---
title: "Cleanroom Thermoformed Trays: Cleanliness Specs | FUNYO"
description: "Specify cleanroom thermoformed tray surfaces separately from room air. Review a 20 m wash line, inspection methods and a CSV specification template."
type: landing
---

# Cleanroom Thermoformed Trays: Specify Air, Surfaces and Packing

A cleanroom class describes airborne particles: Class 100 is approximately ISO 5 at ≥0.5 μm, not a tray-surface cleanliness grade. Specify air class, surface acceptance and packaging separately.

## Specify room air and tray surfaces as separate requirements

A cleanroom tray specification needs separate requirements for room air, the product-contact surface and the delivered package. Airborne particles can settle on a tray, while trimming, handling and unpacking can add contamination later. The purchasing decision is therefore about the condition reaching the point of use and the evidence used to accept that condition.

ISO 14644-1 classifies air cleanliness by airborne particle concentration in cleanrooms and clean zones.[1](#source-1) A room report should identify the particle size, operating state and sampling locations. A surface inspection needs its own defined area and method. Keeping those records separate helps the buyer ask the supplier for evidence that addresses the actual risk.

A university's public table gives an ISO 5 limit of 3,520 particles/m³ at ≥0.5 μm.[2](#source-2) A government engineering guide identifies FED-STD-209E Class 100 as 100 particles/ft³ at ≥0.5 μm and compares it with ISO 5 at that size.[3](#source-3) Converting volume gives 100 × 35.31 ≈ 3,531 particles/m³, close to 3,520. This is an approximate comparison at the stated particle size; the specification should name the ISO class, particle size and test conditions directly.

The same university also approximately matches Class 10,000 with ISO 7; specify the particle size and measurement conditions when using that comparison.[2](#source-2)

方宇（FUNYO） has a 50 m² Class 100 room containing the wash line and a 1,500 m² Class 10,000 thin-gauge workshop, built in 2016. A laser particle counter monitors the Class 100 room's air. Agree tray-surface acceptance separately, identifying the contact zones, sampling method and relevant particle or residue limits.

![Illustration: Define air and surface sampling separately](/assets/guides/cleanroom-tray-cleanliness-specification/air-vs-surface-en.svg)

**Illustration** — Accept room air and tray surfaces separately; illustration

![Class 100 clean room, DI-water wash area](/assets/quality/cleanroom-class100.webp)

Class 100 clean room, DI-water wash area

## Trace contamination through sheet, cutting and handling

Follow the tray's route before deciding where cleaning belongs. Stored sheet can carry dust; trimming and die cutting can leave debris; nesting and handling create contact between surfaces. Looking only at the washer exit can miss what happens during bagging, opening or temporary storage beside the assembly line.

Mark cavity floors, sidewalls, locating edges and stacking contacts on the drawing. Identify the areas touching a sensitive product surface separately from handholds and external packaging contacts. An observed fibre or chip can then be associated with a particular zone and operation, rather than being recorded under a general description of a dirty tray.

For an incoming-contamination investigation, retain unopened, newly opened and used samples. Record the opening environment and sequence, and compare the packaging materials from the same shipment. Shape, colour and distribution help distinguish fibres, plastic fragments and films. The corrective action can then target the relevant handling step, contact material or wash condition.

FUNYO has produced thin-gauge trays since 2013 and has promoted permanent-ESD thermoformed boxes since 2014. Cleanliness and electrostatic protection belong in separate specification lines: one concerns residue, the other charge control. Packaging selection should address both shedding during opening and the electrical conditions at the intended workstation.

## Use the eight-step wash flow to define handovers

FUNYO's DI-water wash line is 20 m long with a 950 mm effective cleaning width, combining washing, air-knife drying and heated drying. Review access to surfaces, places that retain liquid and the handover into packaging. The delivery requirement should cover the complete sequence rather than only the spray stage.

1. **Load the washer.** Present trays in a supported orientation and identify areas hidden by contact or nesting. ![① Trays enter the washer](/assets/quality/wash-line-loading.webp)

① Trays enter the washer
2. **DI-water spray.** Identify deep pockets, cut edges and corners where the spray must reach or debris may remain. ![② DI-water spray wash](/assets/quality/wash-line-di-spray.webp)

② DI-water spray wash
3. **Heated drying and exit.** Examine retained water around recesses and contacts; set conditions for the material and shape. ![③ Heated drying and exit](/assets/quality/wash-line-dry-exit.webp)

③ Heated drying and exit
4. **Air-knife drying.** Check the exposed areas and protect cleaned surfaces during the next handover. ![④ Air-knife drying](/assets/quality/wash-line-air-knife.webp)

④ Air-knife drying
5. **Full visual inspection.** Associate visible anomalies with cavities, contact faces and the handling direction. ![⑤ 100% visual inspection](/assets/quality/wash-line-visual-check.webp)

⑤ 100% visual inspection
6. **Magnified sample inspection.** Observe agreed sampling positions and record particle appearance for source tracing. ![⑥ Magnified sample inspection](/assets/quality/wash-line-magnified-sampling.webp)

⑥ Magnified sample inspection
7. **Vacuum packing.** Seal inspected trays in the agreed package and assign responsibility for opening and repacking.
8. **Pass-box transfer to storage.** Keep the clean-area handover, package condition and batch identity traceable. ![⑧ Out through the pass box to storage](/assets/quality/wash-line-pass-box.webp)

⑧ Out through the pass box to storage

During sample review, consider pocket orientation, water retention, stacking supports and the way the tray travels through the line. Observe cleaned and dried samples before freezing the handling arrangement.

FUNYO inspects washed trays at 20× magnification and investigates the contamination source whenever a loose particle is found. That observation supports visible foreign-matter control. A buyer concerned with a particular particle size, chemical residue or transfer mechanism should specify the corresponding surface test and acceptance rule.

## Choose acceptance methods from the component's failure risk

Start with the effect a contaminant could have on the carried component. Particles may obstruct contact or assembly; ionic residue may matter to an electrical process; volatile material may matter where deposition on a sensitive surface is a concern. Define the object and endpoint before selecting an analytical method.

ISO 16232 addresses methods and records for particulate contamination on functionally relevant road-vehicle components and systems.[4](#source-4) Its scope can inform how the parties organize a cleanliness inspection. For an electronics tray, identify the agreed method and product-specific limit in the contract, matching them to the tray's intended use.

IEST-STD-CC1246 provides methods for specifying and determining cleanliness levels for contamination-critical products.[5](#source-5) Where the product team uses that framework, identify the selected requirement and inspection coverage in the order. A standard name still needs a defined contact surface, sampling procedure and acceptance criterion for the particular product.

| Concern | General method approach | Conditions to specify |
| --- | --- | --- |
| Surface particles | Agreed surface sampling or extraction followed by counting | Size bands, sampled area, background blank and reporting unit |
| Visible foreign matter | Visual and magnified observation | Lighting, inspected zones, magnification and anomaly records |
| Ionic residue | Extraction and analysis selected for the sensitive process | Target species, extraction medium, analytical method and units |
| Volatile material | Analysis selected for actual contact and storage conditions | Test conditions, target compounds, contact duration and decision rule |

State whether a sample was unopened, newly opened or already used. Those conditions represent different contamination routes even when the tray drawing is identical. Retained samples and blanks should stay linked to the batch, operator and sampling environment so the parties can reproduce an investigation.

## Preserve the washed condition through packing and opening

Protection after cleaning includes sealing, transfer, storage, transport and opening beside the production equipment. Review the packaging surface touching the tray, the closure method and the orientation in the package. Use physical samples to examine contact marks, abrasion and the way the trays settle under the planned handling arrangement.

FUNYO's recorded flow includes vacuum packing and pass-box transfer to storage. A buyer can add order-specific requirements for packaging units, label positions, opening location and return handling. If the receiving site divides a shipment into smaller quantities, include that repacking environment and its tools in the contamination route.

For reusable trays, record use condition and cleaning history. Inspect worn pocket walls, cut edges and stacking supports when investigating debris. Separating incoming issues from line-side handling and repeated-use effects helps each party identify an action it can control, rather than repeatedly changing the incoming acceptance threshold.

A useful packaging approval also shows what an operator does immediately before loading the component. Identify where the bag is cut, where its outer face is placed and which tray faces are touched. Keep this instruction beside the approved package sample so the receiving team can reproduce the protected state established during qualification.

## Turn cleanliness requirements into executable specification lines

A practical specification assigns the sample, method, decision and responsibility. The template below helps organize contract language; its examples describe what to agree rather than supply numerical acceptance values. Attach marked drawing zones and point-of-use information so the supplier can identify the surfaces and operations covered by each line.

| Clause | Suggested wording | Example | Who tests | Sampling |
| --- | --- | --- | --- | --- |
| Room air | State class, particle size, operating state and report coverage | Use the mutually agreed environmental conditions | Supplier monitors; buyer reviews | Agreed room sampling plan |
| Contact-surface particles | Mark zones, size bands and particle-count units | Use mutually agreed particle sizes and counts | Agreed testing party | By batch and designated contact zones |
| Visible foreign matter | Define faces, lighting, magnification and records | Use the approved anomaly decision rules | Supplier checks; buyer samples | Specified cavities and sampling plan |
| Chemical residue | Define species, method, units and background blank | Select targets from product sensitivity | Agreed laboratory | Agreed extraction and retained-sample plan |
| Washing and drying | Define process coverage and handover conditions | Use the approved sample process description | Supplier records; buyer reviews | Process and project inspection plan |
| Packing and opening | Define contact materials, sealing, opening and repacking owners | Use the approved packaging condition | Parties check their assigned handovers | Inspect seals by received batch |
| Dispute investigation | Define retained samples, background checks and responsibilities | Use the mutually agreed investigation flow | Jointly appointed parties | Review affected batch and retained samples |

Download the [cleanliness specification template](/downloads/guides/cleanroom-tray-cleanliness-specification/cleanliness-spec-template-en.csv) and complete the project conditions. Early samples can establish the method and background; supply inspection can then use the approved sampling and acceptance plan. Keep the signed specification tied to one tray revision and one delivered packaging condition.

Before approval, ask the receiving laboratory to describe how its result will be compared with the supplier's. Differences in extraction, sampled area or opening state can change the meaning of a number. Resolve those definitions while samples are available, and identify which retained material and records will support a later disagreement.

## When can an ordinary handling tray omit washing?

Ordinary circulation trays carrying non-sensitive components may be assessed using protected handling and routine inspection, especially where the next operation provides suitable treatment. Extra washing adds transfer, drying and packaging work. Select it when those operations address the actual product risk and remain compatible with the material and handling route.

Consider contamination tolerance, reuse, opening conditions and the consequence of an anomaly together. Sensitive optical surfaces, precision electronic contacts or residues that are difficult to remove downstream warrant a more explicit requirement. For ordinary structural parts, samples and representative handling can establish whether the proposed protection is appropriate.

The decision can be made during package qualification rather than after an incoming rejection. Compare the part's contact surfaces before and after representative handling, record any transfer and agree the protection needed. This keeps the cleaning scope connected to a visible acceptance decision and makes later changes easier to evaluate.

## Send the point of use and acceptance method with the inquiry

Mark the tray-to-product contacts, describe whether receiving feeds a sensitive station directly and complete the template. Put dimensions and cleanliness in separate drawing and inspection requirements; describe packaging as the delivered condition. Ask the supplier to return its testing and packing responsibilities before sample approval.

Review the [technical cleanliness process](/en/quality/technical-cleanliness), [thin-gauge thermoforming capability](/en/capabilities/thin-gauge-thermoforming) and [trays and liners](/en/products/trays-liners) for the available process context. The [electronics and advanced-equipment application](/en/industries/electronics-advanced-equipment) helps frame use conditions. For the forming route, read [thin-gauge versus heavy-gauge thermoforming](/en/guides/thin-gauge-vs-heavy-gauge-thermoforming) and keep the cleaning decision tied to the particular tray.

## Frequently asked questions

### Does production in a Class 100 room make a tray clean?

Not necessarily. Room classification concerns air, while cutting, handling and packaging can affect the tray surface. Define the product-contact zones, sampling method and limits separately, then accept the trays against the corresponding surface-inspection record.

### Do thermoformed trays need washing?

It depends on component sensitivity. Evaluate washing and protection for direct contact with optical surfaces, precision electronic areas or difficult-to-remove residues. For ordinary circulation, consider downstream treatment and use representative samples to choose the handling process.

### How should particles on a tray surface be checked?

Define contact zones and particle sizes before choosing sampling and counting. Record the background and reporting unit. FUNYO checks washed trays at 20× magnification for foreign matter; agree separate methods for other surface acceptance characteristics.

### How should washed trays be packed?

Specify packaging contact surfaces, closure and opening together. FUNYO’s recorded flow includes vacuum packing and pass-box transfer to storage. The order should also assign packaging units, storage conditions and responsibility for any subdivision after the shipment is received.

### Which ISO class approximately corresponds to Class 100?

At ≥0.5 μm, Class 100 is commonly compared approximately with ISO 5. Specify the ISO 14644-1 class, particle size and operating state directly, and check that the supplier’s report covers the agreed sampling and test conditions.

## Sources

### 1. [ISO 14644-1:2015 — Abstract](https://www.iso.org/standard/53394.html) [#source-1]

ISO · 2026-10-29

### 2. [Cleanroom — ISO 14644-1 and FED STD 209E tables](https://cense.engr.uky.edu/equipment/cleanroom) [#source-2]

University of Kentucky, Center for Nanoscale Science & Engineering · 2026-10-29

### 3. [Contamination Engineering Design Guidelines](https://epact2.gsfc.nasa.gov/tycho/STEREOContamControl.htm) [#source-3]

NASA Goddard Space Flight Center · 2026-10-29

### 4. [ISO 16232:2018 — Abstract](https://www.iso.org/standard/70267.html) [#source-4]

ISO · 2026-10-29

### 5. [IEST-STD-CC1246E: Product Cleanliness Levels](https://www.iest.org/Standards-RPs/Recommended-Practices/IEST-STD-CC1246) [#source-5]

IEST · 2026-10-29

## Related reading

[All articles](/en/guides)

- [Thin-Gauge vs Heavy-Gauge Thermoforming for Parts](/en/guides/thin-gauge-vs-heavy-gauge-thermoforming)

- [Cleanliness specification template](/downloads/guides/cleanroom-tray-cleanliness-specification/cleanliness-spec-template-en.csv) — Matches the webpage table; complete the project conditions.