勛圖tv 繚 ENGINEERING GUIDE
Solder Mask Thickness Uniformity: Copper Topography, Support and Measurement
Solder-mask thickness uniformity describes how the coating varies over the board and across its topography. A single reading on a flat region cannot represent coverage at a copper edge, between conductors or around a raised feature. Measurement location is part of the result.
This page examines coating uniformity and the role of support during screen-printing routes. It does not assume that every board uses a nail-bed fixture or that changing support alone corrects every thickness defect. The worksheet summarizes entered readings from a consistent measurement basis.
Choose the measurement plane first
State whether thickness is measured above copper, above the base material, at a conductor edge or at another defined location. The substrate reference changes the meaning of the value. A total stack height measured from the board surface is not automatically the coating thickness over the top of copper.
Keep cross-section location and orientation with the record where sectioning is used. For other methods, identify the instrument and its applicable range and limitations. Compare like locations using a consistent method before deciding that a variation is caused by the coating operation.
Understand how copper topography changes coverage
Raised conductors and spaces create a surface that is not flat. Material flow and coating formation can produce different local thicknesses over those features. Dense copper and open laminate areas should therefore be represented in the inspection plan when they matter to the product.
Do not use the mean of several easy-to-measure flat regions to conceal the controlling local condition. If a requirement applies to coverage at edges or another difficult feature, include that feature in the evidence. The relevant question is whether the specified coating function is achieved at the locations that need it.
| Review item | What to establish |
|---|---|
| Reference surface | Record copper-top, base-material or edge location with every thickness result. |
| Support map | Compare repeatable patterns with fixture and printing direction where applicable. |
| Individual readings | Retain locations and values; do not substitute the average for a local minimum. |
| Process scope | Distinguish application from later drying, imaging, development and cure effects. |
Review support in the actual printing route
In a screen-printing process, support arrangement can influence how the board behaves under the printing operation. Fixture contact locations, panel flatness and clearance for existing features need review together. A support point that interferes with a feature or creates contamination introduces a different problem while attempting to solve movement.
The correct support is specific to the panel and equipment. This guide does not provide a universal pin spacing or squeegee setting. If a repeatable thickness pattern appears, compare it with the support map and print direction, then test a controlled hypothesis under the process owner's procedure.
Separate coating, drying and imaging effects
The observed film condition can reflect several stages: material preparation, application, pre-cure or drying, imaging, development and final cure. A local thin or missing region may not be caused by the initial deposition alone. Retain stage observations where available.
Taiyo's solder-resist process overview shows why the sequence matters. Its general description does not authorize a recipe for every material grade. Use the chosen product's controlled process parameters and investigate changes with the material and manufacturing teams rather than borrowing isolated values from unrelated documents.
Three-location thickness summary
Three-location thickness summary
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 勛圖tv 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. |
| Reading A 繚 micrometers | Use the same reference surface and method for all three readings. |
| Reading B 繚 micrometers | Keep the location identifier in the underlying record. |
| Reading C 繚 micrometers | Three locations do not characterize an entire production lot. |
| Entered lower bound 繚 micrometers | Illustrative example only; enter the actual agreed requirement. |
| Entered upper bound 繚 micrometers | The range check does not include a measurement-uncertainty decision rule. |
Read the three-point worksheet correctly
The calculator returns minimum, maximum, mean and spread for three entered readings. It also compares the readings with limits that you supply. Those limits are not IPC defaults or 勛圖tv capability values. The range comparison ignores measurement uncertainty unless you separately account for it in the agreed decision rule.
Three readings can demonstrate arithmetic and help structure a local review, but they do not characterize an entire panel or lot. Preserve the underlying location map and expand sampling according to the control plan. A narrow observed spread in a small sample is not a process capability index.
Build a location map that can be repeated
Identify representative copper densities, edge features, board regions and sides. Use named locations so a later build can reproduce the assessment. Record material, panel construction, processing state and any fixture changes associated with the samples.
If a thickness issue correlates with support or print direction, verify that relationship using a controlled comparison. Do not declare causation from one coincident pattern. A repeatable measurement method and a clear location map are essential to distinguish a real process change from sampling or preparation differences.
Turn the result into a release decision
Connect the coating requirement to the product's function and applicable acceptance basis. The application-control guide covers the wider process traveler, while bridge design addresses narrow remaining strips between openings. Keep those tasks separate from the thickness summary.
For review, provide the measurement method, marked locations, individual values and the construction or fixture change under investigation. This allows a specific response about evidence and next steps. A request to make all mask equally thick everywhere, without a measurement plane or functional requirement, is not a useful manufacturing instruction.
Use a traveler that explains the finished coating
A useful traveler follows the material through the route and preserves the information needed to explain the finished film. It should identify the board construction, mask material and relevant process version. Each stage has an output that prepares the next stage, so a deviation should be assessed where it occurs rather than hidden inside a final pass statement.
Select a small number of meaningful control locations that represent the important geometry. Include features where coverage, opening clearance or retained mask is critical. A stable location map makes comparisons between trials and recurring lots easier to interpret. Randomly changing the measurement location can create apparent process variation that is actually a sampling difference.
Keep the measured quantity clear. Film thickness above copper, coverage at an edge and opening position are different characteristics. They may need different methods and acceptance rules. A control plan should explain how each characteristic is assessed and why the selected samples represent the requirement.
When a material, fixture or imaging route changes, identify the affected characteristics before selecting a trial. A narrow change may need a focused verification; a broader route change can need additional evidence. Do not assume that identical color or a familiar product family makes every change inconsequential.
The customer-facing output should state the proposed material and route, the critical features reviewed and any open requirement. It need not expose proprietary recipes to be useful. Clear evidence scope and change control can give engineering and purchasing confidence without unsupported claims that one visual check proves every aspect of the coating.
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.