UFC-1661 MultiFlo MFC by UNIT Instruments | 1660 Series Digital

UFC-1661 UNIT Instruments 1660 Series MultiFlo Digital Mass Flow Controller

UFC-1661 is a MultiFlo digital mass flow controller from UNIT Instruments. It belongs to the 1660 Series. You can reprogram gas type and range right on site. Therefore, one part covers many recipes. Moreover, this saves stock cost and setup time. In addition, the dual connector design keeps old tools running. Consequently, upgrades stay simple and cheap. Above all, the field-proven MultiFlo platform cuts spare-part counts. Similarly, the wide flow span trims the number of stocked part numbers.

Core Highlights

• Flow range: 3 sccm to 30 slm (N2 equivalent).
• MultiFlo range: Program full scale from 33% to 100% of max range.
• Accuracy: ±1% of setpoint above 35% FS. ±0.35% FS below 35% FS.
• Calibration: 32-point table per gas. Backed by a 3-sigma guarantee.
• Response: 1 second fast start per SEMI E17-91. Soft start ramps at 20% per second.
• Gas support: Unlimited process gases. Factory N2-calibrated.
• Auto-zero: Standard on digital models. Zero drift stays at or under 0.6% FS per year.

Technical Data Tree

• Brand: UNIT Instruments
  • Model: UFC-1661
  • Series: 1660 Series (MultiFlo Digital, RS-485 + Analog)
• Flow
  • Full-scale range: 3 sccm to 30 slm (N2 equivalent)
  • MultiFlo programmable full scale: 33% to 100% of max range
  • Control range: 2% to 100% FS
• Accuracy and Stability
  • Accuracy: ±1% of setpoint above 35% FS. ±0.35% FS below 35% FS
  • Repeatability: ±0.15% FS per SEMI E56-96
  • Linearity: ±0.5% FS per SEMI E27-92
  • Zero stability: 0.6% FS per year or less, without auto zero
  • Auto-zero: Standard on digital models
  • Temperature coefficient: Zero 0.05% FS per °C. Span 0.1% FS per °C
  • Pressure coefficient: 0.007% reading per psi (N2)
• Response
  • Fast start: 1 second or less per SEMI E17-91
  • Programmable response: Under 1 second up to 20 seconds
  • Soft start: Linear ramp at 20% per second
• Gas Handling
  • Gas type: Unlimited process gases, field-programmable
  • Factory calibration: N2
• Pressure
  • Max operating: 3,500 kPa (500 psi)
  • Proof: 10,500 kPa (1,500 psi)
  • Differential: 6.65 to 350 kPa (50 torr to 50 psid)
• Materials and Seals
  • Wetted materials: 316L SS / K-M43 / 304 / 7Mo
  • Surface finish: 16 micro-inch Ra standard. 10 micro-inch optional
  • Seals: Metal seal (C-seal / W-seal). Kel-F or metal seat
  • Leak integrity: 1 x 10^-10 atm-cc/sec He per SEMI E16-90
• Electrical
  • Interface: Dual connector
  • Analog: 20-pin card edge or 9/15-pin D-sub
  • Digital: RS-485 daisy-chain modular jack
• Power
  • Supply: +15 VDC and -15 VDC, 160 mA max each
  • Consumption: 5 W max
• Valve
  • Type: Proportional electromagnetic (Unit 132 valve)
  • Modes: Normally closed or normally open solenoid
• Environment
  • Heated option: No, standard unit is unheated
  • Operating temperature: 0 to 50 °C (32 to 122 °F)
• Physical
  • Dimensions: Approx. 137 x 127 x 38 mm (HxWxD)
  • Footprint: 1.5 in
  • 1/4 VCR overall length: 124 mm
  • Weight: 1.2 kg (2.65 lbs)
• Compliance
  • Certification: CE certified
  • SEMI: E12, E16, E17, E27, E56 compliant
  • Calibration: NIST-traceable
  • Lifecycle: Current, verified 2026-11

Where the UFC-1661 Fits

• Plasma etch tools: Fast start supports short process steps.
• CVD and EPI reactors: Stable flow helps film uniformity.
• Diffusion furnaces: MultiFlo range change covers many tube sizes.
• Sputtering chambers: Metal seals resist aggressive gases.
• High-purity gas panels: 16 micro-inch finish keeps lines clean.
• Legacy analog tools: Drop-in replacement for older 1660 units.

FAQ

Q: How do I change gas type or full scale on site?

A: Use the MultiFlo digital interface. You set the new gas and range in software. Therefore, no factory trip is needed. In practice, most users finish in minutes. Furthermore, you can save several setups in memory. Consequently, repeat jobs load fast. Besides, no extra hardware is required.

Q: My analog tool has an old 1660 unit. Will this fit?

A: Yes. The UFC-1661 is backward-compatible with analog 1660 tools. It offers a 20-pin card edge and D-sub options. Thus, rewiring stays minimal. Furthermore, the 1.5 in footprint matches older mounts. In addition, the 124 mm VCR length fits tight spaces. Hence, most swaps need no new plumbing. Also, the metal seal suits existing high-purity lines.

Q: Why does response time vary between runs?

A: The response setting is programmable. It spans under 1 second to 20 seconds. Also, check the soft-start ramp. A slow ramp often looks like slow response. Therefore, match the setting to your recipe. Moreover, log the setting per run for clarity. As a result, you spot drift early. Likewise, compare runs on the same gas table.

Q: How do I keep zero drift low?

A: Turn on auto-zero on digital models. Consequently, drift stays at 0.6% FS per year or less. Also watch ambient temperature. Zero shifts 0.05% FS per °C. Hence, stable room temperature helps. Besides, re-zero after long idle periods. Similarly, check zero after gas line work. Finally, keep the unit away from hot exhaust ducts.

Q: What causes a reading offset after a pressure change?

A: The pressure coefficient is 0.007% of reading per psi (N2). Keep differential pressure inside 6.65 to 350 kPa. Then re-zero after big line changes. As a result, this clears most offsets. In addition, check for leaks in the supply line. Also, confirm the regulator holds steady. Meanwhile, watch for sharp pressure spikes at valve open.

Packing List

• One UFC-1661 mass flow controller.
• One connector kit (analog and RS-485).
• One NIST-traceable calibration certificate.
• One compliance document set.