RAYPCB · ENGINEERING GUIDE
IPC-5704: Bare PCB Cleanliness, Sampling and Test Interpretation
IPC-5704 addresses cleanliness requirements for unpopulated printed boards. Its scope matters: a bare-board cleanliness requirement is not automatically the same as a requirement for an assembled board with flux residues, components and additional process history.
The official revision table consulted for this guide lists IPC-5704 as no longer maintained, with the original issue dated December 2009. Confirm its contractual role and applicable requirements for the project.
This page helps engineers and buyers define a test and reporting scope. It does not supply a universal contamination limit or convert an arbitrary conductivity reading into a pass. The calculator normalizes an entered mass result by a declared area only when the measurement basis is already established.
Start with the contamination question
Identify what you need to learn: a broad process-monitoring result, a specific ionic species, localized residue or another characteristic. Different methods observe different aspects of cleanliness. A single result should not be presented as proof that every possible contaminant is absent.
State the board condition and process stage. A bare board before assembly, a board after handling and a completed PCBA have different histories. If the concern originated during assembly, route the investigation through the relevant assembly process rather than silently applying a bare-board requirement to a different sample.
Blank-adjusted mass per area
Blank-adjusted mass per area
Use the current inputs and keep the assumptions
Start with the feature or process question you actually need to resolve. Fields are blank until you enter values or deliberately load an illustrative example. Example mode remains labeled after editing, so a sample is not silently presented as verified project data. Clear the example before preparing a project-specific record.
Use the units printed beside each input. Keep the drawing revision, measurement basis and source of any allowance in your controlled project records. A field that asks for a limit expects your agreed requirement; the example is not an IPC threshold or a statement of RAYPCB capability. A numerical result should lead to a focused review, not replace it.
Changing any input invalidates the displayed result and disables its download until you calculate again. The text download contains the current inputs, results and assumptions. Nothing is uploaded, stored in analytics or automatically transferred into the Contact form. You may attach the file manually if it helps explain your enquiry; completing the worksheet is optional.
| Input | What to establish before using it |
|---|---|
| Review reference | Use a nonconfidential reference to connect this worksheet to the correct design or process revision. |
| Measured mass or agreed equivalent · micrograms | Use a method-defined mass basis; no conductivity-to-mass conversion is performed. |
| Blank on the same mass basis · micrograms | A larger blank produces a flagged negative result rather than a hidden zero clamp. |
| Procedure-defined sampled area · cm² | Use the method area convention; do not automatically double the outline area. |
Select a method that answers the question
Extraction-based measurements, species-specific analysis and localized examination have different strengths and limits. The applicable specification and agreed procedure should identify the method, extraction conditions, sample preparation and reporting basis. Public contents and scope information cannot substitute for those controlled details.
Do not assume that two results are comparable merely because both are labeled ionic contamination. Differences in extraction, calibration, units or area definition can change their meaning. When comparing suppliers or historical records, first reconcile the method and sample conditions.
| Review item | What to establish |
|---|---|
| Scope | Identify unpopulated board condition and the stage at which it is sampled. |
| Method | Retain extraction, calibration, analyte or equivalent basis and units. |
| Area | Use the denominator defined by the selected procedure. |
| Decision | Keep normalization, acceptance requirement and disposition separately documented. |
Define the sampled area and blank
Area-normalized results need a stated area convention. Clarify whether the calculation uses one side, both sides or another procedure-defined area. Do not casually double a board's outline area when the selected method defines the denominator differently.
The blank helps characterize contribution from the measurement system or procedure under the applicable method. The worksheet subtracts an entered blank mass from an entered measured mass, then divides by the declared area. It assumes both mass values share the same analyte or equivalent basis. It does not derive mass from conductivity.
Interpret negative blank-adjusted results honestly
If the blank exceeds the measured value, the arithmetic result is negative. That does not mean the board contains negative contamination. It indicates a condition that must be interpreted using the method's uncertainty, detection and reporting rules.
The tool retains the signed result and flags it for review instead of silently clipping it to zero. This prevents a data-processing choice from becoming a false claim of perfect cleanliness. Record the original values and the method's handling of such results in the report.
Keep sampling representative
Identify the lot, board revision, manufacturing stage and sample selection method. A conveniently available board may not represent the most relevant process condition. If a localized issue is suspected, an overall extraction can obscure where the residue is concentrated.
Retain sample identity and relevant handling history. Packaging, gloves, fixtures and storage can affect the condition observed at test time. The control plan should connect the test to a process question, such as a change in cleaning or a suspected handling source, rather than collecting numbers without an action rule.
Agree limits and disposition before testing
Use the applicable controlled requirement and customer agreement to define acceptance. Specify how uncertainty, repeated tests and atypical results will be handled. Avoid selecting a convenient limit after seeing the result or borrowing a number from a different product and method.
The tool does not contain a pass threshold. That is intentional: a numerical normalization is not a universal IPC compliance test. Keep the requirement, observation and disposition as separate fields in the quality record so a later reviewer can reconstruct the decision.
Request a useful cleanliness report
Ask for sample identification, method and revision, extraction or preparation basis, units, blank treatment, area definition and individual results. Include the acceptance criterion and any uncertainty or reporting information required by the method. A certificate containing only the word clean is not equivalent to this evidence.
For review with RAYPCB, provide the bare-board construction, intended assembly route and specific cleanliness concern. If the sample is already populated, say so at the start. This helps route the request to the right investigation and prevents an attractive but irrelevant test result from delaying the real corrective action.
Preserve enough context to compare two cleanliness results
Begin with sample identity and condition. State whether the board is unpopulated, which manufacturing stage it represents and how it was handled before analysis. An unexplained difference in sample history can be more important than the difference between two reported numbers.
Next, compare methods and reporting bases. The extraction conditions, analyte or equivalent definition, calibration, units and area convention should be compatible before values are combined or trended. A broad test label does not establish that compatibility. Retain the original method record so a later reviewer can reconstruct the normalization.
Keep blanks and unusual results visible. A blank-adjusted value below zero needs interpretation under the method's uncertainty and reporting rules; it should not become a marketing claim of zero contamination. Likewise, a low overall result does not necessarily exclude a localized residue at a critical feature.
Use sampling to answer a defined process question. If the concern is a handling step, compare samples that isolate that step where practical. If the concern is a material or cleaning change, preserve an appropriate baseline. Do not infer a lot-wide result from an undocumented convenience sample.
The purchase requirement should state the needed evidence and acceptance basis. Additional analysis can be valuable, but only when it addresses the product's uncertainty. A clear report with method, sample, units and decision basis builds more trust than a large number of unrelated tests or an unsupported statement that the board is chemically clean in every possible sense.
Standards, source context and limits
Use the official references for their stated scope and the applicable controlled document for contractual requirements. A public scope page, product description or application note is not a complete acceptance specification. Material-supplier guidance applies to the named material and process; it is not evidence that every option is available for this board.
Agree the document revision, construction, inspection method and any exceptions with the responsible engineering and quality teams. The explanatory drawings and worksheet examples on this page are original planning aids, not factory records, qualification results or compliance certificates.
