The specifications and requirements of PCB Silkscreen designed.

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PCB Silkscreen design mainly refers to the design of the silk layer printing on the printing circuit board (PCB). The silk layer is a special layer on the PCB, which is used to print various texts, symbols and graphics, such as circuit points, components, circuit symbols, etc. This information is mainly used for various components and functional areas on the identification, identification and management of PCB.

In the PCB Silkscreen design, many factors need to be considered, such as space restrictions, information importance and readability. Due to the limited PCB surface space, designers need to decide which information is the most critical and prefer to display this information in the silk print layer. For example, component reference signs, polar marks, pins 1 labeling, component boundary, company logo, manufacturing trademark, warning symbols, component numbers, version numbers, and date code are all common silk print content.

Design PCB Silkscreen usually uses EDA (electronic design automation) software. Designers can identify and assemble all the necessary marks, symbols and texts required for components on PCB, and then export the format that can be used by manufacturers. Modern PCB Silkscreen design usually uses a digital inkjet printer to print the screen printing image to the surface of the PCB, while the initial screen printing technology uses the screen printing method.

Importance of PCB Silkscreen

In order to lay the right background on a silkscreen PCB role, it is important that we recall the uses of a printed circuit board (PCB). PCB offers mechanical support and helps in connecting electronic components. PCBs have signal traces, conductive pathways, or copper sheet-etched traces that are laminated to a substrate (non-conductive).

The conductive tracks and components of the PCB are seen throughout the board without the right identification. This is why it is necessary for end-users and manufacturers to exist. This helps them to identify components such as:

▶Manufacturer identifiers
▶Testing points
▶Warning signs like high voltage
▶Processing types
▶Version numbers like V2, V3, etc.
▶Component orientation and numbers
▶Company logos i.e. manufacturer name

The importance and roles of silkscreen PCB include:

▶Identifying circuit points such as part interconnect, testing points, etc. quickly
▶Useful in troubleshooting circuits in case you get a defective component or a contrasting outcome
▶It helps you quickly identify components whenever you are designing or replacing evaluation requirements.
▶It serves as a form of safety by showing some warning signs, such as grounding, high voltage, etc.
▶Silkscreen PCB also helps manufacturers dung marketing and branding purposes. However, it prevents illegal duplication or forgery of circuit designs.

Silkscreen PCB is also great for evaluating products, such as rating verifications. Note that the information of your silkscreen depends on the size of your board. If your silkscreen board is a small one, make sure you take the important information seriously.

Silk print design requirements

The ratio of the word height to the word width of the silk print character is generally required ≥6: 1. There are three common font samples: where the board density is relatively large, the character of 4/25mil is commonly used (No. 1); when the conventional density is recommended, it is recommended to 5/recommended 5/ 30mil characters (No. 2); when the board is relatively loose, it is recommended to 6/45mil characters (No. 3); usually the thickness of the surface of the surface of the surface also has corresponding requirements for the width of the silk print: When the thickness of the base is 1oz, the 5/30mil character is preferred; when the base copies are 2oz, the 6/45mil character is preferred.

PCB Silkscreen requirements

1. Placement position: Generally speaking, the wire printing of resistors, capacitors, pipes and other devices should not be used in four directions when placing. This will cause debugging, maintenance, and welding.

2. Try not to hit the silk print as much as possible.

3. Do not press on the high -speed signal line (such as, clock line, etc.): For high -speed signal lines on the top or bottom layer, because this type of signal line can be regarded as a microstrip line.

4. The reading direction of the silk print should be consistent with the reading direction of the silk printing and the use direction of the chip. It is mainly because the probability of welding is reduced when welding.

5. The pins are clearly marked on the silk print.

6. Special packaging Silk Printing: For special packaging such as BGA and QFN, the size of the silk print must be exactly the same as the size of the chip.

7. Silk printing of the installation hole: The screws are added near the installation hole, and the total length and screws are marked for easy installation.

8. The two meaning of silk printing: the most commonly used RS232, many people will mark RX and TX, but there are RX and TX on the PC side. When do you use cross lines and when do you use it? Misty is unclear.

PCB Silkscreen design precautions

1. The width of the wire printing line on the board is ≥4mil, and the width of the component wire printing line is 0.

2. Silk printing and pad distance: Do not cover the welding point on the board, such as patch device pads, plug -in holes, silk printing as insulating material, once pads are put on , Mark point, etc.; usually require a 6mil spacing.  

3. Sitries between silk prints: It is acceptable to keep 6mil. There is a coincidence between the silk seal. Once the coincidence is overwhelmed, it needs to be adjusted.  

4. Silk printing direction: Silk print string arrangement should follow: the principles of string from left to right or from bottom to top when facing the right look.

5. The device bit number is placed: the device bit number should correspond to the device one by one, and cannot be reversed and transforms the order; when the density density is relatively high, you can use the method of drawing or symbolic labeling to place the bit number on the board other other boards. There is space.

6. The polar identity of the component and the “1” foot logo should be placed correctly and clearly.

7. When the labeling or symbol labeling, the added silk prints and characters added should be placed on the silk layer of Board Geometry.

The added board name number silk print is also placed on the silk seal layer of Board Geometry.  

8. The device bit number cannot be placed in the device or outside the board.  

9. When the density of the board is relatively high, when there is no space for placing the bit number, you can discuss with the customer not to sign, but you need to install pictures to facilitate the installation and inspection of the guidance device.

10. When the customer is required to write copper characters on the bottom layer, the line bronze line width: HOZ base bronze: character width above 8mil, height of 45mil or more; 1oz base bronze: more than 10mil in the character; above 50mil. At the same time, you need to do a good job of welding windows, so that the copper characters produced on the board are relatively bright.

Three Main Process Methods Of Silk Screen Printing.

The following are the most common PCB silk screen technology processes and processes on PCB:

▶Manual Silk Screen PCB: This process can be used when the line width is greater than 7mm and the registration tolerance is 5mm. For this method, you will need pcb silkscreen minimum text size and trace template made of nylon. The oil is printed onto the plate through the stencil. Next step,make the PCB board baked in a curing oven and let it to besolidification.

▶Liquid Photo Imaging (LPI): This procedure supplied greater correctness and legibility than manual screen printing. Using this method when the trace width is greater than 4 mil. Liquid photo imaging is very similar to the process of applying solder mask. In this case, a liquid photoimageable epoxy was applied to the laminate and then exposed to UV light. After that, the PCB board is developed and cured.

▶Direct Legend Printing (DLP): This is the most correct way to add PCB silk screen, but it is very high-priced. In such pcb silkscreen process, using an inkjet projector with acrylic pcb silkscreen ink, which have relevance to the original print circuit board from the CAD data. The pcb silkscreen acrylic inks is solid with UV light during printing. It should be noted that acrylic inks will not cure on boards with a silver finish.

Understand PCB Screen Printing Cost.

Due to the fixed cost characteristics, the cost of PCB screen printing is placed in the first place of non recurring tools in the PCB design process. PCB screen printing process accounts for about 15% of the total cost from PCB manufacturing cost.

1.The minimum text size design of PCB screen printing refers to the change of character width, height, PCB screen printing thickness, spacing and character position. Art fees are usually not charged separately.

2.The cost of PCB screen printing ink depends on the screen printing method used. Acrylic ink is used for the DLP method of legend printing, while other methods use epoxy ink.

3.The cost of PCB screen printing ink decided by specific features, such as curing procedure, adhesion,substrate compatibility, and immunity to acid / alkali treatment.

4.PCB screen printing color is also a decisive cost factor. The cost of white ink silkscreen is lower than that of other color inks. By optimizing the cost of PCB screen printing through the selection of PCB screen printing materials, the total cost of PCB can be reduced by about 5%.

5.The screen printing method that used also has an effect on the total cost. The cost of LPI for liquid photo imaging and DLP for direct legend printing is higher than that of manual screen printing because of the high capital cost of setup.

6.Another important factor to consider in the cost calculation of screen printing is whether you want to print legends on both sides or just on one side. In the case of both parties, the cost will rise.

Conclusion

The process of PCB silkscreen is delicate. This is because the quality of the printed circuit board can be affected. Another aspect you must consider closely is the cost aspect during the design. Furthermore, having a good understanding about the whole process of screen printing as well as the benefits and pitfalls of each of the printing methods ensures that it becomes easy to decide if you should do a DIY PCB silkscreen or consult the services of any professional manufacturer.