Printed Circuit Boards (PCB) Glossary
This 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.
Scroll down or choose the letter below to find your specific definition request.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Aperture Information
This is a text file describing the size and shape of each element on the PCB printed circuit boards. These are also known as D-code lists. These lists are not necessary if your files are saved as Extended Gerber with embedded Apertures (RS274X).
Annular Rings
The copper pad area that remains after a hole is drilled through the pad, measured from edge of hole to edge of pad.
Your inner and outer layer pads should be at least 0.018" larger than the finish hole size (0.010” for vias). If your design has any pad to trace junction minimum requirement, add that to the above numbers [0.018" pad + 0.002" junction should have 0.020" pad]. This will provide a 9mil annular ring for component pins, 5mil annular ring for vias.
Designer tip: Try using teardrop shaped pads. They offer a more robust design to accommodate for drill registration and / or Image shift during manufacturing and will help keep a IPC–A-600 Class II compliant, = 0.002” not reducing trace width more than 20% at trace/pin junction.
Aspect Ratio
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).
Maximum aspect ratio allowed for Sunstone Circuits manufacturing is 6:1.
Designer tip: Minimizing the aspect ratio of the holes improves through hole plating quality and minimizes the chance of via failures.
Board Thickness
The standard base thickness is 1/16 inch (0.062"). The following thicknesses are also available through Full Feature Product: 0.031", 0.047", 0.093", and 0.125". Overall thickness tolerance is within +/- 10% of the given thickness (for 2 and 4 layer boards) and 14% for 6 layer boards.
Additional thicknesses available through Custom Quote or, choose "Design Review Plus" option and select the closest thickness on the dropdown menu. Include all layer thickness requirements on your drawing or "readme".
Technical information on our laminate materials.
Build time
The cutoff time for receiving orders and files for Full Feature Product is 2:00 pm (PST) Monday through Friday and noon (PST) for Quickturn Product . Some files have been known to take 45 minutes to navigate the web, so please allow for this. Build time starts the following business day, unless a "hold" occurs.
Clearances
A clearance (or isolation) is a term used to describe the space from a power or ground layer to a plated through hole. To prevent shorting, ground and power layer clearances need to be a minimum over the finished hole size of 0.020” for Full Feature Multilayer PCB and 0.025” for PCBexpress quickturn printed circuits.
Component Side
In order to build your printed circuit board correctly, we must be able to identify the correct orientation of your design. Component, layer 1, or 'top' layer should read in facing up. All other layers should line up as though looking through the board. Please use layer designators, pass through marks, or correct reading layer text.
Continuous Outline
The outline or cut line for the printed circuit board made from a single continuous line. This line may not contain any broken/overlapping lines and/or improperly drawn arcs. The outline describes the shape of the board and is required for creating the route program.
Controlled Impedance
The electrical result of manufacturing a circuit board to meet characteristic impedance specifications. Combination of copper thickness and line width as well as the dielectric thickness and properties of the base material all contribute to the impedance value. The following is a good resource for calculation of impedance: http://www.mantaro.com/resources/impedance_calculator.htm.
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.
Copper (Finished Copper) Weight
This is total thickness of copper on the board surface. The value is determined from the copper foil thickness, plus plated copper, minus copper removed during surface preparation. Copper weight is measured in oz /sq foot. 1 oz = a minimum of 0.0012” thickness.
We offer finished copper weight of 1-oz., 1.5-oz., and 2.5-oz. If you need a different finished copper weight, please complete our Custom PCB Quote form.
CTI
The voltage which causes tracking after 50 drops of 0.1% ammonium chloride solution have fallen on the material. The results of testing at 3 mm thickness are considered representative of the material's performance in any thickness.
Tracking is an electrical breakdown on the surface of an insulating material. A large voltage difference gradually creates a conductive leakage path across the surface of the material by forming a carbonized track.
Performance Level Categories (PLC) were introduced to avoid excessive implied precision and bias.
Cut Lines
The cut line will be used to program the router path and it represents the circuit board outside edge. The tolerance on route dimension is +/- 0.010". It is recommended to keep outer layer copper 0.010” and inner copper 0.020” from the cut line to avoid exposing copper at the board edge.
Date Code (Full-Featured)
Marking of products to indicate their date of manufacture. It can be etched in copper, or printed during the Silkscreen process (default).
Design Review
As part of the Full-Featured Service we conduct a 25 point pre-engineering design review with a personalized report listing any DFM violations. Sunstone will give you the option to proceed "as is" or upgrade to “Design Review Plus”.
Design Review Plus
In addition to the 25 point Design Review , Sunstone’s experienced pre-engineering and CAM team will work with you to resolve any non-conforming findings, and will make the necessary edits to meet manufacturing requirements. A copy of modified Gerber files will be sent to you for your records.
Document Retention
The standard retention of quality documents (evidence of test, and inspection) for our product lines is as follows:
- Quickturn: 90 days
- Full-Featured: 3 Years
- Custom Quote: 5 Years
Drawing or Print
Sunstone orders do not require drawings or prints. If a drawing is provided with the order, the order form will override any details or notes on the drawing that deviate from Sunstone Circuits online capabilities and inspection criteria. The order form placed with each order is the governing document for orders placed on the web site.
Drill File (aka. Excellon Drill File)
This is an example of an Excellon drill file. It will have X & Y coordinates with tool sizes viewable in any text editor. This is the file that governs your finished hole sizes and locations.
A Sample Excellon File:
M48
INCH,LZ
T01C0.015
T02C0.031
T03C0.034
T04C0.037
T05C0.052
T06C0.058
%
T01
X00165Y-03805
X0018Y-03235
X00265Y-00704
X00281Y-01349
X00302Y-03816
Drill Tool Description
Text files describing drill tool number, corresponding size, quantity, and if the holes are to be plated or non- plated. (see “Plated through holes (PTH) – Non-Plated through holes (NPTH))
Electrical Test
Continuity and Isolation testing of Circuit Boards. A netlist 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 can be tested. In general, endpoints of all of the nets are programmed for testing unless they are covered in soldermask. 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 employs two methods to conduct electrical test 1) flying probe (fixtureless) and 2) the bed of nails grid tester (requires a fixture). We may choose to test your boards either way. We recommend testing for 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.
Embedded Traces
A trace that is surrounded by ground fill. These types of features have different manufacturing characteristics that do not behave as traces grouped in tight runs do. The etching of this type of feature is slower and as a result we request that a minimum of 0.010” spacing be used from trace to ground fill.
ENIG (Electroless Nickel Immersion Gold)
RoHS compliant surface finish available on Full-Featured and Custom Quote Products .
- 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.
Excellon Drill File
See drill file
Files: Gerber
TThe Industry standard format for files used to generate artwork necessary for circuit board imaging. Sunstone’s preferred Gerber format is RS274X, which places aperture information in the header of each gerber layer file (see Aperture information).
If files are not saved in RS274X, Sunstone will need one aperture list sent with the files.
When your software outputs more than one aperture list we may place your order on hold until we receive your instructions or correctly formatted files.
Files: Ivex
We can output the Gerber RS274X and Excellon Drill files from your Ivex .brd file at no additional charge. If you choose this option, we will hold your order until you approve the Gerber files generated. Gerbv is a free gerber viewer that will allow you to preview the production files as interpreted by our plotting software. It is highly recommended that you add text to the top layer of any IVEX file to insure that the orientation of your design is correct. Using layer designators is another option.
Files: Eagle
We can output the Gerber RS274X and Excellon Drill files from your Eagle.brd file at no additional charge. Gerbv is a free gerber viewer that will allow you to preview the production files as interpreted by our plotting software.
Files: Protel
You can output the Gerber RS274X and Excellon Drill files from your Protel file at no additional charge. Gerbv is a free gerber viewer that will allow you to preview the production files as interpreted by our plotting software.
File Submission
Files that are not specifically used in your design, and or an incomplete file set can add delays to your order. Insure that your submitted files are complete and do not contain extraneous files. When ordering a 4-layer board with Soldermask and one side Silkscreen, send in 7 gerber layers and an excellon drill file.
Flex
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. Flexible circuits are available through the Custom Quote Service.
Gerber Viewers
A software tool used to view PCB design output prior to submitting it for fabrication. There is a free tool available called Gerbv. Use the free Gerbv file viewer to confirm your files will be interpreted correctly prior to uploading. If you can load them using Gerbv, then we can too. A little extra time spent setting up your software outputs, and confirming they load correctly into Gerbv will insure a working board that will be shipped when you need it.
Download Gerbv:
http://sourceforge.net/projects/gerbv/
Gold Fingers (Linear Inches)
EEdge connectors electroplated with nickel (Ni) and gold (Au), good for wear type applications available for Full-Featured and Custom Quote Product. (Approx. 200 u” Ni / Min. 30 u” Au). Utilizing industry standard tie-bar plating protocol to allow electro plating of Ni and Au after etching. Price is calculated on the distance (linear inches) between the outside edges of the outermost connector contacts.
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 for the bevels.
Gold finger connectors typically have the leading edge beveled in order to ease insertion to the mating connector. When this happens, inner planes can have exposed copper if they aren’t pulled back from the edge sufficiently. We will pull your inner layer copper back as shown at the right above in order to avoid having exposed copper at this location. Exposed copper can cause a direct short across all terminals of your connector as it is inserted
HASL (Hot Air Solder Level)
The process of adding solder to the exposed copper features of the circuit board. The ratio of Tin to Lead in the deposit is approximately 60%/ 40%. Finished boards are dipped in a molten solder bath and passed through a high pressure stream of hot air to remove excess solder, resulting in a uniform solder layer being applied to all exposed copper surfaces.
Individual Route
Cutting of the circuit board to match the outline layer provided. There must be a continuous board outline for our Quickturn product. Boards will NOT be delivered in a multi-board panel for automated assembly.
Internal Signal Layers
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.
Inspection Guidelines
Our inspections and conformance criteria are setup based upon “IPC-A-600 Class II.” The inspection methods that we use to insure the quality of your orders can be accessed on our inspections guidelines page.
Internal Power and Ground Layers
These are usually solid copper planes of a multilayer board connected to power or ground.
Designer tip: Make any clearances on these layers 0.020" for Full Featured and 0.025" for Quickturn (diameter) over the finished hole diameter. TUsing 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.
Layers
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”)
The Custom Quote form can quote up to 14-layers. If your board has a higher layer count, please complete our online Custom Quote form.
Layer Sequence
Our online order form will ask for artwork layer to file name mapping. This form will appear after you upload files to the website. Please fill this form out accurately to ensure that your board layers will be assembled correctly.
It is very helpful to have files named logically, for example;
copper_top.grb
inner1.grb
inner2.grb
copper_bot.grb
silk_top.grb
silk_bot.grb
smask_top.grb
smask_bot.grb
paste_top.grb
paste_bot.grb
ncdrill.txt
drill_dwg.grb (not used for quick turn)
fab_dwg.grb (not needed if Sunstone Circuits manufacturing and inspection criteria are acceptable) May cause delay in processing your order.
Layer construction for Multilayer designs
The specified thickness and makeup of the different layers contained in a multi-layer printed circuit board. (see. Construction )
Lot Code
Some Customers require a manufacturer's lot code to be placed on the board for future tracking purposes. A drawing can specify the location, what layer and if it is to be in copper, solder mask opening, or silkscreen (default). This option is available on our Full Featured and Custome Quote products. The default format is a 4 digit number that contains the week and year. Example 3809 would be week 38 2009.
Manufacturing Capabilities
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 at all manufacturing locations, please follow these in the design portion of your project to help avoid problems down the road.
Sunstone Circuits manufacturing capabilities can be found at this link; http://www.sunstone.com/pcb-capabilities.aspx
Minimum Traces & Spacing
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 process. 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.
Quickturn product has the capability of 0.006” trace/space while Full-Featured can be ordered with 0.005” 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.
Non-Plated Holes
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 for Full Featured orders. Non-plated holes are NOT available through our Quickturn product line.
Non-Plated holes should maintain a minimum clearance of 0.010” from any conductive surface.
Non-Recurring Expense (NRE)
Refers to the cost of creating a new product, which is paid up front. Contrast with "production cost," which is ongoing and based on the quantity of material produced. For example, in the semiconductor industry, the NRE is the cost of developing the circuit design and photomasks; the production cost is the cost to manufacture each board.
Non-Supported Holes
A hole in a printed board that does not contain plating or other type of conductive reinforcement. See ‘non-plated holes’
Number of Holes
This is the total number of holes to be drilled in the board. Please be aware that your board price might change if the number of holes ordered is significantly different than the number of holes contained in your file set.
Order of Precendence
Custom Quote:- Customer supplied info (P.O., print, readme)
- Sunstone generated Order form
- Customer Specific Specification
- Order form
- Customer supplied info (P.O., print, readme)
- Customer Specific Specification
- Order form
- Sunstone Website
Pad
A portion of a conductive pattern usually, but not exclusively, used for the connection and/or attachment of components.
Part Number
The name or number associated with your printed circuit board design. We use your part number throughout the entire order process for your convenience.
PCB123
Printed circuit design software developed by Sunstone Circuits for use in the Sunstone Circuits ECOSystem. This software is Free to download and use, it is integrated into the Sunstone Circuits manufacturing process.
Plated Through Holes (PTH)
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.
Full Featured 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).
PCBexpress quickturn Product: 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 “Design Review” 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.
Quantity
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.
Quickturn Product allows quantities up to 100 pieces. Full Feature will quote quantities up to 15,000 pieces. If you need larger quantities or would like to schedule out shipments, please use our request Custom PCB Quote form.
Readme File
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 johndoe@abc.com (your email address).
My contact number is 555-555-1234 (your number).
Readme files in PCBexpress quickturn orders will not be used in tooling of your order.
Revision
The number of iterations a particular part number has been through to reach the current level of development.
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)
Rogers Material 4350
The demand for Rogers materials is continuously on the rise. In their quest to continue being the easiest PCB company to do business with, Sunstone has responded to that demand and is now offering RO4350 on 2-Layer quickturn prototypes. Boards can be purchased in quantities of up to 25 per order, and will be shipped to customers within 24 hours of purchasing. With the wireless communications industry rapidly evolving, this type of demand is becoming extremely common. Nearly all radio frequency (RF) devices used for test equipment specify Rogers materials. With its impressive and efficient dielectric constant, Rogers PCBs allow for very little current impedance. As a result, it has become the material of choice for designers developing high speed circuits.
RoHS (Reduction of Hazardous Substances) Compliance
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 (Full Feature only), OSP (Full Feature only), electrolytic gold (Full Feature only)
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.
For more information regarding RoHS, please visit RoHS FAQ’s
Silkscreen, Nomenclature, or Legend (Artwork)
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 through our Full Featured product.
Silver
Immersion silver is one of the RoHS compatible surface finish alternatives available.
Single-Sided Boards
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”)
Size X & Y (board size)
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 are in inches (please convert from metric for your order form). Please note, our maximum X & Y configuration is 12” x 14" for Quickturn and 14”x 18" for Full Featured.
If you require larger boards, please submit a Custom Quote.
Smallest Hole
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.
SMOBC
Acronym for Solder Mask Over Bare Copper.
Solder Mask
A heat resisting coating material applied to selected areas to prevent the deposition of solder upon those areas during subsequent soldering.
Soldermask also protects the conductors from handling and use.
Green Tayio PSR-4000 HG Liquid Photo-imageable (LPI) is our default process. Other colors available through Full Feature or Custom Quote include red, black, blue, white and clear.
Solder Mask (Artwork)
We recommend the following soldermask clearances for pads
- PCBexpress quickturn: +0.006”to 0.010” (diameter).
- Full Feature: +0.00 to 0.010” (diameter).
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" (Quickturn) or 0.004” (Full Featured) 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.
Solder Mask Color
Green is the default solder mask color. We have additional options available through Full Featured and Custom Quote Product lines. These colors are red, black, blue, white and clear.
Standard 24 Drill Sizes
In order to keep lead times to a minimum only 24 drill sizes are available for ValueProto Products. A chart to reference your designed drill size to a nominal finished hole size is available at: http://www.sunstone.com/products-services/quickturn-proto-boards/drill-file-pad-clearance-setup.aspx#pad
Stencil
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”.
Surface Mount Pitch
The pitch of the surface mount is defined as the dimension, in inches, from center to center of surface mount pads. (When the conductors are of equal size and their spacing is uniform, the pitch is usually measured from the reference edge of the adjacent conductors.) Standard pitch is >0.025", fine pitch is 0.011"-0.025", and ultra fine pitch is <0.011”.
Tab Routing (with & without perforation holes)
A method of forming an array of PCBs for automated assembly, utilizing a routing bit similar to a wood router. 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 Full Featured and Custom Quote Product lines.
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
Tolerances
In the printed circuit board production process there are: drill machine X & Y true position capability, drill bit deflection, image film stability, Multilayer layer to layer tolerance, 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):
- Outer layer pads should be 0.017” more than the drill holes (if you have to go a mil or two less try using teardrop shaped pads to limit the amount of breakout that could occur at the pad / trace junction).
- Inner layer clearances should be 0.025” more that the drill holes.
- Copper features should be 0.010 away from the rout line for outer layers, and 0.025" for inner layers.
Traces and Spaces
These are the conductors of the printed circuit board. PCBexpress quickturn product has the capability of 0.006” trace/space while Full Feature Multilayer PCBs can be ordered with 0.005” 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”
UL (Underwriters Laboratory) Marking
Sunstone’s UL File Number E58527. We will mark your boards with our UL identification and 94V-0 flammability rating. ( Full Feature Multilayer circuit boards and Custom Quote Products)
Vias
Holes for which are designed to move current from one side of the board to the other and not to have a component or lead inserted.
V-Scoring
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.
Zip File
All files needed for the processing of your printed circuit board order must be compressed in a zip file. Due to the large amount of orders received, we are not able to accept individual layer files sent to us. Winzip or Pkzip can be downloaded from our pcb links page.