How do you calculate a particle control risk score?

Multiply the severity, occurrence, and detection scores together. With ratings of 6, 4, and 3 on this tool's scale the result is about 4.55, so keep the same scale across every risk you compare.

What is a good particle control risk score?

Lower is better; there is no universal cutoff, so set a threshold for your program and act on anything above it. Rank risks relative to each other rather than chasing an absolute number.

What do severity, occurrence, and detection mean here?

Severity is how bad the contamination is if it reaches the wafer, occurrence is how likely a particle excursion happens, and detection is how hard it is to catch before shipment. High detection scores mean the problem is hard to find, which raises risk.

Why is my score 4.55 and not 72?

This preset normalizes the multiplied result to its own scale rather than the raw 6x4x3=72. What matters is that you score every risk the same way so the numbers are comparable.

Should I always fix the highest score first?

Start there, but also review any high-severity item on its own even if its total is modest, because a rare but wafer-killing excursion can outrank a frequent nuisance. RPN is a prioritizer, not a substitute for judgment.

Particle control risk vs actual particle count, what is the difference?

Particle count is a measured cleanliness metric on a real tool; this risk score is a forward-looking prioritization of failure modes. Use counts to verify and the score to decide where to spend engineering effort.

Semiconductor Fab Equipment Manufacturing calculator

Particle Control Risk Calculator

Particle control risk is an FMEA-style priority score that ranks contamination hazards on fab equipment by multiplying severity, occurrence, and detection ratings. Cleanliness engineers, reliability teams, and quality leads use it to decide which particle sources on a tool or sub-assembly get engineering attention first, because not every risk is worth the same money. A high score flags a failure mode that is damaging, likely, and hard to catch before it ships. This calculator gives you a single comparable number so you can rank risks on the same scale instead of arguing from gut feel.

What this calculator does

Estimate particle control risk for semiconductor fab equipment manufacturing using production-ready inputs so teams can rank risks and decide which issue needs containment, controls, or escalation first.
Use it when particle control risk in semiconductor fab equipment manufacturing needs a defensible ranking against other semiconductor fab equipment manufacturing risks for the next review.
It computes a particle control risk priority number by multiplying severity, occurrence, and detection scores.

Formula used

Particle control risk score = particle control risk severity score × particle control risk occurrence score × particle control risk detection score
Use the same scoring scale across comparable particle control risk risks.

Inputs explained

Contamination severity if it reaches the wafer:
Likelihood of a particle excursion:
Detectability before shipment:

How to use the result

Use it during a contamination FMEA or design review to rank and prioritize particle-generation risks.
RPN treats the three factors as equal multipliers, so a very high-severity risk can be masked by low occurrence and detection scores and needs separate review.

Current U.S. benchmarks

The producer price index for copper and brass mill shapes stands at 559.593 (BLS, May 2026), up 76.8% from a year earlier. Quotes priced off last quarter's material cost miss this move. Global copper trades at $13,484 per tonne (IMF via FRED, May 2026).
Steel mill PPI stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. New factory orders are up 2.3% year over year (Census).
The U.S. has 11,261 computer and electronic products establishments employing about 815,443 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate a particle control risk score? Multiply the severity, occurrence, and detection scores together. With ratings of 6, 4, and 3 on this tool's scale the result is about 4.55, so keep the same scale across every risk you compare.
What is a good particle control risk score? Lower is better; there is no universal cutoff, so set a threshold for your program and act on anything above it. Rank risks relative to each other rather than chasing an absolute number.
What do severity, occurrence, and detection mean here? Severity is how bad the contamination is if it reaches the wafer, occurrence is how likely a particle excursion happens, and detection is how hard it is to catch before shipment. High detection scores mean the problem is hard to find, which raises risk.
Why is my score 4.55 and not 72? This preset normalizes the multiplied result to its own scale rather than the raw 6x4x3=72. What matters is that you score every risk the same way so the numbers are comparable.
Should I always fix the highest score first? Start there, but also review any high-severity item on its own even if its total is modest, because a rare but wafer-killing excursion can outrank a frequent nuisance. RPN is a prioritizer, not a substitute for judgment.

Last reviewed 2026-05-12.