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What is SEMI F47?

SEMI F47-0706 (Reapproved 0812) is an industry standard for voltage sag immunity. It says that industrial equipment must tolerate voltage sags, or dips, on the AC mains supply to specific depths and durations. It is such a good and useful standard that many other industries use it, either formally or informally.

Equipment that complies with SEMI F47 is more reliable, and more productive.

SEMI F47 is an industry standard that sets out, in six pages, the requirements for voltage sag immunity in semiconductor fab equipment.


SEMI F47 Industry Endoresements

“Many of our customers require SEMI F47 certification for our machines, and we work with PSL to obtain this certification. It’s always very easy to work with PSL engineers; PSL is always helpful and quick to respond to our queries.”

Mark DeLuca (August 2017)
Axcelis Technologies Inc.

“PSL has been great to work with for F47 testing. They provided information up front to help us prepare the equipment and facilities prior to testing which saved actual time on the tool. The technicians/engineers have been friendly and flexible while on-site. The certificates/reports are detailed and professional and have appeased customers concerns and request regarding F47. I would definitely recommend PSL!!!”

Tara Smithers (September 2017)
ASM America

“It was easy to work with Andreas and his team from PSL. Fast response to request and good technical support during SEMI F47 certification process.”

Hannes Vahldieck (August 2017)
Danfoss Drives

How Expensive is SEMI F47?

In most cases, it is not necessary to add expensive power conditioning devices to the industrial equipment. Instead, F47 testing by companies like Power Standards Lab identifies the weak points, and suggests low-cost or zero-cost solutions. These solutions range from minor changes in power supply configuration, to software delays, to different relay and contractor selection.

Why use SEMI F47?

The voltage sags required by SEMI F47 typically occur about once per month in semiconductor fabs (fabrication facilities) around the world. So industrial equipment that cannot tolerate these sags typically fails, without explanation, about once per month.

A typical SEMI F47 voltage sag (top) and how it affects a power supply (bottom). This problem was fixed by increasing the size of a capacitor, at a cost of a few dollars.

SEMI F47 Contactor Testing Video

Getting started on SEMI F47

If you are a tool manufacturer for the semiconductor industry, and you need to comply with the new SEMI F47 voltage sag immunity standard, we suggest the following steps:

Read our Application Notes on the standard.
You can get them from Power Standards Lab – just fill out our Free Information Pack Request Form with your name and address. Trouble with this link? Call us at +1-510-522-4400, and we’ll take care of it. (You can download a copy of the standard itself from

Learn a little on-line about the standard.
Take a quick look at our free tutorials, and call us with any questions.

Hire us for one day of testing.
For a few thousand dollars, we’ll provide a skilled engineer and specialized test equipment, including a sag generator. In one day at your site, we can typically certify one three-phase tool, and teach your engineers how to do the testing themselves. We’ll even provide standard, fill-in-the-blanks test plans and reports.

Do the subsequent testing yourself.
Buy or rent our sag generators, and test your tools at your convenience with our software.

Give us a call at ++1-510-522-4400, and we’ll be glad to give you a firm, fixed-price quotation for getting started on SEMI F47 compliance.

Sag immunity testing at semiconductor plants
We specialize in on-site voltage sag immunity testing at your semiconductor plant.
Our lab is fully equipped for power quality immunty testing.
Or you can send your smaller equipment to us for power quality testing in our lab.

SEMI F47 for Tool Manufacturers and End-Users

Stricter Enforcement of SEMI F47 throughout SEMI Fabs in 2017 and 2018

Voltage Sag Immunity for semiconductor manufacturing tools, sub-systems and components. Every modern semiconductor manufacturing tool can be sensitive to brief disturbances on the AC power mains. Electrical systems are subject to a wide variety of power quality problems which can interrupt production processes, affect sensitive equipment, and cause downtime, scrap, and capacity losses. The most common disturbance, by far, is a brief reduction in voltage, lasting for a few hundred milliseconds. These ‘voltage sags’ (in American English) or ‘voltage dips’ (in British English) are the most common power problem encountered in semiconductor Fabs around the world.

SEMI F47 Voltage Sag requirements

Some years ago, the solution to voltage sags was to use vast UPS or battery systems. But with more and more 300 mm Fabs in operation (and 450mm on the horizon) maintenance and regular replacement of such costly devices is a burden to every manufacturing facility. UPS and battery systems shall not be used in any tools (exception: FAB UPS for data systems).

Due to the extreme automation in new 300 mm semiconductor Fabs and only a few people inside the Fab, end-users want to have tools that are able to continue to run even after a voltage sag occurred. This continued operation is the Pass-Fail criteria outlined in SEMI F47-0200: “Equipment must continue to operate without interrupt during conditions identified in the area above the defined line”.

The SEMI F47 standard introduced a well thought out voltage-to-time curve that most semiconductor processing, metrology, and automated test equipment will be exposed to during normal operation.

SEMI F47 requires that tools tolerate the following voltage sags:

  • 50% remaining voltage, 50% missing voltage, for 200 milliseconds
  • 70% remaining voltage, 30% missing voltage, for 500 milliseconds
  • 80% remaining voltage, 20% missing voltage for one second.

In addition, SEMI F47 recommends, but does not require, that tools tolerate:

  • 0% remaining voltage, 100% missing voltage, for 1 cycle
  • 80% remaining voltage, 20% missing voltage, for 10 seconds.

Fig1 : The famous SEMI F47 ride-through curve

Who enforces SEMI F47?

Like any other SEMI standards, SEMI F47 is not a legal requirement, but required by most semiconductor manufacturers such as Intel, TI, IBM, Samsung etc. around the world. Every new semiconductor manufacturing tool that enters a SEMI Fab has to comply with the SEMI F47 Voltage Sag requirements. It is used both for semiconductor equipment, and for components and subsystems within semiconductor equipment. Enforcement is entirely customer-driven; the procurement agents of semiconductor equipment know the economic consequences of sag-induced failures, and generally refuse to pay for new equipment that fails the SEMI F47 immunity requirement. More and more tool manufacturers require the same from their component suppliers (power supplies, vacuum pumps, HF generators etc.). SEMI F47 Testing and Certification is usually an essential part of any tool purchase specification.

What are common responses to voltage sags, and how to address these problems?

  • Emergency Off (EMO) circuitry
  • Instrument and controller power supplies
  • Motion control drives
  • Voltage monitoring relays
  • Circuit breakers open due to increased current on phases without dip
  • Sensor faults or errors
  • Robot failure
  • Internal communication errors
  • Computer re-boots
  • Graceful restoration using power quality sensors

There are many low-cost solutions to these problems. Powering EMO circuits from 24 VDC instead of 24 VAC, de-rating power supplies or choosing SEMI F47 certified power supplies, inserting time delays or just a small software changes might help to solve a problem. Yet another common equipment failure mechanism involves some obscure sequence of events. For example, a voltage sag is applied to the equipment, and its main contactor opens with a bang. But further investigation reveals that a small relay connected in series with the main contactor coil actually opened, because it received an open relay contact from a stray water sensor. That sensor, in turn, opened because its small 24 VDC. supply output dropped to 18V during the voltage sag. (In this case, the solution is an inexpensive bulk capacitor across the 24 VDC supply.)

SEMI F47 was updated in 2006 and the latest version is officially called SEMI F47-0706. It will be harmonized with IEC 61000-4-34 which is the respective international Voltage Sag Immunity standard.

With the ever-increasing use of sophisticated controls and equipment in industrial, commercial, institutional, and governmental facilities, the continuity, reliability, and quality of electrical service has become extremely crucial to many power users. The power hardly gets better in the future, so the ultimate goal for any product manufacturer is to make its product immune to voltage sags.

Power Standards Lab
980 Atlantic Ave.
Alameda, California 94501
TEL: ++1.510.522.4400
US: 1.888.SEMI.F47 or 1.888.736.4347

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