* General Rules

(1) When the design rules are satisfied, the production cost should be reduced as much as possible, such as: the use of 2-layer boards should be used as much as possible; when the cost and design rules conflict, the design rules should be guaranteed.

(2) Components are arranged neatly, the same chips are arranged in rows and columns according to certain rules; the spacing between components should consider the production process and cannot affect the welding.

(3) For PCB design, you cannot use automatic routing for design.

* Detail Rules

(1) Use of wiring layer

When designing circuit boards with more than two layers, the use of internal electrical layers is prohibited. Use the inner layer definitions as normal layers.

For unit boards that require blind-hole and buried-hole design, for four-layer boards, punch holes 1-2,3-4,1-4; for six-layer boards, punch holes 1-2,2-5,5-6; specific The process must be confirmed with the PCB manufacturer.

(2) Separate power supply for digital device and driver device

The digital ground and analog ground must be separated and wired. The power of the digital part is connected to the power of the drive part only through the jumper at the entrance of the power base.

When there is space on the board, it is recommended to separate the power supply for the column drive and the power supply for the row drive.

(3) Power line and line:

The power line width of the digital part is> = 50mil.

The width of power lines and line lines should take into account the current, width, and distance of the power supply branches.

Ensure that the voltage drop from the power inlet to the module is not greater than 0.01V.

It is recommended to place the power supply base in the middle of the board.

When the power supply base is placed to one side, reserve the power supply base or pads on the symmetrical side to facilitate flying leads during production.

When wiring is difficult, reserve power pads on the board to facilitate flying leads during production.

There should be a separate power socket or pad on the circuit board where the limp drive is located.

There should be a separate power socket or pad on the circuit board where the inline driver is located.

When using non-welding method (pin, row and cable) for power and line connection, the current of each pin is not more than 1A, and at least two pins are connected to each.

Separate discussions for users who have existing light boards.It is recommended to place the line tube within 1/3 of the entire unit board floor in the middle of the line.

For outdoor screens, if the lamp board drive board is separated, the line tube should be placed closest to the line lead pins.

(4) Requirements for ground wire

The ground line width of the digital part is> = 50mil.
The ground wire of the queue drive part should be wider than the power line of the row drive. It is recommended to be 1.5 times the width of the power line.
The ground line of the unit board should be arranged in a checkerboard shape, and the branches should communicate with each other.
The driving part is paved with copper, and the digital part is paved with grid. The distance between the ground and other parts is set to 20mil or more. The grid ground has a line width of 25mil and a center-to-center spacing of 40mil.
When paving the ground, avoid dead spots without loops. After the grounding is completed, the parts of the divided ground are connected by manual grounding.
Put the test ground pin at the power inlet of the analog ground.
Digitally place a test ground pin between the input pin, output pin, and 9702.

(5) Capacitor requirements

Put 100u electrolytic capacitors and 104 capacitors in the power inlet of the driver and digital parts.
Put a 100u electrolytic capacitor at the entrance and end of the power cord branch.
It is recommended to leave a 100u electrolytic capacitor near the line driver chip.
The position where 104 capacitors are left between the power pin and the ground of the driving chip.
(6) Chip power pin out
Serial-to-parallel chips, the power pin out of the row driver chip is at least as wide as the pin pad.(7) Column and signal lines:
The width of the light panel, column line and signal line of the outdoor screen> = 12mil. When the PCB size is large, the recommended signal line width is 15mil.
For other occasions, the width of the column and signal lines is recommended to be 12mil, at least 10mil.
Line spacing is not less than the minimum line width.
(8) Via:
The outdoor panel light board, the via parameter is 50 mil, 28 mil.
For other occasions, the recommended via parameters are 50 mil and 28 mil. At least 40 mil, 24mil.The distance between vias and lines is not less than the minimum line width.
Outer diameter of power mains vias << / span> Power line width, inner diameter of mains vias> = Power line width * 1/3 Recommended via diameter: 28mil, 40mil.
Large power and ground leads can increase the number of vias.
To ensure soldering, do not place vias on the pads. At least 5mil from the pad.
(9) Insert welding device pad:
The through holes of the solder pads of the device should be ensured that there is no problem in device connection.
Inner diameter of ordinary pinhole is 40mil, and the power supply pad hole is 60mil.

(10) mounting holes:

For unit boards using LED modules, the mounting holes must not be located at the junction of the two modules. There must be no copper foil around the holes to prevent the mounting holes from being connected to the DC ground of the unit board. ).
General components should be placed at a distance of 3.5mm away from the center of the fixing hole, and higher components (such as capacitors, plug-in chips) should be placed at a distance of 5mm or more from the center of the fixing hole.
When the user does not have a clear requirement, the cascade header and the power socket must be placed 2cm away from each of the horizontal and vertical lines of the fixing hole.
When designing a PCB for a specific customer, the customer’s fixing hole location and fixing structure must be clear to determine the placement of pin headers, power sockets and other components.

(11) Module

Do not insert soldered components at the module boundary.
Modules are recommended to be placed in “queue” or grid mode to avoid errors.
The PCB edge should be at least 20mil smaller than the module.
The module is built according to the front view, and it is positioned on the back when placed, so that the front pads of other devices can be prevented from being covered by the silk screen at the module boundary.
The center distance of module placement should be the dot distance * 8. When the accuracy of the module is too low to guarantee the data, the center distance of the module placement with the customer should be implemented.

(12) Optimization:

After the layout design is completed, it should be reviewed to optimize the routing.
The width of the power cord should be increased, and the ground wire should be arranged in a checkerboard shape as much as possible.

(13) Layout order: pre-layout before layout, adjust the alignment of column lines, you can return to modify the schematic diagram and netlist to make column line routing the most convenient. When laying the board, you must route the wires, power and ground wires, cascade signal wires, and then other wires.

(14) After the PCB design is completed, there should be a description of the PCB processing process requirements for the unit board, including: PCB board thickness requirements, PCB board copper foil thickness requirements, PCB board minimum line width, PCB board minimum spacing, and PCB minimum via parameters. Convenient to choose the board manufacturer during the board investment process.

(15) After the PCB design is completed, a component list should be prepared, and various component packages should be clearly marked. If there is a reserved place and components that do not need to be soldered during production, it should be specially indicated. The component list should also include simple soldering notes.

(16) silk screen layer

After the design of the unit board is completed, the unit board information is marked on the TOP layer of the unit board, including the board number, the basic parameters of the unit board, and the completion date.
The unit board should have obvious cascade direction signs at the prominent positions of the cascade inlet and the cascade outlet; there should be obvious signs at the 1-pin position of the cascade header and other headers; There should be an easy-to-see + sign beside the pin, and there should be a clear indication of the soldering direction. For empty pads designed for jumpers, an obvious network name logo should be placed. For unit boards where the lamp board and the driver board are separated There should be a clear indication of the direction of the plug on the light board and the driver board, or asymmetric processing should be done during the design.For components with positive and negative electrodes, the direction of the positive and negative electrodes must be reflected on the layout. Such as diodes, voltage regulators, electrolytic capacitors, power sockets, etc., and the direction of placement cannot be covered after welding is completed;
For the unit board of virtual pixels, in addition to the welding direction of the LED, there must be a clear R / G / B mark. For the unit board that cannot be used for surface silk-screen LED lamps, it must be described in detail in the production instructions. Of permutations.

In order not to affect the soldering, the characters of the silk screen layer should not overlap the pads.
After the drawing is completed, place the name of the IC under the IC; for 62706 or 595, place the color control logo next to the IC;
After the PCB design is completed, place the optical positioning points on the diagonal of the PCB.

(17) Detection

DRC testing is required after the design is completed. When using PROTEL99 and POWERPCB to make a map and then switch to PROTEL2.8, DRC testing is also required.
After drawing with PowerPCB software, when importing to Protel2.8 format, it should be noted that sometimes the vias on the board will change size. After drawing with Protel99 software and importing to Protel2.8 format, the vertical placement of FILL may be changed to horizontal placement. These are things that need attention in drawing.
When drawing the PCB, for the components that divide the positive and negative electrodes, it must be able to reflect the direction of the positive and negative electrodes on the layout. Such as diodes, voltage regulators, electrolytic capacitors, power sockets, etc.
For two-pin components, the library of ordinary two-pin components of SIP2 or IDC2 must no longer be used, and a dedicated component library must be used.
For the power socket or power pad, the network name (or the positive and negative signs) must be marked on the silk screen.
For single-row and double-row pins, the position of one foot must be clearly marked.
For other components, be sure to have a 1-pin mark or welding direction mark.
For unconventional usage, be sure to explain in the production instructions.
For the unit board of virtual pixels, in addition to the welding direction of the LED, there must be a clear R / G / B mark. For the unit board that is surface-mounted and cannot be printed on the bottom layer, it should be explained in detail in the production instructions.