Seektronics

1.  PCB board surface treatment   PCB board surface treatment processes include: anti-oxidation, spray tin, lead-free spray tin, sink gold, sink tin, sink silver, hard gold plating, full-board gold plating, gold finger, nickel-palladium-gold OSP, etc.. Requirements are mainly: lower cost, good solderability, harsh storage conditions, short time, environmentally friendly processes, good welding, flat . Tin spraying: Tin spraying boards are generally multi-layer (4-46 layers) high precision PCB prototype boards, which have been used by many large domestic communication, computer, medical equipment and aerospace companies and research units.   The connecting finger is the component on the memory stick that connects to the memory slot, and all signals are transmitted through the gold finger. Gold fingers are composed of numerous gold-colored conductive contacts, which are called "gold fingers" because of their gold-plated surface and the finger-like arrangement of the conductive

PCB engineers in doing PCB design, often encounter a variety of safety spacing problems, usually these spacing requirements are divided into two categories, one is the electrical safety spacing, the other is: non-electrical safety spacing. So, what are the spacing requirements for designing PCB circuit boards?   First, the electrical safety spacing   1 the spacing between the wires: the minimum line spacing, also line-to-line, line-to-pad spacing shall not be less than 4 MIL. from the production point of view, the greater the better, of course, when available. The general routine 10MIL is more common.   2 pad aperture and pad width: according to PCB manufacturers, pad aperture if the mechanical drilling method, the minimum shall not be less than 0.2mm; if the laser drilling method, the minimum shall not be less than 4mil. and aperture tolerance according to different plates slightly different, generally can be controlled within 0.05mm; pad width of the minimum shall not be less than 0.

  Protel 99 SE provides 32 signal layers, including the Top layer, Bottom layer and 30  M iddle layer.   Top signal layer: also known as the component layer, mainly used to place components, for multilayer boards can be used for wiring.   Mid Signal Layer: up to 30 layers, used to lay signal lines in multilayer boards.   The bottom signal layer : also known as the solder layer, mainly used for wiring and soldering, and sometimes can also be placed on the components.   Silkscreen layer: The silkscreen layer is mainly used for placing printed information, such as component outline and labeling, various comment characters, etc. Protel 99 SE provides two silkscreen layers, Top Overlay and Bottom Overlay. Generally, various annotation characters are placed on the top screen printing layer, and the bottom screen printing layer can be closed.   Top silkscreen layer: used to mark the projected outline of the component, the component's mark, nominal value or model number and various comment

Via in pad   as the name implies, is to hit the hole in the pad, with the increasing integration of electronic products, the components package is getting smaller and smaller, especially in complex PCB design pin spacing is too small, not hit the plate in the hole can not fan out, then you must hit the plate in the hole, from the next layer out of the line.   In the drawing of the PCB, the plate in the hole is nothing special, is over the hole in the pad, but there are several types of PCB production and processing processes, as hardware engineers must understand.   The most common hole in the plate   Is the hole in the pad, the production of PCB does not require a special process, the pad will leave a "hole eye", if the hole eye is too large may cause tin leakage problems, may also lead to false soldering problems, this process is the cheapest and most common, as follows QFN package on the heat sink hole.   Resin plugging hole + copper plating cap   This type of plate-in-the

  A good circuit board, in addition to achieving the principle function of the circuit, but also considers EMI, EMC, ESD (electrostatic discharge), signal integrity and other electrical characteristics, but also to consider the mechanical structure, the heat dissipation of large power consumption chips, on this basis and then consider the aesthetic issues of the board, just like the art of carving, deliberate on every detail of it.   Common PCB layout constraints principles   In the layout of PCB components often have the following considerations.   (1) Does the PCB board shape match the whole machine?   (2) Is the spacing between components reasonable? Are there any horizontal or height conflicts?   (3) whether the PCB needs to be put together? Is the process edge reserved? Are the mounting holes reserved? How to arrange the positioning holes?   (4) How to place the power module and heat dissipation?   (5) Is it convenient to replace the components that need to be replaced frequently?