Copper Oxide Particle Size for PCB Plating: Reading D10, D50 and D90

Copper Oxide Particle Size for PCB Plating: Reading D10, D50 and D90

Publication date: 2026-10-20 | Category: PCB Plating Procurement Guide | Reading time: Approximately 11 minutes

A copper oxide specification may list an “average particle size” without saying how that average was calculated. A test report may then show D50, D90 and a volume mean diameter, each with a different value. Before those results can support a purchasing decision, the buyer needs to establish what each number represents and whether the test conditions are comparable.

One Zhongan Copper sample report lists a D50 of 26.57 μm and a D90 of 39.35 μm. View the particle size report to open the original image, which can also be saved. The report identifies its results as a volume distribution.

That detail governs how the numbers should be read. For a PCB plating material review, the practical questions are what was measured, how the result was obtained, and whether it can be used to compare the samples under consideration.

D10, D50 and D90 depend on the distribution basis

In a volume distribution, D10, D50 and D90 are the diameters below which approximately 10%, 50% and 90% of the reported particle volume falls. They are also written as Dv10, Dv50 and Dv90, with “v” identifying the volume basis.

Volume and particle count are different bases. A volume-based D50 of 26.57 μm does not mean that half the individual particles, counted by number, are smaller than 26.57 μm.

Check the basis whenever a report uses D50 without further explanation. Malvern Panalytical’s guide to particle size distributions distinguishes volume, number and other weightings. Keep that information alongside the numerical result when comparing reports.

D90 is a percentile rather than a cutoff. Larger particles may still be present. It should therefore not be substituted for a maximum-size limit or a requirement for complete passage through a stated sieve.

Reading the median, mean and mode in an actual report

The Zhongan Copper report used here is dated 10 July 2026. It identifies Zhongan Copper as the testing organization and the copper oxide production workshop as the sample source. Its principal statistics include:

D50, D[4,3] and the modal diameter have different definitions. Their values need not coincide. In this example, 26.57 μm, 25.96 μm and 29.44 μm describe different statistics from the same report; the differences alone do not establish an error. HORIBA’s explanation of particle size calculations covers the distinction between median, mean and mode.

The detailed table provides a useful cross-check. Cumulative volume reaches 49.00% at the 26.33 μm boundary and 62.22% at 29.62 μm. The 50% point lies between them, consistent with the reported D50 of 26.57 μm. This checks where the median falls; it does not reproduce the software’s interpolation from the displayed interval boundaries.

Retain the full curve and interval table when reviewing a report. They preserve information that a single “average size” entry leaves out and make later checks easier.

These values describe the sample in this report. They are not guaranteed values for every delivered lot or proposed acceptance limits for a customer’s process.

A practical sequence for reviewing the report

Use the following sequence for an initial review, retaining enough information to trace each result to its sample.

1. Establish sample identity. Record the sample name, source and test date, and match them to the submission records. In this example, the date is the test date. The word translated as “average” in the sample name does not establish how many measurements or lots were included.

2. Check the distribution basis and units. This report identifies a volume distribution and gives sizes in μm. Interpret its percentiles on that basis. If the customer specification uses another weighting, resolve the difference in definitions before comparing values.

3. Record the median and mean separately. D50 is 26.57 μm, while D[4,3] is 25.96 μm. Preserve those parameter names in the purchasing record rather than placing either result in an undefined “average size” field.

4. Read the curve together with the interval table. The red curve in the original report shows the interval distribution; the table also provides cumulative percentages. Use the cumulative data to locate the 50th percentile, rather than looking for 50% on the red curve’s vertical axis. Retain the full curve for laboratory review of the distribution’s fine end, coarse end and other details.

5. List the information still needed. The results page alone does not establish the complete method, sampling procedure or repeatability. Request the missing records so that laboratory or quality staff can determine whether further information or repeat testing is necessary.

The outcome should be a traceable review entry identifying the sample, date, distribution basis, reported statistics and outstanding method questions. That record is more useful for subsequent checks than an isolated entry reading “particle size: 26.57 μm.”

The same D50 can describe different distributions

Two powders can share a D50 while differing at the fine and coarse ends. The following hypothetical values illustrate the distinction. They are not test results for Zhongan Copper or another supplier.

Both volume medians are 25 μm, but sample B has a lower D10 and a higher D90. A comparison sheet that records only D50 would miss that difference.

Span provides an additional description of the relative width between these percentiles:

Span = (D90 − D10) / D50

For these hypothetical values, span is 0.8 for A and 2.4 for B. HORIBA discusses this calculation in its guide to setting particle size specifications.

Span is a distribution-width statistic, not a plating-performance score. The example demonstrates a difference between percentile positions; it does not establish which powder would perform better in a particular PCB plating line. Even similar D10, D50 and D90 values do not prove that all details of two distributions are identical.

Establishing a basis for supplier comparisons

A difference between reports needs to be investigated at both the sample and method level. Sampling, dispersion and measurement settings can affect a result. Without those details, it is difficult to separate a material difference from a difference in how the test was conducted.

Include the following information in the technical review:

Sampling and dispersion deserve particular attention. Malvern Panalytical’s laser diffraction method-development guidance discusses their contribution to reliable measurements. The number of decimal places printed in a report is not a substitute for that method information.

Where a buyer and supplier use different instruments or methods, compare the conditions first. The laboratories can then determine whether comparison testing on traceable samples is needed to support subsequent lot reviews.

ISO 13320:2020 concerns laser diffraction particle size analysis. Its official abstract describes the method’s scope and model, but does not prescribe an optimum D50 or D90 for copper oxide used in PCB plating. A purchasing specification that references a measurement standard still needs to identify the particle size parameters and acceptance criteria agreed for the application.

Investigating a difference between two D50 results

Suppose a buyer receives one report with a D50 of 26 μm and another with a D50 of 34 μm. These hypothetical values illustrate a review procedure; they are not actual supplier results. The two numbers alone do not identify which material is preferable or explain the source of the difference.

For example, if one result is number-based and the other is volume-based, establish that mismatch before calculating a relative difference and using it to make an acceptance decision. Material differences and their relevance to a project can be evaluated once there is an appropriate basis for comparison.

If results for the same lot remain different under comparable conditions, the laboratories should review sampling, repeatability and original records. This article does not set a universal allowable deviation; the decision depends on the agreed method and project requirements.

Using particle size data in a PCB plating specification

A particle size report describes the size distribution obtained for a sample under the stated conditions. Suitability for a particular feeding, dissolution and plating system requires additional evidence.

For example, D90 and acid-insoluble matter are separate measurements. A size percentile cannot establish a residue concentration. The guide to acid-insoluble matter and particle residue addresses that part of a CuO material review.

Particle size data also cannot be converted directly into a dissolution time in a working bath. Dissolution comparisons require their own conditions, including the test solution, procedure and endpoint. See the comparison of acid dissolution and plating-bath dissolution for that distinction.

When establishing a purchasing specification, record the parameter, acceptance limit, method and sample identity together. If the project has no agreed particle size limits, procurement, quality and process teams should establish them using traceable samples and relevant qualification records. A measured value copied from one report does not, by itself, constitute an appropriate acceptance limit.

Suggested wording for a supplier document request

The following wording can be adapted for a sample request or technical-document review:

Please provide a particle size report corresponding to the sample under evaluation. Identify the sample, associated lot, test date and distribution basis, and include D10, D50, D90, the full distribution curve, and interval or cumulative data. If an “average particle size” is also quoted, please define that parameter.

Please identify the instrument, method and version, dry or wet procedure, dispersant and principal dispersion conditions. Include repeat measurements where available. If the method differs from that used in an earlier report, please describe the changes so that we can assess comparability.

The documents will support the sample evaluation. Particle size limits and acceptance methods for purchasing will follow the technical requirements subsequently agreed by both parties.

Where the project already has a particle size specification, send its parameter definitions and test method with the request so the supplier can respond on the same basis. Missing fields can be supplied in a separate method statement; a different report layout does not by itself require the whole report to be reissued.

Zhongan Copper’s document download center provides access to published material documentation. During technical evaluation, review the electronic-grade copper oxide powder specifications and confirm which reports, method details and lot documents apply to the sample. Final acceptance should follow the agreed technical requirements and applicable lot documentation.

Frequently asked questions

Which value should be used if the report and COA list different “average sizes”?

Start with the parameter definition. A D50 and a D[4,3] are different statistics and should not be compared as the same measurement. If both documents refer to the same parameter, check the sample, lot, method and conditions before agreeing which document and criterion govern acceptance.

Why might a microscope image show a different size from a particle size analyzer?

The measurement principles and statistical treatment may differ. Laser diffraction derives a distribution from a scattering model; image-based measurements require information about the objects observed, image selection and size statistics. Interpret each result with its method rather than treating numerical disagreement alone as proof that one is wrong. The ISO 13320:2020 abstract also notes that methods based on different physical principles can produce different results.

Can a micrometer-scale D50 establish the primary particle or crystallite size?

It cannot establish those dimensions on its own. The measurement object, dispersion state and relevant characterization evidence must be identified. The sample report discussed here gives a volume distribution under its reported conditions; it does not provide sufficient evidence to determine primary particle or crystallite size.