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Knowledge Base/Standard Procedures for Equipment Acceptance Testing (FAT/SAT)
Equipment Engineering6 min read

Standard Procedures for Equipment Acceptance Testing (FAT/SAT)

This article addresses common issues leading to poor equipment performance and low yield, often stemming from inadequate or skipped Factory Acceptance Tests (FAT) and Site Acceptance Tests (SAT). It underscores the critical importance of robust FAT/SAT procedures to ensure new machinery meets specifications and operates reliably, preventing costly production issues.

That Day, the PM Said to Me: "Senior, Why Is the Yield of This Machine So Terrible?"

That day, I was sitting in my office, about to enjoy my coffee before lunch break. Suddenly, PM Xiao Hua rushed in, his face ashen. "Senior, why is the yield of this new machine so terrible? Our production line is getting hammered!" He slammed a yield report onto my desk. I glanced at it; the Cpk value was only 0.85, and DPMO was as high as 12,000. The new machine had just been installed, and theoretically, it should be in its prime condition, so how could this be? I thought to myself, it's highly probable that the FAT/SAT wasn't done properly, and subsequent problems were snowballing.

Where Does the Problem Lie? The Equipment Was Deployed Without Being Properly Prepared!

In essence, FAT (Factory Acceptance Test) and SAT (Site Acceptance Test) are about ensuring your new equipment is "battle-ready" before it officially goes online for production. Imagine you buy a brand new electric car; wouldn't you first take it for a test drive at the showroom to confirm all functions are normal? Then, after driving it home, would you test the automatic parking and charging functions in your own parking lot? This is precisely what FAT and SAT entail.

The key point is that FAT is the acceptance test conducted at the equipment supplier's factory to confirm the machine's basic functions and specifications; SAT, on the other hand, is performed at our own factory premises to ensure the machine seamlessly integrates with our production environment. Many times, to save time, FAT/SAT are rushed through, leading to situations like what Xiao Hua encountered, where new equipment becomes a cancer on the production line.

How to Actually Do It to Avoid Pitfalls?

Frankly speaking, the standard procedure for FAT/SAT is essentially a detailed "acceptance checklist." We typically require the supplier to provide this checklist, and it's finalized during contract signing.

  1. Specification Confirmation: This is the most basic, yet also the most easily overlooked step. It's not just about checking if the model number is correct; it requires cross-referencing every critical dimension, weight, interface, power consumption, and so on, for the machine. All specifications stated in the contract must match. I once encountered a situation where the machine's dimensions were off by 5 centimeters, resulting in it being unable to enter the cleanroom door, getting stuck for several days, causing significant losses.

  1. Functionality Test: This is the main event. We will prepare a detailed test plan covering the operational status of each major function of the machine. For example, the speed and accuracy of automatic wafer transfer, the pumping speed and stability of the vacuum pump, the stability of temperature control, and so on. We will require the supplier to perform these tests on-site and record the data.

  1. Performance Verification: This is crucial for determining if the machine can be profitable. We will use actual or simulated wafers to run a small batch production and then analyze the results. For instance, we will require that under specific processes, the machine's Cpk value must reach 1.33 or higher (indicating sufficient process capability), or DPMO (Defects Per Million Opportunities) must not exceed 3.4 (number of defects per million operations). If the data provided by the supplier shows a Cpk of only 1.08 and DPMO as high as 6210, then this machine absolutely cannot be released!

  1. Safety Inspection: This point is extremely important! The machine's emergency stop buttons, safety door interlocks, hazardous area warning lights, and so on, must all be checked one by one, and their effectiveness must be physically tested. After all, no matter how profitable a machine is, it cannot outweigh the importance of employee safety.

In other words, you must act like a detective, thoroughly examining the machine from top to bottom, inside and out, to ensure it is truly a "good" machine.

The Most Common Pitfalls: Personal Favor Pressure and Rushing Deployment

The most common pitfalls I've encountered are "rushing for time" and "pressure for personal favors." Sometimes the production line is urgent, and PMs are being watched by the boss, so they think of relaxing FAT/SAT a bit, just letting the machine in first. What's the result? After the machine is installed, problems are constant; either the yield is poor, or it crashes every other day. The supplier's personnel have also left, and asking them to come back to deal with it is time-consuming and wasteful.

Another time, the supplier's sales representative told me: "Engineer, we've cooperated for so long, it's just a small issue, please do me a favor and approve it." As a result, I softened and signed off. In less than a month, that machine caused millions in scrap. That lesson taught me that in professional work, when it's time to adhere to principles, you absolutely cannot compromise. Because all the subsequent messes will be yours, the engineer, to clean up.

One Thing You Can Do Today

Next time you accept a machine, make sure to insist on "black and white, supported by data."

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