Printed circuit board
Print the printed circuit board with transfer paper, paying attention to the slippery side facing you. Generally, two circuit boards are printed, that is, two circuit boards are printed on one sheet of paper. Select the best printed circuit board among them.
Cut copper laminate
The whole process of making a circuit board with a photosensitive plate. Copper-clad board, that is, a circuit board with copper films on both sides, cut the copper-clad board to the size of a circuit board, not to be too large, to save material.
Pre-treated copper clad laminate
Use fine sandpaper to polish off the oxide layer on the surface of the copper-clad laminate to ensure that the toner on the thermal transfer paper can be firmly printed on the copper-clad laminate when the circuit board is transferred. Stains.
Transfer circuit board
The printed circuit board is cut to a suitable size, and the printed circuit board is pasted on the copper-clad board. After being aligned, the copper-clad board is placed in a heat transfer machine, and it must be ensured that the transfer paper is not misaligned. Generally, after 2-3 transfers, the circuit board can be transferred to the copper-clad board very firmly. The heat transfer machine has been preheated in advance, and the temperature is set at 160-200 degrees Celsius. Due to the high temperature, pay attention to safety during operation!
Corrosion circuit board
First check whether the circuit board is completely transferred. If there are a few areas that are not well transferred, you can repair them with a black oil-based pen. Then it can be corroded. When the exposed copper film on the circuit board is completely corroded, remove the circuit board from the corrosive solution and clean it, so that a circuit board is corroded. The composition of the corrosive solution is concentrated hydrochloric acid, concentrated hydrogen peroxide, and water. The ratio is 1: 2: 3. When preparing the corrosive solution, release the water first, and then add concentrated hydrochloric acid and concentrated hydrogen peroxide. Be careful to splash the skin or clothing with clean water in time. Because of the use of strong corrosive solutions, please pay attention to safety during operation!
PCB drilling
The circuit board is to insert electronic components, so it is necessary to drill the circuit board. Select different drill pins according to the thickness of the pin of the electronic component. When using a drill to drill holes, the circuit board must be pressed stably, and the speed of the drill cannot be opened too slowly. Please watch the operator carefully.
Circuit board pretreatment
After drilling, use a fine sandpaper to polish the toner covering the circuit board, and clean the circuit board with water. After the water is dried, apply rosin to the circuit side. In order to speed up the rosin''s solidification, we use a hot air heater to heat the circuit board. It takes only 2-3 minutes for the rosin to solidify.
Layout design
The matters needing attention in layout design are explained in detail as follows:
Single panel
This type of panel is usually used when the cost requirements are low. In layout design, sometimes components or jumpers are needed to skip the board''s traces. If there are too many, you should consider using a dual panel.
Double panel
Dual panels can be used with or without PTH. Because PTH boards are expensive, they are only used when the complexity and density of the circuit are needed. In layout design, the number of wires on the component side must be kept to a minimum to ensure that the required materials are easily available. In PTH boards, plated through holes are used only for electrical connections and not for component mounting. For economic and reliability reasons, the number of holes should be kept to a minimum. To choose single or dual panel, it is important to consider the surface area (C) of the component, which is an appropriate constant ratio to the total area (S) of the printed circuit board. The installation is useful. It is worth noting that "US" usually refers to the area of one side of the panel. Table 3-2 lists the range of S: C ratios for the most commonly used printed circuit boards.
