The Process Differences Between QDR and FR

1. Quick Drain and Rinse (QDR)

QDR is a cleaning method based on discrete, periodic emptying and injection. The process is not continuous but instead consists of a complete operational cycle—comprising "Dump," "Fill," and (optional) "Stand"—which is repeated multiple times to achieve the desired cleaning effect.

Detailed Explanation of the Mechanism:

• Dump Phase: The existing liquid inside the cavity is rapidly and thoroughly expelled within a short time—typically just a few seconds. This step is critical for achieving a "hard switch," designed to instantly eliminate any residual buildup of the old liquid.
• Fill Stage: Immediately after emptying, fresh ultrapure water is injected into the chamber to restore it to the preset liquid level. The water-injection process is typically slightly slower than the draining phase, ensuring smooth flow and minimizing secondary agitation of particles.
• The "emptying-injection" process described above is repeated 3 to 6 cycles. Each cycle essentially serves as a "reset" of the liquid environment within the chamber, theoretically minimizing the prolonged coexistence and mixing of old and new liquids inside the cavity.

Typical parameters:

Drain time: 5–15 seconds

Watering time: 10–30 seconds

Number of repetitions: 3–6 times

Advantage: Each emptying cycle achieves a "hard switch," theoretically preventing the prolonged coexistence of old and new liquids.

Disadvantage: If draining is not thorough, residual liquid at the bottom may re-mix into the next cycle.

2. Overflow Cleaning (FR)

FR is a cleaning method based on continuous inflow and overflow. Throughout the entire cleaning process, ultrapure water is continuously injected into the chamber, while an overflow device positioned above the chamber ensures that the liquid level remains constantly full, allowing the incoming fresh water to "push" the old liquid out of the system.

Detailed Explanation of the Mechanism:

• Continuous injection: Fresh ultrapure water is introduced at a constant flow rate (e.g., 20–60 L/min) from the bottom or side wall of the chamber, creating a stable flow field.
• Continuous overflow: The cavity is equipped with an opening at the top. When the liquid level exceeds the height of the overflow weir, the liquid—contaminated old fluid mixed with impurities—will continuously spill out of the system, thereby maintaining dynamic equilibrium.
• The replacement mechanism: At its core, the cleaning process combines "push-flow displacement" with "dilution." Ideally, fresh water acts like a piston, pushing the old water out; however, due to the presence of dead zones or non-ideal flow patterns in the actual flow field, pollutant removal within these dead zones primarily relies on slow molecular diffusion and convection.

Typical parameters:

Flow rate: 20–60 L/min

Time: Continuous 2–10 minutes

Objective: Complete 3–5 volume replacements (e-fold)

Advantages: Stable flow field, ideal for scenarios with high requirements for controlling secondary particle contamination.

Disadvantage: Liquid replacement in the dead zone relies on diffusion and slow convection, resulting in lower efficiency.

Kexinwei Company – Leading the Innovation in Semiconductor Cleaning Technology

For more technical details, please consult our technical advisor: 13861996325!

▲ Technical Consulting ▲ Follow Kexinwei's WeChat Official Account