The inspection after PCBA cleaning is mostly performed by visual inspection. For high-reliability products, special inspection equipment and standard methods are required to measure cleanliness. The standards for measuring cleanliness mainly include ion pollution and surface insulation resistance. First, cleanliness standards (1) Ionic pollution At present, there is no clear standard for ionic contamination in [...]
Prevent the deformation of the film inside the fence. 4. Design the alignment accuracy marks on the four corners of the board. 29. Why should the board be pre-baked before registration exposure? And is it baked at low temperature (75 ± 5 ℃)? Answer: Pre-baking of the board before the registration exposure: it is to [...]
Electromagnetic oven circuit board simple maintenance method The king said, che 2019-12-02 20:56 Macao video game city waiting for you! Play and entertain Macao video game city waiting for you! Play and entertain I this mad cut god destroy demon, dozen strange can upgrade VIP I this mad cut god destroy demon, dozen strange can [...]
PCB planning mainly includes the following parts: setting the shape and physical boundary of the circuit board, setting the electrical boundary of the PCB board, and setting the installation mode of the circuit board. They are described below. 1. Set PCB shape and physical boundary In the Protel DXP PCB board file wizard, we have [...]
There are fundamental differences between components and devices, such as resistors, capacitors and inductors, which do not change the internal molecular structure in production, that is, the performance only depends on the material. Devices generally refer to semiconductors, such as diodes, transistors, etc., whose molecular structure is altered during production. For example, in the production [...]
1. Gold sinking for FPC FPC Advantages: not easy to oxidize, can be stored for a long time, the surface is smooth, suitable for welding fine gap pins and components with small solder joints, can be repeated many times over reflow welding will not reduce its weldability. Disadvantages: high cost, poor welding strength, because the [...]
Circuit board wastewater Circuit board production enterprises in the circuit board grinding, etching, electroplating, hole metallization, development, stripping process will produce circuit board wastewater. Circuit board wastewater mainly includes the following: Complexing and chelating copper-containing wastewater produced by chemical copper deposition and etching processes, with a pH value of 9~10 and a concentration of Cu2+ [...]
Trivalent iron ions react with copper in REDOX reaction to form divalent iron ions and copper ions 2FeCl3+Cu=2FeCl2+CuCl2
The electrical energy consumed by electronic devices during work, such as rf power amplifier, FPGA chip and power supply products, is mostly converted into heat emission in addition to useful work. The heat generated by the electronic equipment causes the internal temperature to rise rapidly. If the heat is not released in time, the equipment [...]
1) increase the intensity of the radiation electromagnetic field, as well as the spacing or shielding between components with more active electromagnetic induction. 2) try to avoid thick and cloudy bump voltage equipment, strong and weak signal equipment interwoven together. 3) during planning, the cut of the magnetic field line to the printed wire shall [...]