Slurry reprocessing, especially when it involves silicon wafer slicing, is a precise business. As one of the pioneers in the slurry reprocessing industry, CRS has had many years to refine and perfect effective slurry management. Through innovative technology and a highly experienced staff, CRS provides customized slurry reprocessing solutions to optimize our customers wafering operations. The result is an extended team of experts working on site to deliver the highest quality cutting materials for the silicon wafer industry.
Slurry Proven Process
The CRS process for recovering spent slurries is a proprietary method incorporating diluents and mechanical processes, devoid of chemicals, to facilitate the separation of recoverable grit and carrier. Our process, developed over years of refinements dating back to the introduction of slurry, produces higher yields and better recovery rates that directly impact a company’s bottom line.
Step 1: During the first step, a diluent compatible with the carrier and grit is mixed with the slurry. Once mixed, the slurry blend is heated to a temperature that has been carefully predetermined from laboratory pilot studies. After heating, the mixture is processed through a unique centrifuge built to CRS specifications. This step extracts the good grit particles that are large enough to still be effective in the cutting or grinding process.
Step 2: The remaining material moves to a process designed to recover the carrier. Using our proprietary centrifuge technology, the spent grit and waste kerf is first separated from the reusable carrier.
Step 3: The system then recovers the carrier. The remaining material from this process is a small amount of waste kerf. Depending on disposal method, the consistency of this waste material can be adjusted.
Step 4: The final phase recombines the recovered grit and carrier with virgin grit and carrier to make finished slurry. The virgin makeup carrier and grit is added to replenish the loss of volume that was unusable and removed in reprocessing. Blend tanks with load cells and specific gravity sensors monitor the batch weight and adjust specific gravity to achieve target values for batch size and density. In-line density instrumentation is used as the controlling feature of the blending process. The finished slurry is sent to holding tanks where it typically will be delivered directly to the saws through a slurry distribution loop designed by CRS.
The percentage of recovery varies from slurry to slurry, but typical results for every pound of slurry processed are greater than 85% for both the grit and the carrier. The actual amount of recovered grit reused is a function of the wafering requirements. For oil-based slurries, the recovery of the cleaning solvents used to rinse wafers and equipment is typically greater than 90%.