The customer audit asks a question your specification sheet cannot answer: how often do you run an ionic contamination test on washed boards? None of our 22 published product pages states a sampling interval. The interval is a risk decision, and this article sets a starting frequency you can defend, then tighten with data you already have.
Here is the evidence. On 4 November 2026, the full range went under the scanner: 22 pages, body copy and specification tables, searched for anything that sets a verification interval or names a monitoring instrument. The count: zero pages publish a sampling or verification interval. Three pages publish resistivity data you can trend between tests. One page — the CQ-C758, our general-purpose board cleaner — uses the words “ionic cleanliness” in its copy, promising stable results batch after batch, without naming a frequency. Where an instrument exists, it is specified; the interval is left to you. Source: scan of all 22 published CHUANGQI pages, 4 November 2026.
Key takeaways
- No specification sheet sets the interval: 0 of 22 product pages publish one.
- Flux class, board criticality, process stability and the next process step set the frequency.
- Trend rinse-water resistivity between tests — one published monitor covers 0–18 MΩ.
- Tighten the interval after any fluid, recipe or board-family change.
- A frequency you can justify beats a number you copied from someone else’s audit.
What 22 Product Pages Publish About Verification
The audit found two kinds of verification content. The first is instrumentation: one machine in the range ships with a resistivity monitor built in. The second is rinse-water quality: two washers publish the resistivity of their DI (deionized) water supply. Both are measurable, both can be logged per cycle, and neither tells you how often to pull a finished board for residue testing. That gap is what the table below shows.
| Machine | Published verification-related row | What it gives you |
|---|---|---|
| CQ-C740 Electric Stencil Cleaning Machine | Resistivity monitor, range 0–18 MΩ | An instrument to log every cycle (the published figure is a range dial, not a pass mark) |
| CQ-C9610 Inline PCBA Water Cleaning Machine | DI-water inlet above 15 MΩ (1.0 m³/h service) | A rinse-water quality figure to trend against |
| CQ-C743 Offline PCBA Cleaning Machine | DI-water inlet above 15 MΩ (0.5 m³/h service) | The same trend figure on a batch platform |
Source: CHUANGQI product page audit, 4 November 2026. 19 of 22 pages publish neither an instrument nor a water-quality figure for verification purposes.
Read the two figure types for what they are. A monitor with a 0–18 MΩ range is a measuring span, not an acceptance criterion (a reading of 18 MΩ says nothing about the residue on yesterday’s boards). A DI-water resistivity above 15 MΩ is an inlet specification — the quality of water entering the machine, not the cleanliness of boards leaving it. Between them they give you a trend signal, and trend signals are what let a sampling interval stay wide without getting dangerous.
Four Factors That Set Your Sampling Frequency
Flux activity. Water-soluble and activated fluxes leave residues that conduct; they demand tighter verification than mildly active formulations run under their intended conditions. If your paste or wave flux changed this quarter, your interval from last quarter is obsolete.
Board criticality. Boards headed into automotive, medical or industrial-control assemblies inherit the audit burden of the end product. Sampling that satisfies a consumer board will not satisfy a customer whose own certification depends on your records — where an acceptance line comes from is covered separately.
Process stability. A wash whose recipe, detergent and filter condition have been unchanged for weeks has earned a longer interval. A line where fluid is changed, topped up or refreshed operates against a new baseline — when to change the cleaning solution walks through the signals.
The next process step. Conformal coating, wire bonding, potting and connector assembly all form bonds on the surface you washed. The closer the next step sits to the surface, the more often the surface needs proving.
| Situation | Starting interval (to validate on your line) |
|---|---|
| New process, new board family, or any fluid change | Every lot, until the trend holds for two weeks |
| Stable process, high-criticality boards | Weekly |
| Stable process, moderate-criticality boards | Fortnightly, plus after every change |
| Stable process, low-criticality boards, clean trend | Monthly spot check |
Starting points for a first quality plan, not acceptance criteria — no standard fixes these intervals, and your own trend data and customer contracts override the table.
What to Trend Between Samples
- Resistivity monitor — the CQ-C740 publishes a monitor spanning 0–18 MΩ; log the reading each cycle and act on drift, not on single values.
- Rinse-water inlet figure — the CQ-C9610 and CQ-C743 specify inlet DI water above 15 MΩ; falling readings between board tests point at bath loading before a board ever fails.
- Release records — the station records described in the cleaning-verification release checklist are where those readings live, so the trend survives a change of operator.
This method is not suitable for three cases. Contracts that name the test frequency and the method: the contract wins, full stop. Safety-critical boards whose customer drawing specifies sampling: follow the drawing. Processes in the middle of a chemistry or recipe change: sample every lot until the process is re-stabilized, then restart the table above. Our own factory chain works the same way — every machine we ship passes a test-board ion cleanliness verification inside a fixed outgoing sequence, because a stable process still needs points of evidence.
Frequently asked questions
How often should you run an ionic contamination test?
Start from the four factors: flux activity, board criticality, process stability and the next process step. The table above turns them into starting intervals — every lot for a new or changed process, then weekly to monthly as the trend proves stable.
Is a ROSE test the right check for every batch?
ROSE testing is one route, not the only one. The current edition of IPC J-STD-001 (Revision H) names alternative acceptance routes instead of a single numeric limit, so the method you cite in your quality plan matters as much as the count. Name the method, the board family and the acceptance route together, or the result will not survive a customer audit.
Does the washing machine guarantee cleanliness?
No. A washer publishes instruments and inlet specifications; the result depends on the recipe, the fluid condition and the verification you run around the machine. That is why the interval exists as a separate decision from the purchase.
What does a resistivity monitor tell me between tests?
It tracks the rinse stream, not the boards. A drifting reading warns that bath loading or inlet water quality is moving, which tells you to pull a board sooner than the calendar says. Treat it as a smoke detector, not a certificate.
If you are building the verification chain around a new washer, send the board family, the flux in use and the interval you are considering through the cleaning-machine enquiry form — a process engineer comes back with a machine recommendation, quote within 24 hours.