What Is A Silkscreen PCB?
Silkscreen PCB is a type of circuit that has a layer of solder mask traces that work as a reference indicator for PCB components.
The solder mask traces can have the logos, test points, component values, polarity, part numbers, warning symbols, etc. And they can create a connection path to communicate with each of the pin.
Silkscreen circuit boards are useful to assist in specifying the essential information of the circuit board.
Is There Any Difference Between Silkscreen PCB And Dupont PCB?
First, we check the construction materials.
The epoxy ink is used to make traces on the Silkscreen. On the other hand, Dupont material is made of either polyimide or copper-clad laminates.
The Silkscreen PCB’s solder mask is non conductive, Dupont material is Halogen-free.
The manufacturing proceed is very complex for silk screen circuit boards where laminating Dupont PCB is more easier than it.
If we think about the cost, Dupont materialrequires less cost and less effort than Silkscreen.
What Are The Components Of Silkscreen PCB?
Several components are on the silkscreen printed circuit boards according to the application demands.The following components are common for the silkscreen circuit to identify by the manufacturer and the end-users such as Manufacturer identifhers
5Warning signs like High Voltage
6.Print company logos, name
7.Version numbers like V2, V3, V4, etc.
Venture is a PCB manufacturer. We manufacture different types of PCBs such as flexible PCB, rigid-flex PCB, and etc.
Additionally, we are also supplying PCB Silkscreen. We supply our customers from all over the world and deliver them in the fastest way so that you can save time.
We can design your PCB Silkscreen depending on your specifications.
To send your design of PCB Silkscreen, feel free to contact us.
Your Leading PCB Silkscreen Stack-up Supplier in China
Venture is a manufacturing company that specializes in providing solutions for an extensive range of PCB silkscreen with excellent quality and high efficiency at competitive prices. We supply PCB silkscreen for a wide range of applications.
The silkscreen is used to identify components, warning symbols, test points, logs, parts of the PCB, marks, date codes, company logos, manufacturer marks, and etc. It is a layer of ink traces. Usually, silkscreen is applied on the component side. But using silkscreen on the solder side is also common.
Essentially, a detailed PCB silkscreen helps to locate and identify all the components.
The top layer of the PCB is the silkscreen. It serves as a reference indicator for placing components on the PCB. Usually, the graphics and text on PCB are printed with permanent non-conductive epoxy ink.
The standard colors we normally see are black, white, and yellow. Although these colors are available, the color is typically white.
There are three methods of silkscreening. First, manual screen-printing. Second is liquid photo imaging (LPI). And lastly, the direct legend printing (DLP).
Venture can provide silkscreen on your PCBs. We will do our best to meet your demands for silkscreens.
For more details, please contact us and we will be happy to answer your questions.
PCB Silkscreen: The Ultimate FAQ Guide
If you want to be an expert in PCB silkscreen, then read this guide.
It has all information you need to know about PCB silkscreen.
Keep reading to learn more.
- What Is PCB Silkscreen?
- Is There Difference Between PCB Silkscreen And PCB Legend?
- What Is The Purpose Of PCB Silkscreen Layer?
- What Is The Difference Between PCB Silkscreen And PCB Solder Mask?
- When Is Screen Printing Done In The PCB Fabrication Process?
- Which Side Of PCB Do You Apply Silkscreen: Component Side or Solder Side?
- What Information Does PCB Silkscreen Offer?
- What Is The Standard PCB Silkscreen Colors?
- Are There Other Custom PCB Silkscreen Colors?
- What Is The IPC Specification For PCB Silkscreen Thickness?
- How Do You Perform The PCB Silkscreen Printing?
- Which Are The Common PCB Silkscreen Printing Methods?
- What Are The Types Of Ink Used In PCB Silkscreen Printing Process?
- Which Factors Determine The Cost Of PCB Silkscreen Ink?
- Which Are The PCB Silkscreen Markings Employed To Accurately Mount Components?
- What Is The Recommended Font For PCB Silkscreen Layer?
- Which Are The Important PCB Silkscreen Guidelines To Follow When Designing Silkscreens?
- What Are The Important Parameters To Consider During PCB Silkscreen Printing Process?
- Which Equipment Are Used In Conventional PCB Silkscreening?
- What Is The Recommended PCB Silkscreen Line Width And Text Height?
- How Does Line Width Affect The PCB Silkscreen Printing Process?
- Should You Print PCB Silkscreen Over Solderable Surfaces?
- What Does Text Design Imply In PCB Silkscreen?
- How Do You Determine PCB Silkscreen Cost?
- Which PCB Silkscreen Marks Are Used For Troubleshooting And Testing?
- What Is The Recommended PCB Silkscreen Clearance?
- Which Are Some Of The Vital PCB Silkscreen Mistakes To Avoid?
- How Do You Mark Diode Poles On PCB Silkscreen Layer?
- What Is The Purpose Of Clipping In PCB Silkscreening Process?
- Which Are The Common PCB Silkscreen Symbols/Reference Designators?
- What Is The Commonly Applied Standard For PCB Silkscreen Symbols?
What Is PCB Silkscreen?
The PCB silkscreen encompasses the outer layer of a PCB with indicators you employ for reference when populating the board.
Some of these indicators include component values, test points, warning symbols, polarity marks, part numbers and logos.
Usually, you apply the silkscreen on the PCB component.
However, you find some boards with silkscreen on the solder surface.
The information on the PCB silkscreen is useful in PCB manufacture ensuring proper assembly of the board.
When making PCB silkscreen you employ a non-conductive epoxy ink with permanent property to mark out the graphics and text.
You find white ink commonly employed for PCB silkscreen with other colours such as black and yellow also possible.
Is There Difference Between PCB Silkscreen And PCB Legend?
PCB silkscreen and PCB legend are one and the same referring to the printed information on the board surface.
You can also refer to this layer as nomenclature and it allows you to place components on the board.
Information on a PCB silkscreen or legend encompasses reference designators, test points, pat numbers, component identifiers and even company logos.
There are different methods you can use to apply a PCB silkscreen or legend.
What Is The Purpose Of PCB Silkscreen Layer?
The PCB silkscreen is important for the following reasons:
- The PCB silkscreen defines the points of component placement on the board surface during assembly or population.
- When you have a PCB silkscreen, it allows engineers and PCB technicians to easily locate test points on the board surface.
Test points are useful when extracting measurements and carrying out troubleshooting.
- Information on the PCB silkscreen such as voltage values, current values and power values serve as warnings for shock or damage.
- A PCB silkscreen serves as a reference indicator allowing you to determine a component on the board and polarity arrangement.
- You employ the PCB silkscreen to give precise values of components such as resistors, transistors and capacitors.
Consequently, you prevent mismatching such components with lower or higher values.
What Is The Difference Between PCB Silkscreen And PCB Solder Mask?
The PCB solder mask is a polymer layer you apply over the conductive copper traces of a PCB.
The PCB solder mask protects these traces from oxidation during the soldering process and also the formation of solder bridges.
Solder bridges are conducive paths formed between adjacent solder pads that can result in shorts due to forming undesired electrical connection.
Consequently, using a PCB solder mask restricts the movement of solder.
You typically apply a PCB Silkscreen over the PCB solder mask to provide board information such as reference designators.
With a PCB silkscreen, you eliminate obscurity in terms of placing and identifying components, their values and polarities.
PCB solder mask
When Is Screen Printing Done In The PCB Fabrication Process?
The PCB fabrication process is a sequential process that involves the assembly of different layers.
The PCB silkscreen is essentially the last layer you apply during PCB construction.
You apply a PCB silkscreen on a board panel before the routing process.
Applying the PCB silkscreen at this stage allows you to a larger work surface minimizing layout errors.
Applying the silkscreen at this stage came from employing traditional screen printing which required proper alignment of the screen and panel.
Which Side Of PCB Do You Apply Silkscreen: Component Side or Solder Side?
A PCB silkscreen provides details related to the board composition, location, polarization and identification of components.
Consequently, you typically apply the PCB silkscreen on the component side.
However, you can find boards with silkscreen on the solder surface which greatly inflates the application cost.
Silkscreen on the solder side usually contains supplementary information other than component related.
What Information Does PCB Silkscreen Offer?
You find the following information provided on a PCB silkscreen:
- A variety of warning symbols.
- Indicators for part polarity.
- Test points.
- Reference designators for part location.
- Unique printed circuit board numbers.
- Manufacturer’s information such as version and logo.
What Is The Standard PCB Silkscreen Colors?
The PCB silkscreen colour needs to contrast with the solder mask colour to allow for easy readability.
Many solder masks are green in colour which when employed with white PCB silkscreen offers good contrast effect.
green silkscreen PCB
Furthermore, using white PCB silkscreen colour involves less manufacturing processes.
Even where you employ other solder mask colours such as blue, red and black, you find white PCB silkscreen favorable.
Are There Other Custom PCB Silkscreen Colors?
You can use other colours for your PCB silkscreen instead of the standard white albeit at a higher cost.
You can employ PCB silkscreen in yellow, red, black and even pink as a custom colour.
It is important when selecting your PCB silkscreen colour to ensure it offers good contrast with the PCB solder mask.
However, custom colours are typically difficult to develop in the manufacturing process.
What Is The IPC Specification For PCB Silkscreen Thickness?
The thickness of a PCB silkscreen is important as it ensures, the text or graphics does not encroach solder pads.
When this happens, the silkscreen ink melts during the soldering process into the joint thereby weakening the attachment.
The IPC specification for PCB silkscreen thickness is IPC-4781.
This specification details the “Qualification and Performance Specification of Permanent, Semi-permanent and Temporary legend and/or Marking Inks”.
The thickness of the PCB silkscreen should not be too thick as it gets blurred and difficult to read.
Alternatively, when it’s too thin it is challenging to print and can result in omissions.
How Do You Perform The PCB Silkscreen Printing?
Performing the printing of the PCB silkscreen is a delicate process that requires careful execution to achieve the desired outcome.
In PCB silkscreen printing, you find the following processes essential:
Designing Of Silkscreen
You design the silkscreen artwork by employing dedicated software such as CAD, Eagle and Altium.
You carry out the design in the program’s silkscreen option which constitutes part of the general PCB design.
Preparing The PCB
Board preparation involves selecting the appropriate board first before cleaning and taping.
You the position the design of the PCB on the silkscreen over the silk fabric to mirror the desired information.
The configuration of the board and design over the silkscreen should be perfectly aligned to ensure an accurate printing process.
Thereafter, turn the assembly such that the design is at the bottom and ensconce the top with an opaque object.
Using an UV light source, expose the design at the bottom to UV for about a quarter of an hour.
You develop the outline this way before using a stream of water to remove the emulsion exposing the silkscreen.
Printing Of The Silkscreen
Here, you mount the board onto the printing machine upon which printing takes place powered by CAD. Position the PCB under the silk fabric in alignment with the design above before securing the sides to prevent movement.
You apply photosensitive ink over the silkscreen at the configuration’s top using a squeegee to ensure the layer is even.
Thereafter, you subject the PCB to a drying oven to set the artwork by drying the ink.
Handling And Inspection
You need to carefully handle the PCB during the silkscreen printing process to prevent smudging and deterioration of the artwork.
Furthermore, inspection at every stage is tantamount to ensuring the outcome is legible and discernible.
Silkscreen treatment involves ascertaining the quality of the print process and readiness for submission upon passing inspection.
Which Are The Common PCB Silkscreen Printing Methods?
You find three common methods of printing the PCB silkscreen.
During the printing process, you find inkjet printers commonly employed in the image creation according to design layout.
Manual Screen Printing
You employ manual screen printing where you have a tolerance value of 0.005 inches with line widths exceeding 0.007 inches.
When using this method, you employ a stencil that includes the desired text and nylon traces.
Manual screen printing offers you the simplest approach to making a PCB silkscreen while allowing you to use large text.
Consequently, it is the least expensive of all the three common methods.
However, the accuracy levels of this method are fairly low and as a result requires a large component pad clearance.
You find the end-result of a PCB silkscreen made via this method less appealing compared to the other methods.
Liquid Photo Imaging (LPI)
The LPI method is similar to that of solder mask application and employed where line widths are greater than 0.004 inches.
However, you coat the laminate with epoxy before subjecting it to UV light for developing before oven baking.
You achieve higher accuracy levels than manual screen printing method with LPI with a longer setup time.
When making PCB silkscreen using LPOI, you employ white colour in much larger quantities than the other methods.
Direct Legend Printing (DLP)
DLP is the most accurate and precise method of the three used in making the PCB silkscreen of complex boards.
However, this comes at a cost as it is an expensive method and unfavorable where the boards have silver laminates.
You employ acrylic ink in this method applying on the board via CAD programme with an inkjet projector.
You simultaneously expose the ink to UV light for development.
What Are The Types Of Ink Used In PCB Silkscreen Printing Process?
When printing the PCB silkscreen, you use ink to highlight the indicators for component placement.
The type of ink you employ depends on the application process you select.
You employ two common ink types for your PCB silkscreen printing process: epoxy ink and acrylic ink.
You use epoxy ink for manual screen printing and LPI whereas you employ acrylic ink for direct legend printing.
Epoxy ink usually consists a two-part component forming a permanent ink particularly useful for making difficult markings.
Acrylic ink derives form very fine pigments when suspended in a solution of acrylic property.
Which Factors Determine The Cost Of PCB Silkscreen Ink?
The cost of applying a PCB silkscreen using a particular ink attributes to about fifteen percent of the total board cost.
However, the cost of the PCB silkscreen ink will also be influenced by several factors including:
The Text design
The text design refers to the properties of the characters in the artwork.
These include width, height, thickness, spacing and variation in placement. Using a text design with larger properties results in higher cost.
Method Of Applying Silkscreen
The method of silkscreen application influences the cost of PCB silkscreen ink.
The cost of ink depends on its adhesion properties, compatibility with substrates, immunity to alkali and acids, and curing process.
You use epoxy ink for manual screen printing and liquid photo imaging methods whereas you employ acrylic ink in DLP.
The Ink Colour
One reason most PCB silkscreens are white in colour is due to the simpler manufacturing processes involved.
Consequently, when using white ink for PCB silkscreen you undertake lower costs.
Having PCB silkscreen in other colours costs more due to the sophisticated process of developing and preparing the ink.
Single Or Double Surface Application
When applying silkscreen on both board surfaces, you require more ink.
Consequently, you incur higher PCB silkscreen ink costs compared to when applying silkscreen on only one surface.
Which Are The PCB Silkscreen Markings Employed To Accurately Mount Components?
When populating a PCB, you can lack component outlines where the components are few and regular shaped.
However, working without markings can result in misplacement of components and incorrect orientation resulting in board malfunction.
You employ the following PCB silkscreen markings to accurately mount components:
- Reference indicators: You use this market to help you identify the types of component according to the BOM.
- Pin 1 indicator: With this marking, you can determine the pin connection of a pad footprint.
- Component outline: You employ the component outline with the landing pattern to determine where you position the component.
- Polarity indicators: These indicators are useful for components requiring identification of polarities.
What Is The Recommended Font For PCB Silkscreen Layer?
PCB Silkscreen layer
When it comes to fonts for the PCB silkscreen, modern design software allow you to select from a vast pool.
However, before, you only had a few options of standard fonts applicable in PCB silkscreen design.
Ultimately, when it comes to selecting the font for your PCB silkscreen, you need to ensure it is clear and readable.
This allows other board users such as assemblers, inspectors and end users to easily identify the markings.
Which Are The Important PCB Silkscreen Guidelines To Follow When Designing Silkscreens?
When designing a PCB silkscreen, you need to follow certain guidelines to ensure you come up with a good silkscreen.
A good PCB silkscreen is readable and reliable allowing board users to easily identify the information stated and indicators.
To design a proper PCB silkscreen, the following guidelines are useful:
- You need to have similar orientations for your part numbers and component reference and polarity designators.
You can also indicate the top and bottom side making deciphering of the silkscreen easier.
- Inspect the layer for any texts that are overlapping before rotation and prior to adjusting the reference designator markings.
- Identify markings for reference designators for components positioned over circuit pads as they are useful during assembly or troubleshooting.
- Check your design for markings overlapping with via holes especially where these vias are untented.
Tented vias have covers over which you can mask and print on for marking them as test points.
- Inspect the board to ensure there are no markings which will be covered once the board is populated.
You need to move such markers to ensure they are visible when components are placed and soldered.
What Are The Important Parameters To Consider During PCB Silkscreen Printing Process?
During the PCB silkscreen printing process, you need to consider the following parameters:
You need to use an optimum font size to ensure good visibility and readability for users.
Where you employ very small font size or font with extreme widths, the graphic appears as a smudge and is unreadable.
You find the recommended font size for PCB silkscreen is a twentieth of an inch.
Where you have plenty of information with the need to fit many markings, you can use at least 0.035 inches.
An optimum line width is desirable for a PCB silkscreen since very narrow widths may print incorrectly during silk-screening.
The line width for a PCB silkscreen should go no lower than 0.006 inches.
However, you can employ wider line widths when printing larger fonts such as the company name and other trademark information.
Nonetheless, you still have to use smaller sized fonts when marking out reference designators, polarity designators and pin counts.
Spacing of PCB silkscreen away from solder pads and other board objects is necessary to prevent obscuring after population.
Additionally, having the silkscreen ink encroach the solder pads can result in defective attachment of the components during soldering.
You need to ensure the PCB silkscreen is at least 5 mils off the nearest objects and solder pads. Additionally, you need to allow a decent clearance from the board margins when printing PCB silkscreen.
While the font, line width and spacing of the PCB silkscreen is important, how you position the silkscreen items is equally important.
For instance, you need to rotate and locate reference designators and their corresponding parts close to ensure they’re readable.
It is common practice to provide two rotations of 0 and 90 degrees for your designators unless you are spatially constrained.
Consequently, you prevent repetitive rotations for deciphering every other silkscreen item.
Additionally, ensure the position of your PCB silkscreen item is such that they are not obscured by component upon assembly.
Having hidden markings makes it difficult for people such as inspectors and board technicians to identify the markings.
Which Equipment Are Used In Conventional PCB Silkscreening?
The equipment you need for applying a PCB silkscreen depends on the method of application.
There are three common methods of applying silkscreen: manual screen printing, liquid photo imaging and direct legend printing.
The manual screen printing was the conventional method, now relegated to prototypes due to technological improvements.
However, in this process, you need polyester screens and aluminium frames.
You position the polyester screen over the aluminium frame making a tight even surface. Before the imaging process you revert to emulsions wit solvent resistant properties to coat the polyester screens.
During this process, you need to ensure the screen and panel are aligned appropriately to prevent movement.
When the configuration experiments movement during the imaging process, you will get a defective artwork.
Presently, you find more use of liquid photo imaging which is considerably faster with more accurate results.
In this approach, you employ a laser plotter, UV printer, curing oven and spray developer to make the film.
You can reuse the screens in this process after cleaning from initial use. However, you note that where you need high resolutions, reuse is not an option.
What Is The Recommended PCB Silkscreen Line Width And Text Height?
Having the right PCB silkscreen size is essential since having too thick and too thin silkscreens is disadvantageous.
An excessively thick silkscreen may cause the graphics to be difficult to decipher.
Alternatively, where you have a PCB silkscreen that is too thin complicates the screen printing process resulting in omissions sometimes.
Current trends where the components are smaller with an increased circuitry makes printing the PCB silkscreen even more challenging.
When making PCB silkscreen, you need to adhere to the PCB silkscreen design rule. This rule recommends that the ratio of line width to text height is a sixth.
Furthermore, different copper weights require different width and height parameter values while still maintaining the design rule.
However, your line width should not go below 6 mils for any board weight.
How Does Line Width Affect The PCB Silkscreen Printing Process?
The line width defines the cross sectional length of a character in a PCB silkscreen marking.
The line width goes hand in hand with the text height as their ratio makes the silkscreen design rule.
The PCB silkscreen printing process intends to inform users on various aspects during assembly such as component markings and test points.
Therefore, you find the PCB silkscreen size is important as it ensures the information is clearly visible and readable.
It is recommended your PCB silkscreen’s linewidth should not exceed 6 mils.
Furthermore, the width to height ratio should be a sixth, thus for the minimum linewidth the text height is 36 mils.
The line width affects the PCB silkscreen printing process in that only an optimum width is favorable.
Where you have a line width that is too thick or too thin the process of printing PCB silkscreen is hampered.
A line width that is too thin hampers the screening process as the print outcome can have omissions.
Alternately, where you have a line width that is too thick distorts the graphics with appearance of a smear.
Should You Print PCB Silkscreen Over Solderable Surfaces?
When applying PCB silkscreen, you need to avoid solderable surfaces such as solder pads and lands.
When you print a PCB silkscreen over these surfaces, you hinder the execution of a good soldering process.
Overprinting solder lands results in the melting of the ink during the soldering process which mixes with the solder flux.
You note that this weakens the properties of solder and flux resulting in a strained attachment during assembly.
What Does Text Design Imply In PCB Silkscreen?
Text design involves the development of the PCB silkscreen graphics using CAD software such as Eagle and Altium.
During text design, you come up with the artwork you intend to print on your board surface.
You employ the design software in establishing aspects such as the line width, the text height, the clearance and arrangement.
You have different colour codes to guide your text design process such as a yellow rectangular border for the silkscreen’s outline.
Additionally, you can have a different colour for the marking’s dimensions alongside the positioning of parts and test points.
Text design PCB
How Do You Determine PCB Silkscreen Cost?
When applying PCB silkscreen, there are various factors you consider during the printing process.
These factors influence the outcome of the PCB silkscreen alongside the cost.
In determining the cost of a PCB silkscreen you consider the following:
The text design which refers to the aspects of line width, text height, thickness, spacing and variation of placement.
The text design also includes the design efforts through employing a CAD software.
The type of ink you employ in the silkscreen printing method which is either acrylic or epoxy ink.
You use acrylic ink for direct legend printing and epoxy ink for liquid photo imaging and manual screen printing.
The two inks have different properties which you can employ in your costing.
These include the adhesion property, immunity to treatment by acid-base compounds, compatibility with PCB substrate and the curing process employed.
Aside from the type and property of the ink, you can determine your PCB silkscreen cost basing on colour.
You find providing a white colour for your silkscreen is cheaper as opposed to using other colours.
Method of Silkscreen Application
You have three common methods of applying PCB silkscreen each employing specialized equipment and resources.
Manual screen printing costs much less than liquid photo imaging and direct legend printing which come at a cost.
Usually, you apply a PCB silkscreen on the component surface, however, you can also apply silkscreen on the solder surface.
Applying silkscreen on the solder surface is costly and consequently you need to factor this during cost determination.
Which PCB Silkscreen Marks Are Used For Troubleshooting And Testing?
The PCB Silkscreen allows technicians and board engineers to identify locations for conducting tests and troubleshooting.
With this markings, you can establish the functionality of a board and isolate instances of failure.
The PCB silkscreen mark you use for troubleshooting and testing are:
Test points are locations with designated values on the board surface.
Therefore, they function as indicators wherever you have a board problem as they’ll show different values from the known.
Warning symbols on the board function as indicators for areas requiring unique care or avoiding.
Such areas include board sections with high parameters such as voltage or current.
You find pat numbers useful in providing particular component information especially in the absence of datasheets for instance.
What Is The Recommended PCB Silkscreen Clearance?
You need clearance when laying out a PCB silkscreen to ensure you don’t print over the solder pads.
Overprinting the solder pads hampers solderability of the board causing problems during assembly and electrical testing.
When printing silkscreen, you need to maintain a clearance of at least 5 mils from solder pads and other board populates.
In providing the clearance you clip the marked print at the desired distance.
Which Are Some Of The Vital PCB Silkscreen Mistakes To Avoid?
Errors related to the PCB silkscreen can be destructive to the board and you have to avoid them.
Some of these errors include:
Ignoring The Polarization Markers On The Board Or Making Them Unclear
Polarization markers indicate the positive and negative terminals of components during assembly allowing you to properly align such.
Polarizing markers are especially useful for components such as electrolytic capacitors and diodes.
Your silkscreen should indicate the positive pin for the electrolytic capacitor.
For the diode, you can use the diode symbol or indicate the anode as A and the cathode as K.
Separating Solder Pads Using Silkscreen Line
When you separate solder pads using a PCB silkscreen line, you can encourage function defect on the board.
You find this error common where you have components with dual pins such as resistors and capacitors.
Here, you observe the silkscreen line cuts between the two component lands forming small solder balls during the soldering process.
These balls can find their way to the board surface and get in contact with conductive tracks causing shorts.
How Do You Mark Diode Poles On PCB Silkscreen Layer?
Diodes are special components that only conduct electric charge flow in one direction.
You find this possible due to existence of low resistance while the opposite direction experiences high resistance preventing electrical conduction.
For a diode to conduct electrical charge in a particular direction, you need to fabricate it considering the desired orientation.
Consequently, for proper board installation, you need to provide silkscreen marking identifying the positive and negative terminals.
Appropriately labelling your diodes helps you to avoid having to elucidate your board design. Additionally, you lower the chance of having an incorrect placement of diodes.
Indicating a singular positive terminal for a diode is insufficient on a PCB silkscreen due to the various diode types.
For instance, you have Zener diodes whose positive terminal could be the component’s cathode or not.
Consequently, when providing markings for diodes, you need to indicate both the anode and cathode terminals using A and K respectively.
Note the use of K for cathode instead of C eliminates confusion since you use C for labelling capacitors.
Additionally, you can highlight the orientation of the diode using the circuit symbol instead of alphabetical labels.
Using the diode symbol, however, consumes more board space and can be challenging with increased board density.
What Is The Purpose Of Clipping In PCB Silkscreening Process?
Due to an increase in the component density of boards, you find reduced space for providing informative board markings.
However, as a designer, you cannot use very small graphics for your PCB silkscreen and overprinting component lands.
It is important to provide clearances for areas such as solder lands and borders.
Where you have an overprinting of the circuit pads, you execute a clipping process automatically using the design software.
Clipping removes the overextending markings since they are a violation of the set standards and hamper board solderability.
The resulting product after clipping can be unappealing and depends on how much clipping you conduct.
You can clip the silkscreen against the subsequent solder mask, or copper layer or even the drill layer. You can avoid clipping by spacing your legend at least 8 mils from conductive pads and tracks.
When clipping, provide a clearance of at least 4 mils from solder pads.
Furthermore, you need you remove parts of the silkscreen line that are less than 4 mils.
Which Are The Common PCB Silkscreen Symbols/Reference Designators?
A PCB silkscreen gives you information related to the board that is especially useful during assembly.
A good PCB silkscreen is clear and readable reducing the chance of error during component placement.
Common PCB silkscreen symbols and reference designators you employ include:
- Component values such as those of capacitors, transistors and resistors.
- Test points that are essential during electrical board tests and troubleshooting.
- Warning symbols such as high voltage board areas requiring extra care to prevent risk of shock.
- Polarity markers you use to indicate the cathode and anode of polarized components.
- Logos and trademarks of the manufacturer.
What Is The Commonly Applied Standard For PCB Silkscreen Symbols?
There are several symbols and reference designators you employ on a PCB silkscreen.
Some of the commonly applied standard for PCB Silkscreen symbols include:
A Separate Assembly
AT Attenuator or isolator
BR Bridge rectifier
D, CR Diode (all types, including LED), thyristor
DL Delay line
DS Display, general light source, lamp, signal light
G Generator or oscillator
GN General Network
H Hardware, e.g., screws, nuts, washers
HY Circulator or directional coupler
IR Infrared Diode
JP Jumper (Link)
K Relay or contactor
L Inductor or coil or ferrite bead
LS Loudspeaker or buzzer
MP Mechanical part (including screws and fasteners)
PS Power supply
Q Transistor (all types)
RN Resistor Network
RV Varistor or Variable resistor
S Switch (all types, including buttons)
TP Test point
U Integrated circuit (IC)
V Vacuum tube
VR Voltage regulator (voltage reference), Variable resistor (potentiometer or rheostat)
Y Crystal or oscillator
In case you have any question about PCB silkscreen feel free to contact Venture Electronics team.