A PCB cleanliness result is useful only when the team has defined the product risk, test method, sample state, extraction or coupon conditions, acceptance basis, and release owner. ROSE can monitor bulk extractable ionizable residue, ion chromatography can identify and quantify extracted ionic species, and SIR can characterize a material or process under controlled humidity and electrical bias. None of these tests, by itself, proves product life or final system qualification.
Use this guide to make three connected decisions:
- Designer or engineer: identify contamination-sensitive areas and decide whether a bulk sample, localized investigation, or controlled test vehicle represents the risk.
- Quality or NPI: specify the method, revision, sample plan, controls, result format, acceptance basis, traceability, retest, and release authority.
- Procurement: compare quotations using the same test scope and deliverables instead of treating
IPC compliantor a single cleanliness number as a complete requirement.
What does PCB cleanliness testing actually prove?
Cleanliness testing provides evidence about the sample, method, conditions, and residues that the selected procedure can detect. Its meaning changes when any of those inputs changes.
A bulk extraction from a complete assembly may support process monitoring, but it may not represent residue trapped under a low-standoff component. A chromatogram can identify extracted ions, but it does not automatically locate where they came from. A coupon SIR result can compare a material or process under controlled conditions, but it is not the same as validating every production geometry or end-use environment.
Before selecting a method, state the decision the result must support:
- Is the team monitoring a stable fabrication or assembly process?
- Is it identifying ions during a residue or failure investigation?
- Is it qualifying a flux, material, cleaning process, or process change?
- Is it releasing a production lot against a customer-defined requirement?
- Is it validating the complete product for its electrical, environmental, safety, or regulatory use?
The fifth decision requires a product-specific qualification plan. It cannot be replaced by a single cleanliness test.
Which cleanliness method fits the decision?
Use the following matrix before putting a method name into a drawing, control plan, purchase order, or RFQ.
| Risk or decision | Evidence route | Representative sample | Useful output | Important limitation | Release owner |
|---|---|---|---|---|---|
| Monitor bulk extractable ionizable residue | ROSE under a defined IPC-TM-650 2.3.25 method and process-control plan | Defined bare-board or PCBA area in a known process state | Raw reading and surface-normalized ug NaCl equivalent/cm2, tied to method and conditions |
Does not identify ionic species, detect every localized or non-ionic residue, or predict reliability | Customer/project team defines the contractual level; manufacturer provides the quoted process evidence |
| Identify and quantify extracted ionic species | Ion chromatography under IPC-TM-650 2.3.28 for boards/assemblies or 2.3.28.2 for bare boards | Traceable board, assembly, coupon, or targeted sample compatible with the extraction plan | Blank-corrected ion results, normalized results, and chromatogram when required | Does not automatically locate the residue, identify every possible contaminant, or set a universal pass/fail limit | Qualified laboratory owns analytical validity; project team defines ions, limits, and disposition |
| Compare flux, material, or assembly-process behavior under humidity and bias | SIR with the applicable standard vehicle, controls, bias, humidity, duration, and governing specification | Standardized coupon or other explicitly approved test vehicle | Resistance data, trend, electrochemical observations, deviations, and control results | Does not automatically qualify a shipped assembly, end-use environment, or product lifetime | Project team owns qualification; laboratory owns valid execution; manufacturer owns the represented process |
| Investigate suspected localized residue | Location-preserving inspection and targeted extraction followed by IC or another validated analytical method | Marked affected and control locations with chain of custody | Location map, photographs, raw analytical data, controls, and disposition | A whole-board bulk extraction loses location information; an image alone does not quantify ionic loading | Joint investigation with project-team release authority |
| Validate product or system reliability | Product-specific electrical, environmental, mechanical, functional, and regulatory plan | Released product configuration with justified sample size | Results against named product requirements and acceptance criteria | ROSE, IC, or coupon SIR alone cannot close this decision | Customer or product authority |
The method name is only the beginning. Sample identity, test conditions, controls, units, acceptance source, and responsibility determine whether two results are comparable.
When should ROSE be used?
ROSE, or resistivity of solvent extract, is a bulk process-control method. IPC-TM-650 2.3.25D covers printed boards and assemblies and reports a conductivity-equivalent result normalized to area. The result is expressed as NaCl equivalent; it does not mean the residue has been chemically identified as sodium chloride.
ROSE is useful when the team wants to monitor a defined process against a customer-approved control level. It is less useful when the decision requires ion identification, precise residue location, non-ionic contamination analysis, or direct product-reliability evidence.
A reviewable ROSE record should identify at least:
- the exact method and revision;
- bare board or assembly condition, revision, lot, and tested area;
- solvent composition, volume or flow, time, and temperature;
- equipment or tester model and calibration identity;
- area calculation and raw and normalized results;
- control, blank, baseline, or correlation practice required by the governing plan;
- the customer-defined control or acceptance level; and
- deviations, retest rule, nonconformance disposition, and release authority.
Do not compare two ROSE numbers until tester style, extraction conditions, area calculation, and process state are compatible.
When is ion chromatography the better choice?
Ion chromatography is the stronger route when the decision requires identification and quantification of extracted ionic species. IPC-TM-650 2.3.28B applies to printed boards and assemblies, while IPC-TM-650 2.3.28.2 addresses bare printed boards. The sample and extraction procedure must match the selected method.
An IC request should define:
- the sample state, quantity, revision, lot, and area calculation;
- the extraction solution, volume per area, time, temperature, and handling;
- an empty-bag blank or other applicable control processed with the sample;
- the ions or weak organic acids to be reported;
- instrument and calibration traceability;
- blank-corrected concentration and surface-normalized result;
- chromatogram delivery, reporting threshold, and treatment of unidentified peaks;
- destructive-sample disposition and chain of custody; and
- retest, deviation, and release rules.
The standard high-temperature extraction used by some IC procedures may not be suitable for every populated assembly or component. Confirm sample compatibility and whether the production article will be consumed or altered before testing.
For a localized investigation, do not send an unmarked whole assembly and expect the chromatogram to identify the source location. Define affected and control regions, preserve handling history, and use a sampling approach that retains the location information needed by the investigation.
What does SIR add that extraction tests cannot?
Surface insulation resistance testing examines electrical behavior under controlled environmental and bias conditions. It can support material or process characterization when the test vehicle, preparation, controls, chamber conditions, electrical field, duration, measurements, observations, and acceptance basis are defined.
SIR is not one universal recipe. For example, IPC-TM-650 2.6.3.7 specifies a controlled method using standard test vehicles, 40 +/- 1 C, 90 +/- 3% RH, an electrical field of 25 +/- 1 V/mm, and at least 72 hours. Other SIR methods use different vehicles and conditions for different purposes. Do not substitute an 85 C / 85% RH flux test or another laboratory protocol and call it IPC-TM-650 2.6.3.7.
A useful SIR package should name:
- the test method, revision state, governing specification, and acceptance basis;
- coupon or vehicle design, controls, preparation, and process representation;
- flux, material, cleaning state, and conditioning history;
- chamber temperature and humidity, applied bias or field, and duration;
- measurement interval, raw resistance data, calculation, and excluded readings;
- dendrite, corrosion, discoloration, water-spot, or other required observations;
- deviations, failures, retest, and disposition; and
- the relationship between the test vehicle and the released production process.
Even a passing SIR result does not prove the lifetime, regulatory compliance, or environmental performance of the complete product.
Why do sample state and location change the answer?
The words PCB cleanliness can refer to several different evidence objects. They are not interchangeable.
| Sample state | Decision it can support | What must be recorded | Common interpretation error |
|---|---|---|---|
| Bare printed board | Fabrication-process monitoring or investigation before assembly | Finish, storage and handling state, lot/panel linkage, area, extraction or coupon method | Treating a bare-board result as proof of the later assembly process |
| Populated PCBA | Evidence for the assembled process and its residues under the selected extraction | Assembly revision, flux/paste, cleaning state, components, area, sample disposition | Assuming a bulk extraction represents every hidden location |
| Witness or process coupon | Controlled comparison or qualification of a material/process route | Coupon design, placement in process, controls, conditioning, lot linkage | Treating the coupon as identical to every product geometry |
| Targeted location | Residue investigation tied to a suspected feature or failure hypothesis | Location map, handling, extraction footprint, control location, photographs | Losing location information through whole-board extraction |
| Finished product or system | Product-specific qualification only when the complete plan says so | Released configuration, environment, sample size, functional limits, failures, approval | Claiming a cleanliness result alone qualifies the product |
Design teams should identify areas that a bulk extraction may under-represent, such as low-standoff packages, shielded or enclosed regions, connectors, coating boundaries, high-impedance nodes, and areas with restricted wash or rinse access. That list guides sampling and investigation; it does not prove contamination exists.
How should a quality team define the acceptance basis?
Do not use one historical number as a universal cleanliness limit. The often-repeated 1.56 ug/cm2 NaCl equivalent value does not, by itself, define acceptance for every bare board, PCBA, flux system, geometry, process, or end-use environment.
Instead, tie acceptance to a named source and project decision:
- a customer drawing, specification, or approved control plan;
- the applicable IPC method and revision;
- a qualified material or process baseline;
- a statistically justified process-monitoring limit;
- a product-specific qualification plan; or
- another contractually accepted requirement with clear ownership.
The record should distinguish a process-control alert from a product rejection. It should also state who can approve a deviation, when retest is allowed, what requires containment or NCR, and what process or material change triggers requalification.
PCB cleanliness release checklist
Use this checklist before a lot is released against a cleanliness requirement.
Requirement and sample
- Name the board or assembly, revision, process state, quantity, and lot/panel/unit linkage.
- State the risk or decision being tested, not only the method acronym.
- Identify the standard, method, revision, units, and customer acceptance source.
- Define the tested area, location, production article, witness coupon, or control vehicle.
- Record destructive-test restrictions, storage, packaging, handling, and chain of custody.
Method and controls
- Freeze extraction composition, volume or flow, time, temperature, area calculation, or SIR conditioning and bias.
- Define blanks, control bags, cleaned control coupons, baselines, and correlation rules as applicable.
- Require laboratory, equipment, method, and calibration identity appropriate to the contract.
- Record all deviations from the specified procedure before interpreting the result.
Results and disposition
- Request raw and normalized results with units and calculation basis.
- Request chromatograms, photographs, location maps, and electrochemical observations where applicable.
- Link the report to the sample, lot, method, revision, date, and responsible organization.
- Define pass, process alert, hold, containment, NCR, retest, and release authority.
- State record retention and change-notification requirements.
Responsibility boundary
- Manufacturer: supplies only the process, samples, controls, traceability, tests, and records agreed in the quotation and quality plan.
- Customer/project team: defines product risk, contractual acceptance, deviations, release authority, and final product or system qualification.
- Qualified laboratory: owns valid analytical or environmental execution, calibration, controls, data integrity, and stated deviations within its contracted scope.
What should procurement put in a cleanliness-testing RFQ?
Procurement should make competing quotations technically comparable. Submit the released fabrication and assembly data plus a cleanliness evidence schedule containing:
| RFQ field | What to provide | What the returned quotation should confirm |
|---|---|---|
| Decision and scope | Process monitoring, residue investigation, material/process qualification, lot release, or another named purpose | Whether the proposed route can answer that decision |
| Method | Standard, method number, revision, units, extraction or SIR conditions | Exact method offered, substitutions, and deviations |
| Sample plan | Bare board, PCBA, coupon, target location, quantity, frequency, and lot linkage | Accepted sample state, count, ownership, and destructive disposition |
| Acceptance | Customer limit, control plan, governing specification, and release authority | What constitutes pass, alert, hold, retest, and NCR |
| Report package | Raw/normalized data, blanks/controls, calibration identity, chromatogram, photos, observations, and traceability | Included and optional deliverables, format, timing, and responsible issuer |
| Records and changes | Retention period, deviation approval, and requalification/change-notification triggers | Contracted retention and notification boundary |
The current HILPCB quote form can receive these requirements through Special Requirements and uploaded files. HILPCB's formal PCB and assembly pages allow cleanliness checks or records to be discussed when required, but they do not establish a standard ROSE, ion-chromatography, or SIR service package. The returned quotation must confirm feasibility, execution party, sample plan, method, acceptance basis, and included records for the specific project.
Submit the evidence schedule with the board files through Request a Quote. Use the PCB Assembly or Turnkey Assembly scope only as project context; neither page replaces the method and report requirements above.
Frequently asked questions
Is ROSE the same as ion chromatography?
No. ROSE measures bulk extractable ionizable residue through conductivity and reports a NaCl-equivalent result normalized to area. Ion chromatography separates and quantifies extracted ionic species. Neither method automatically locates residue or proves product reliability.
Is 1.56 ug/cm2 a universal PCB cleanliness limit?
No. Do not apply one historical number to every bare board, assembly, flux system, geometry, process, and end use. Define the method, revision, sample, conditions, units, acceptance source, and project-specific release authority.
Does a passing ionic-cleanliness result prove a PCBA is reliable?
No. It provides evidence for the sample and method tested. Product reliability also depends on design, materials, manufacturing, environment, electrical stress, mechanical construction, and the complete qualification plan.
Should a production assembly be used for ion chromatography?
Only after the team confirms that the selected extraction is compatible with the populated components and accepts any destructive or altering effects. Define sample disposition, chain of custody, controls, and whether a coupon or dedicated sample would better answer the decision.
Can HILPCB provide ROSE, ion chromatography, or SIR reports?
The current formal pages do not establish a standard named-method service or report package. Put the exact method, sample, acceptance, execution, and report requirements in the RFQ, then require the returned quotation to identify what is feasible, included, optional, or external for that project.
Build a reviewable cleanliness evidence package
Start with the decision, then lock the method, sample, controls, result format, acceptance basis, traceability, and owner. This makes the evidence reviewable by engineering, quality, procurement, the manufacturer, and any qualified laboratory without turning a process-control number into a product-life claim.
Reference basis: IPC-TM-650 2.3.25D, Detection and Measurement of Ionizable Surface Contaminants by Resistivity of Solvent Extract (ROSE); IPC-TM-650 2.3.28B, Ionic Analysis of Circuit Boards, Ion Chromatography Method; IPC-TM-650 2.3.28.2, Bare Printed Board Cleanliness by Ion Chromatography; IPC-TM-650 2.6.3.7, Surface Insulation Resistance; IPC J-STD-001J, Requirements for Soldered Electrical and Electronic Assemblies (title and revision verified; paid cleanliness clauses not used here); and IPC-CH-65B, Guidelines for Cleaning of Printed Boards and Assemblies (public table-of-contents/scope boundary only).