Технические характеристики процесса проектирования печатных платОпубликовано 2019-12-06
Determining PCB board material and dielectric constant
Commonly used PCB materials are: FR-4, aluminum substrate, ceramic substrate, paper core board, cardboard with cloth, phenolic resin board, etc.
Our company’s products: FR-4 is mainly used for double panels; aluminum substrate is mainly used for single panels; but the power board must use flame-retardant cardboard with cloth; multilayer boards are determined according to design.
Dielectric constant. When печатной платы with RF signal is to be specified, its parameter value should be specified. Now we generally choose 4.800 grade dielectric constant.
What are the печатной платы requirements
What are the печатная плата thermal design requirements
печатной платы device library selection requirements
What are the basic layout requirements of the PCB board
печатной платы routing requirements；
PCB board fixing holes, mounting holes, vias requirements；
What is required for the reference point (MARK point) of the PCB board；
What are the requirements for PCB screen printing；
PCB board safety requirements are？
PCB board size and appearance requirements
Determine the surface finish of the PCB;Such as: tin-plated, nickel-plated gold, anti-oxidation, etc., and noted in the document.Determine the thickness of the печатной платы
Without special requirements, try to use a plate with a thickness of 1.0mm or more.Determine the copper foil thickness of the PCB;Considering the overall quality of the PCB, the thickness of the copper foil is at least 35um.
What are the PCB thermal design requirements
High heat devices should be placed in the air outlet or in a position conducive to convection;Higher components should be considered at the air outlet and do not block the air path;The placement of the radiator should be considered to facilitate convection;The edge of the heat sink must be at least 3mm.Temperature sensitive devices / pieces should be considered away from heat sources
For heat sources whose temperature rises above 30 ° C, general requirements:.
Under air-cooled conditions, the distance between the temperature-sensitive devices such as electrolytic capacitors and the heat source must be greater than or equal to 2.5mm;
Under natural cold conditions, the distance between the temperature sensitive devices such as electrolytic capacitors and the heat source must be greater than or equal to 4.0mm;
If the required distance cannot be reached, a temperature test is required to ensure that the temperature rise of the temperature sensitive device is within the derating range.
Thermal resymmetry of pads at both ends of chip components under 0805 and below 0805 through reflow
In order to avoid the phenomenon of deviation and monument after the device is reflowed, the pads at both ends of chip components 0805 and below 0805 that are reflowed should ensure heat dissipation symmetry, and the width of the connection between the pad and the printed wire should not be greater than 0.3 mm (for asymmetric pads), as shown below
How to install high-temperature devices and whether to consider a radiator;The installation of high-temperature devices should be easy to operate and solder;When the heating density of the device exceeds 0.4W / cm3, the unit needs sufficient heat dissipation due to insufficient device pins and body.Measures such as a heat sink and bus bars should be used to improve the overheating capacity.
PCB component package inventory of new devices should be determined
Devices not included in the печатной платы component package library
1. Establish the package according to the device information, and add the PCB component package library;
2. The new device package must ensure that the silk screen matches the physical object, and the size of the frame and the physical object shall prevail;
3. The details of the newly packaged device package must be clearly marked, especially the electromagnetic components and self-made structural components, which must be consistent with the component information (recognition, drawings);
4. The new device package must meet the requirements of different processes (reflow soldering, wave soldering, and through-hole reflow soldering).