exceeds 0.002mm, causing vibration during grinding.
Replace the diamond resin bonded grinding wheel (particle size 1000-1200 mesh,
medium soft hardness) to adapt to the brittle and hard characteristics of quartz
ceramics; Calibrate the grinding wheel with a dynamic balancer, and control the
end face runout within ± 0.001mm. Sharpen the grinding wheel for every 50
substrates ground.
Imbalance of grinding parameters: When the linear velocity of the grinding
wheel is below 25m/s, the friction between the abrasive particles and the
substrate intensifies, and the edges are prone to breakage; Above 40m/s,
vibration is enhanced and flatness deviation is large; If the feed rate exceeds
0.005mm/revolution and the grinding load is too high, the substrate is prone to
stress cracking. By adjusting the parameters through a frequency converter, the
linear speed of the grinding wheel is stabilized at 30-35m/s, and the feed rate
is controlled at 0.002-0.003mm/revolution; Adopting the "segmented grinding"
mode, coarse grinding (feed rate of 0.004mm/rev) removes most of the excess,
fine grinding (feed rate of 0.002mm/rev) ensures accuracy, and the edge area is
individually fine tuned to a feed rate of 0.001mm/rev.
Step 3: Adapt substrate characteristics and cooling protection - avoid
defects at the source
Insufficient cooling and lubrication, substrate pretreatment, and
environmental vibration can affect grinding stability.
Insufficient cooling and lubrication or poor medium adaptation: The coolant
flow rate is below 30L/min, which cannot timely remove the grinding heat and
cause local thermal stress cracking of the substrate; Insufficient lubricity of
the coolant leads to adhesion of abrasive particles, resulting in a sudden
increase in grinding force. Select quartz ceramic specific grinding fluid
(containing extreme pressure additives, viscosity 5-8mm ²/s), ensure a stable
flow rate of 40-50L/min, and install directional nozzles to accurately cover the
grinding area and substrate edge with the coolant; Regularly filter the coolant
(filtration accuracy ≤ 5 μ m) to avoid impurities scratching the substrate.
Edge defects or environmental interference on the substrate: there are burrs
and microcracks on the edge of the substrate blank, which are prone to expand
into edge collapse during grinding; The workshop floor vibration exceeds
0.005mm, affecting the accuracy of the grinder operation. Before grinding, use a
diamond chamfering tool to chamfer the edge of the substrate blank at 0.2 × 45 °
to remove burrs and microcracks; Install shock-absorbing pads at the bottom of
the grinder, away from vibration sources such as stamping and cutting, to ensure
that the environmental vibration during grinding is ≤ 0.003mm.
Daily maintenance should pay attention to: checking the suction force of the
suction cup, the condition of the grinding wheel, and the flow rate of the
coolant every day; Calibrate grinding parameters, wheel dynamic balance, and
suction cup flatness weekly; Clean the cooling system monthly and replace aging
seals; Quarterly inspection of grinding machine guide rail accuracy and
lubrication maintenance. By implementing the above measures, the flatness of the
substrate can be reduced to ≤ 0.004mm/m, the edge breakage rate can be lowered
to below 3%, and the finished product qualification rate can be significantly
improved. If there are still problems, it is recommended to contact the
manufacturer to optimize the grinding wheel formula and suction cup adsorption
scheme to match the precision grinding needs of quartz ceramic substrates.