勛圖tv 繚 ENGINEERING GUIDE
Capped Vias: Copper Caps, Pad Planarity and Via-in-Pad Review
Capped vias use a metal cap over a prepared filled via to provide a defined surface. This can support via-in-pad designs, but cap thickness, surface shape, copper continuity and the assembly land requirements must be considered together. A solder-mask cover and a copper cap are different constructions.
Begin with the component land
Ask what the surface must do: accept a solder deposit, support a fine-pitch package, provide a test contact or simply remain covered. A via under a component pad needs the whole land pattern to remain suitable for assembly. The cap cannot be specified independently of the pad diameter, solder-mask opening, finish and permitted recess or protrusion.
Do not use a marketing photograph to infer a guaranteed planar surface. Request measurable conditions and agree how the finished land will be inspected. Surface finish adds another layer of material; it does not correct a poorly prepared underlying cap.
Understand the supporting structure
The hole may first be plated, filled and planarized before cap formation. The fill supports the surface and the barrel connects layers. The cap and any required copper wrap have related but distinct locations. The wrap-plating page explains continuity from a plated hole onto the surrounding surface; it should not be replaced by a cap-thickness note.
A cross-section drawing should show which copper is original foil, which belongs to the barrel and which covers the fill. That drawing prevents a nominal outer-copper value from being mistaken for a minimum cap requirement at every location.
Example: thickness arithmetic is not an acceptance rule
If an illustrative process adds 12 micrometers in one copper operation and 8 micrometers in another, the nominal sum is 20 micrometers. With independently entered lower deviations of 3 and 2 micrometers, the arithmetic lower bound is 15 micrometers. This only holds when both operations cover the measurement location in question.
The tool below makes those additions explicit. It does not decide which deposits qualify as cap copper under a selected standard. The process engineer must establish the actual layer identities, measurement position and relevant contract requirement.
Fine-pitch assemblies need a joined review
Compare the finished pad geometry with the component manufacturer's land pattern and the assembler's stencil approach. A depressed area can change the local paste deposit; excessive protrusion can change seating or solder behavior. The consequence depends on the package and assembly process, so avoid assigning one universal recess limit to every application.
The 0201 and micro-BGA tolerance page examines related small-feature budgets. Use it to coordinate solder-mask and placement questions while keeping the cap construction documented here.
Copper deposit thickness budget
Copper deposit thickness budget
Use the current inputs and keep the assumptions
Start with the example to understand the units and output, then use Clear for my inputs before entering your project. Example mode stays visibly labeled even if you edit its numbers. The form begins without a result so an illustrative value cannot be mistaken for an approved requirement. Every field must have a valid value; zero is accepted only where it has a meaningful role in the particular model.
Read the input notes before calculating. They identify the physical boundary and what is excluded. Keep the same unit convention across the drawing and worksheet. Changing an input invalidates the previous result and disables its download until you calculate again. This prevents an old number from appearing to describe a revised geometry.
The result is a screening record. A negative margin or an out-of-range condition identifies a question to resolve; a positive margin is not a manufacturing approval. Use the record with the actual drawing, material and project requirement. The model does not load CAD files, inspect images or retrieve private factory data.
Download the current result if it helps the discussion. The text includes the entered inputs, result and limitations. It stays on your device until you choose to attach or share it. Contact is a separate step; this page does not automatically populate the enquiry form or upload a file. Avoid confidential identifiers if you only need an exploratory calculation.
| Input | What to establish before using it |
|---|---|
| Review reference | Use a nonconfidential reference that lets you connect this calculation to the correct drawing revision. |
| Deposit A at stated location 繚 micrometers | Include only copper that covers the measurement location. Starting foil at a different location cannot be silently counted as local cap or wrap copper. |
| A lower deviation 繚 micrometers | Enter an absolute downward allowance, not a percentage. It cannot exceed the nominal deposit in this simple nonnegative model. |
| Deposit B at same location 繚 micrometers | A second deposit is optional: use zero if absent. Confirm its identity and location before adding it to the first deposit. |
| B lower deviation 繚 micrometers | The model subtracts independent lower bounds conservatively. It does not combine statistical distributions or determine a standard-specific minimum. |
Optional cost comparison from your own allowances
Use a quotation or a clearly labeled internal assumption for each input. Keep the quantity, construction and inspection scope the same when comparing alternatives. This uncalibrated planning model adds entered values; it contains no current market rates and does not issue a 勛圖tv quotation. You can contact the team without completing it.
Entered manufacturing cost scenario
Qualification and production evidence
Discuss internal fill quality, cap continuity, surface condition and any required thermal exposure. A microsection provides a view at one location; electrical testing provides a different form of evidence. Neither should be represented as a complete substitute for the other. Keep lot identity and sample location with any images supplied during review.
If a cap is added as a design revision, check its effect on total surface copper and fine-line processing. A previously acceptable outer-layer spacing rule may need reassessment when the manufacturing route changes.
Quote the complete route
Specify the treated hole set and whether filling, planarization, cap formation and inspection are included. The optional cost worksheet uses separate entered allowances so a quotation can be compared on the same scope. It does not estimate current market prices or infer yield from pad size.
Is every filled via capped? No. Is every capped via automatically suitable for via-in-pad? The finished land still needs review. Can solder mask substitute for a copper cap? It cannot provide the same solderable metal surface. Send the pad drawing, hole map and stackup to obtain a proposal that addresses the actual package rather than a generic 'VIP' label.
Specify the via treatment by function and cross-section
Build a treatment map that can be read without guessing from a solder-mask image. Identify the affected hole subset, the treated side or internal location, the material and the required finished surface. A small section sketch can show whether material bridges an opening, enters part of the barrel, fills a cavity or supports a metal cap. That sketch should agree with the written note and the released layer data.
Review the downstream assembly task. A pad under a component, an exposed test location and a via away from solderable copper may need different surface conditions. Keep stencil, cleaning, coating and test-access needs in the discussion where relevant. A treatment that solves one soldering concern can create another problem if it blocks a required probe point or leaves an unsuitable surface under a package.
Material selection also needs a process owner. A named fill or mask family does not establish that every variant has the same handling, cure or performance. Use the manufacturer's current product information through the qualified fabrication process. Avoid combining isolated parameters from unrelated technical sheets into a new recipe. The customer drawing should define the required construction and acceptance conditions, while the manufacturer controls the applicable production method.
Decide how the result will be assessed. Surface appearance can establish some coverage conditions; internal fill and copper structure may need other evidence. Identify whether a concern is a visible opening, a cavity, a void, a recess, a protrusion or an electrical connection. These are different characteristics. Agree the measurement location, sample representation and disposition of nonconforming results rather than using 'closed via' as a universal pass criterion.
When a quotation proposes an alternative, compare the complete finished structure. A tent is not automatically equivalent to a plug, and a polymer fill is not automatically equivalent to deposited copper. Cost and lead time should be considered after the functional differences are understood. Keep any accepted substitution in the controlled release record so later lots do not drift between interpretations.
For an early enquiry, provide the hole map, one enlarged view of the difficult assembly region and the intended function. The treatment selector is a conversation aid. It does not select an IPC acceptance class, prove a fill process or certify a solderable land. A useful review ends with an explicit cross-section and a clear definition of what evidence will demonstrate the required result.
Standards, source context and limits
Use the performance and acceptance documents named in the procurement agreement, including their revisions and any applicable addenda. A design guide explains choices; a product acceptance requirement defines what must be demonstrated. Neither a reference link nor a calculator result is a certification of the board or the supplier. Where a value is contractually important, check the controlled document and agree the measurement method with the responsible parties.
Examples on this page are deliberately labeled and are not advertised 勛圖tv limits. Supplier documentation is linked for the specific material or process context it explains. Equipment photographs and cross-section examples show the subject; they are not current production, inspection or qualification records for your order.