The PCB printed circuit glossary is designed to give you definitions to some of the words and phrases you will come across in doing business with Sunstone Circuits. While not exhaustive, it provides useful information about PCB circuits, circuit board design, and circuit board construction.
The ratio of the length or depth of a hole to its pre-plated diameter (Example. 0.062" thick board 0.0135" drill = aspect ratio of 4.59:1).
Based on the aspect ratio calculation a different product level will be determined. Below is the maximum aspect ratio allowed for each Product:
Designer tip: Minimizing the aspect ratio of the holes improves through hole plating quality and minimizes the chance of via failures.
The long standing industry standard base PCB thickness is 1/16 inch (0.062"). In addition to the 0.062" thickness the following thicknesses are also available for Limited Review products: 0.031", 0.047", 0.093", and 0.125". Overall thickness tolerance is generally within +/- 10% of the given thickness (for 2 and 4 layer boards) and 14% for 6 layer boards.
Additional thicknesses are available through PCBpro and Custom. Please select the "other" in the thickness dropdown menu and input your custom thickness. Include all layer thickness requirements on your drawing or "readme".
Technical information on our laminate materials.
Characteristic impedance extends the concept of resistance to AC circuits, describing not only the relative amplitudes of the voltage and current, but also the relative phases. When the circuit is driven with direct current (DC) there is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle.
The standard retention of quality documents (evidence of test, and inspection) for our product lines is as follows:
Limited Review (i.e. ValueProto and PCBExpress): Minimum of 90 days
*UL orders will retain the documentation for a minimum of 2 years.
Electrical continuity (opens) and Isolation (shorts) testing of Circuit Boards. A net list is created from the customer supplied gerber files and then electrically compared to the finished pcb. The soldermask layer acts as the mask to determine what points can be tested. In general, endpoints of all of the nets are programmed for testing unless they are covered in soldermask, in which case the closest testable point to the endpoint is tested. The standard testing parameters used are 100 Volts, Isolation Resistance of 10 M Ohms, Isolation Distance 0.050”, and Continuity Resistance of 50 Ohms.
Sunstone Circuits uses flying probe (fixtureless) technology to conduct our electrical testing. We recommend testing all surface mount boards and multilayer orders.
It's not possible to accurately test boards that have silkscreen on pads. It is highly recommended that the silkscreen clip option be selected on electrically tested orders.
RoHS compliant surface finish, that is also very planar (flat) and durable. ENIG is recommended for tight pitch, ICs and BGA type of technology. It provides a good solder joint, allows parts to sit very flat, will withstand multiple reflow cycles as well as storage of PCBs.
Electroless Deposition - The deposition of conductive material from an autocatalytic plating solution without the application of electrical current.
Immersion Plating - The chemical deposition of a thin metallic coating over certain basis metals that is achieved by a partial displacement of the basis metal.
A patterned arrangement of printed circuitry and components that utilizes flexible base material with or without flexible cover lay.
Flexible circuit boards are often used as connectors in various applications where flexibility, space savings, or production constraints make the use of rigid circuit boards impossible. In addition to cameras, a common application of flexible circuits is in computer keyboard manufacturing; most keyboards made today use flex circuits for the switch matrix. Contact our Support Team and we may be able to recommend a source for Flex parts.
A software tool used to view PCB design output prior to submitting it for fabrication. Do not just assume that the Gerber files will resemble your design file. There are quite a few places for errors to occur in the output of Gerbers.
Designer tip: May not be suitable for applications where multiple finger lengths are required.
With your Au selection, a standard 30-degree bevel will be added to your edge connector. We can also bevel at 15 or 45 degrees upon request. For multi-layer boards please insure adequate inner layer back set to allow for the bevel requested.
These are usually solid copper planes of a multi-layer board connected to power or ground.
Designer tip: Make any clearances on these layers 0.020" for PCBpro and custom 0.025" for Limited Review (diameter) over the finished hole diameter. Using these clearance guidelines will help you avoid shorts caused by manufacturing variations. (See “Clearances”)
Please clarify the correct polarity of your plane layers. The options for polarity are “positive” and “negative”. Positive images show all copper features as features on the gerber plot. Negative images show all features to be removed from the copper.
Designer tip: Any splits in planes should be at least 0.010” wide.
Routing layers composed of signal traces that are contained below the surface layers of your board. These layers are connected to the surface layers by plated through holes and/or vias.
We may remove any pads that are not connected to traces on your internal signal layers in order to expedite the imaging process on Full-Featured Orders. Many customers upload their files with these non-functional pads already removed, which expedites the tooling process. If for any reason, you do not wish these pads to be removed, please clarify this by listing it as a drawing note, or in a "readme" file.
We do not require you to map the layers from your files during the order process to help save you time. In order to be sure we build the layers in the correct order, provide a readme with the layer order or name the files in a logical manner. For example:
fab_dwg.grb (not needed if Sunstone Circuits manufacturing and inspection criteria are acceptable) May cause delay in processing your order.
The number of conductive layers required for your PCB order.
Designer tip: Text such as company name, logo, or part number that is correct reading on the top copper layer will insure the layers are oriented correctly. This orientation text can be placed inside or outside of the board outline. Text placed outside of the board outline will be used for reference only and deleted prior to manufacture. (see “Component Side”)
You can instantly quote PCBs with up to 20 layers online. For more than 20 layers a Custom Quote will need to be generated.
The limitations of a specific manufacturing process that is aimed at consistently producing product with a sufficiently high yield. These specific capabilities may be different for every PCB manufacturer, please follow these in the design portion of your project to help avoid problems down the road.
Sunstone Circuits manufacturing capabilities will provide more information.
Trace width and the space between traces are used to define the complexity of your design. We use this information for pricing and to properly align your order in our manufacturing products. The smaller or more tightly packed the features of your board are, the more difficult it will be to manufacture. When ordering your boards you will need to know the minimum trace size as well as the minimum copper to copper spacing present in your design.
Limited Review products have the capability of 0.005” trace/space while PCBpro can be ordered with 0.004” trace/space. If you need smaller traces or spaces please complete our request for custom quote form.
Due to processing considerations, for our customer’s design files that use cross hatching, our limit for online orders is .010” line/ .010” space cross-hatch pattern.
Designer tip: For traces embedded in ground plane we recommend a minimum spacing from trace to plane of 0.010”
See our manufacturing capabilities chart for more information.
A hole in a printed board that does not contain plating or other type of conductive reinforcement. Generally used for mounting of components to a circuit board or a circuit board to a larger portion of a project.
We recommend that you include a drill drawing to identify the non-plated holes in your design. Non-plated holes are NOT guaranteed through our ValueProto product line.
Non-Plated holes should maintain a minimum clearance of 0.010” from any conductive surface.
Sunstone offers 2 degrees of Engineering Levels. For each Level of Review there are different Order of Precedence that Sunstone use to manufacture these orders.
Limited Review Orders
Full Review (NRE) Orders
A hole with plating on its walls that makes an electrical connection between conductive patterns on internal layers, external layers, or both, of a printed board.
PCBpro Product: All drill sizes will be treated as PTH unless NPTH is specified in the Drawing, Print, Drill file, drill tool description text file, or identified with a special note, for example “ 0.125 holes to be non plated” In addition, landless holes identified in the Gerber files will be treated as non plated: holes without pads, holes designated with a crosshair target, or holes with a significantly smaller pad (i.e. 0.125" holes with 0.050" unsupported pads).
Limited Review Products: All holes in the drill file regardless of definition will be treated as plated holes. This means that they will have the hole size increased to accommodate plating, will be drilled at primary drill, and may or may not be plated (depending on presence of pads, proximity to copper features, or size of the drilled hole).
If drawing or tool description is different than the size specified within the drill file, we will use the drill file to determine finished hole size (For “Full Review” (NRE) these errors are reported for customer clarification before manufacturing can begin).
All orders placed as “1 layer” will be treated as single sided and the holes barrels will be non-plated.
The number of boards to be ordered.
To see the pricing matrix in the quote process, enter the approximate number of boards needed. The quantity can be changed at any step of the quoting process to meet your needs in terms of price and lead time.
ValueProto Product allows quantities up to 25 pieces. PCBExpress will allow up to 100 pieces and PCBpro will quote quantities up to 10,000 pieces. If you need larger quantities or would like to schedule out shipments, please use our request Custom PCB Quote form.
A text file included in the zip file, providing information needed to manufacture your order. Phone numbers or email addresses of designer or engineer contacts for this project should be included to expedite resolution of any potential manufacturing problems.
Below is a sample Readme:
Sunstone Order # (insert order number) ABC Company P/N AB C125 Rev A Please build a quantity of 100 pieces of this 6-layer board. We are requesting 1/2-oz. base copper weight, 0.062" thick on FR4 material, green solder mask, and white legend. The Gerber files included in this zip are: File Name (description): SR125.CMP Layer 1 (component side) SR125.gnd Layer 2 (ground layer) SR125.IN1 Layer 3 (internal signal) SR125.IN2 Layer 4 internal signal) SR125.VCC Layer 5 (power layer) SR125.SLD Layer 6 (solder side) SR125.CSM (Component-side solder mask) SR125.SSM (Solder-side solder mask) SR125.TSK (Component-side silkscreen/nomenclature) SR125.BSK (Solder-side silkscreen) SR125.DRL (Excellon drill file) SR125.TOL (Drill tool description) SR125.APT (Aperture information) SR125.DWG (Drawing or print) Any technical questions can be referred to email@example.com (your email address). My contact number is 555-555-1234 (your number).
Readme files in Limited Review orders will not be used in tooling of your order.
The number of iterations a particular part number has been through to reach the current level of development. We require a distinct combination of part number and revision for all new PCB orders.
In order to assure that the correct files are used in manufacturing, please indicate your revision number as well as the part number. The part and revision number should be included in your drawings and readme. Please change revision in all locations of your files, drawings, and readme’s to avoid confusion. (Most of the missed changes occur in the document header, or a generic print that was not updated.)
RoHS is the acronym for Restriction of Hazardous Substances. RoHS, also known as Directive 2002/95/EC, originated in the European Union and restricts the use of specific hazardous materials found in electrical and electronic products. All applicable products in the EU market after July 1, 2006 must pass RoHS compliance.
In an effort to support the RoHS initiative, Sunstone Circuits offers several options that comply with the directive. All of the laminate material, soldermask material, and silkscreen material supplied are compatible for assembly at lead free solder temperatures and do not contain (above the upper limits) any of the restricted materials. There are several options for surface finishes for RoHS compliance: Immersion silver, ENIG, OSP and electrolytic gold
RoHS compliance applies only to the printed circuit board “as shipped” and Sunstone Circuits retains no responsibility for RoHS compliance of the printed circuit board after any subsequent processing or component placement by our customers or their assemblers.
Marking ink used to identify components location during the assembly and troubleshooting processes. This can be placed on one or two sides of the printed circuit board depending on the board design and application.
Minimum line width for silkscreen legible printing is 0.006". Any lines drawn smaller may result in missing or illegible marking on your boards.
White is the standard silkscreen color used. Yellow and black are also available.
Printed circuit board with copper on only one side. Usually with through hole technology, the copper will be on the solder side, opposite any component placement. All through holes will be Non-plated. Solder pads should be oversized in order to provide adequate mechanical support for component leads. Pads that are too small can be easily torn from the pcb substrate.
With surface mount technology the copper layer is on the component side, or top of the board.
To avoid your job being put on hold, please use text to label your copper layer. This simple addition will avoid confusion about orientation of the copper and drill files. If your copper layer is to be on the component side, with components placed on top of the board as designed, text should be right reading. If copper layer is the bottom layer, opposite your components, text should be left reading (reversed) as seen looking down through the board. (see “Component Side”)
The maximum overall single board X and Y dimension measured at the supplied board outline. Irregularly shaped boards are measured from the farthest extents of the board outline.
All dimensions can be input in either inches (Imperial) or millimeters (metric).
The following are the board size limits for each product:
ValueProto: 12" x 14"
PCBExpress: 14" x 18"
PCBpro: 16" x 22"
Custom: > 16" x 22"
Defined as the size of the smallest drilled hole present in the design.
Please make sure that all of your holes are present in your Excellon drill file.
Soldermask serves 2 basic purposes. It protects the circuitry from solder during a wave solder process, keeps the solder from bridging gaps between nets, and it protects the copper from oxidation and corrosion.
Sunstone uses Tayio PSR BN-4000 liquid photoimagable (LPI) soldermask.
We recommend the following soldermask clearances for pads
Please note: While we make every attempt to leave a soldermask "dam" between surface mount pads, fine pitch areas may be relieved in strips. Our manufacturing process needs at least 0.005" ("Limited Review") or 0.004” (PCBpro) mask "dam" between pads in order to adhere to the board. Pad-to-pad spacing less than 0.013" may not have soldermask between them.
The sole purpose of a stencil is to transfer solder paste to a bare circuit board. A stainless foil is laser cut creating an opening for every surface mount device on the board. Once the stencil is properly aligned on top of the board, solder paste is applied over the openings (making a single pass, using a metal squeegee blade). When the foil is separated from the board, bricks of solder paste remain, ready for placement of the SMD. This process, as opposed to hand soldering methods, ensures consistency and saves time.
Foil thickness and aperture opening size control the volume of paste deposited on the board. Too much solder paste causes solder balling, bridging, and tomb-stoning. A lack of solder paste creates insufficient solder joints. All of which compromise the electrical functionality of the board.
Proper foil thickness is chosen based on the types of devices being loaded on the board. Component packages such as 0603 capacitors or 0.020” pitch SOIC’s, will require a thinner stencil than larger packages such as 1206 capacitors or 0.050” pitch SOIC’s. Stencil thickness ranges from 0.001” to 0.030”. The typical foil thickness used on the majority of boards is anywhere from 0.004” to 0.007”.
A method of forming an array of PCBs for automated assembly, utilizing a routing bit. A 0.100” routing path is formed around the perimeter of your board, leaving a narrow, (usually 0.100” wide) tab of material attaching the PCBs to each other and to the panel border. Tab-route is available through PCBpro and Custom Quote Product lines and requires an NRE.
When this service is selected on the order form, we will step and repeat individual images to fill a 12"x14” (approximately) panel. These panels will have a standard space of 0.1” apart, with 4 (0.1”) tabs positioned at our discretion along the edges, and surrounded by a 0.5" border.
If you have specific panel requirements such as “Perf” holes, Fiducials, or tooling holes, you will need to provide a detailed panel drawing with your board files.
In the printed circuit board production process there are process variation and equipment capabilities that can add some degree of error to a specific step. Some of these are drill machine X & Y true positional tolerance, drill bit deflection, layer to layer registration, rout tolerances and plating allowances. The specific values will vary by board manufacturer.
The following tolerances have been calculated based on all of the tolerances that may affect the items and ask that printed circuit board designs allow for these processes (to list just a few see manufacturing capabilities for a complete list):
These are the conductors of the printed circuit board. Limited Review products have the capability of 0.005” trace/space while Pcbpro can be ordered with 0.004” trace/space. If you need smaller traces or spaces please complete our request for Custom Printed Circuit Board Quote form.
Due to processing considerations, for our customers design files that use cross hatching, our limit for online orders is 0.010” line/ 0.010” space cross-hatch pattern.
Designers Tip: For traces embedded in ground plane we recommend a minimum spacing from the trace to the plane of 0.010”
Rather than completing a route path around the board edge, the edges are "scored" to allow breaking boards apart after assembly. This is another way to palletize / panelize the boards (see Tab Routing).
This method creates two beveled scoring lines along the perimeter of your boards. This makes it easier to break apart the boards at a later date. You would receive your boards in panel form like tab routing (see Tab Routing). Be sure to check with your assembly house for any special needs they might have.
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Sunstone Circuits® is the established leader in providing innovative and reliable printed circuit board (PCB) solutions for the electronic design industry. With over 40 years of experience in delivering high quality, on-time PCB prototypes, Sunstone Circuits is committed to improving the prototyping through production processes for the design engineer from quote to delivery. With Around the Clock support, Sunstone Circuits provides unparalleled customer service and leads the industry with a real On-Time Guarantee that is the first of its kind.