To design the general procedure of printed circuit board.
In the design of circuit board, the first response to the electronic production of all components of the pin size, structure, sealing form with real Numbers in detail, which should be paid attention to are sometimes the same types of components for manufacturers in different numerical and pin is arranged on the differences; Secondly, according to the electrical schematic diagram designed, the overall block diagram of the components is simulated: finally, the sketch of the circuit board is drawn according to the block diagram and the electrical requirements. Detailed pin in each element and its position in the circuit boards, components should be handled well in the size and the distance between each other, peripheral components from the edge of the size, input, output, earthing and power cord, high frequency circuit, easy to radiation, easy to interference signal, etc.
Printed circuit board design principles.
1. Component layout
First, consider the PCB size. When PCB is too large, the printing line is long, the impedance is increased, the anti-noise ability is decreased, and the cost is increased. Too small, the heat dissipation is not good, and the adjacent lines are easily disturbed. After determining the PCB size, understand the properties information of each component, including electrical performance, contour size, pin distance, etc., and then determine the location of the components. Finally, according to the functional unit of the circuit, the layout of all components of the circuit needs to be paid attention to:
1) the arrangement of the components is usually directed to the signal, starting at the input level and terminating at the output level. Each unit circuit is relatively concentrated and centered around the core device, which is arranged around it. To minimize the connection between high frequency components, reduce their distribution parameters and electromagnetic interference between them. For adjustable element layout, it is convenient to adjust. Vulnerable components cannot get too close to each other, and input and output components should be kept away from each other.
2) symmetrical circuit, such as push-pull amplifier, differential amplifier, bridge circuit, etc., should pay attention to the symmetry of components. As far as possible, the distribution parameters should be consistent. The coil with iron core should be placed vertically and away from each other, so as to reduce the coupling between each other.
3) the layout of adjustable elements such as potentiometer, adjustable inductor coil, variable capacitor and micro switch should be considered as the structure of the whole machine. If the adjustment in the machine, should be placed in the printing plate to facilitate the adjustment of the place; In case of external adjustment, the position should be adjusted to the position of the adjusting knob on the cabinet panel.
4) the components are evenly arranged, compact and compact, and the density is the same. Try to be horizontal and vertical, so that the components can not be sloped or crossed. The lead between the unit circuits should be as short as possible and the number of leads as few as possible.
5) the component on the edge of the circuit board is not less than 2mm from the edge of the circuit board. The distance between the shell of each element shall be determined according to the voltage between them and shall not be less than 0.5mm.
2, wiring,
After the layout of the components is determined, the wiring should be started and the following points should be noted when printed circuit board wiring:
1) wiring is shorter, especially the transistor's base, high frequency, high and low potential difference is bigger, lead and adjacent lead, should be as short as possible, try to large spacing and turn round, input and output side with adjacent parallel wires should be avoided. 2) - the common ground line is arranged on the edge, so that the printed circuit board can be arranged on the chassis.
3) the printed wiring that should not be connected on the same layer of printed circuit board shall not be crossed. The minimum width of the printed conductor is determined by the adhesion between the wire and the insulating substrate and through their current value. Wire width of 1.5mm can meet the requirements. For the integrated circuit, especially the digital circuit, usually choose 0.02~0.3mm wire width.
4) the curved section of the printed wire is usually rounded, while the right Angle or Angle will affect the electrical performance in the high frequency circuit. In addition, avoid the use of large area copper foil, otherwise, long time heating, easy to happen copper foil expansion and shedding phenomenon. When you have to use a large area of copper foil, it is best to use a grid. This is beneficial to exclude the volatile gas produced by the heat between copper foil and substrate.
3, welding plate
The center hole of the welding disc is slightly larger than the diameter of the device lead. Welding disc is too large and easy to form virtual welding. The outer diameter of the welding disc is not less than (D +1.2) mm, where D is the lead aperture. For high density digital circuit, the minimum diameter of the welding disc is desirable (d+l.O) mm.
Simple DIY printed circuit board design and production process.
Assembly of printed circuit boards.
1. Component lead forming.
In order to make the components orderly and beautiful on the printed circuit board, it is also an important step to avoid virtual welding. Usually with pointed nose pliers or tweezers. There are many kinds of components, such as basic forming method, bending molding method, vertical interpolation molding method, integrated circuit forming method, etc.
2. Pretreatment of components lead wire and wire end welding.
In order to ensure the quality of welding, the impurities on the lead wire must be removed before welding, and the tin shall be treated with the tin. Truncation conductor, wire with insulation layer according to the required length by wire connection decided to strip and strip head, head length multi-strand wire twisting head processing and tin, which can guarantee medium access circuit after assembling can be conductive lead good and able to bear certain pulling force without break.
3. Instrumentation of components.
There are two methods for the axial symmetry element, such as resistor, capacitor and semiconductor device, which is related to the design of the circuit board and the specific requirements. Components after instrumentation to the circuit boards, after the lead through the solder should retain a certain length, l - 2 mm or so commonly, upright style, don't bend after pin through the bonding pad, desoldering convenient, half bending type pin bent into 45 degrees, has certain mechanical strength, the bending type, pin bent into a 90 degrees or so, has high mechanical strength, to pay attention to the direction of welding plate wire bending.
4. Welding of components.
In welding circuit, the printed circuit board is divided according to the unit circuit, generally starting from the signal input end, in turn welding, first welding the small element, then the large element. When the welding resistance, make the discretion of the resistor is consistent, capacitance should pay attention to "+", "one" can't wrong polarity, the diode can't wrong polarity of Yin and Yang, triode in welding when the welding time as short as possible, use tweezers to clamp the lead foot, for heat dissipation. Integrated route of electric welding diagonal two pins, and then from left to right, from top to bottom by welding, welding, welding head can stick a tin content in weld 2-3 pins only advisable, soldering iron head contacts the copper foil on the printed circuit board, solder entered at the bottom of the IC pins, welding head to contact pins, contact should not be more than 3 s, and to make soldering evenly cover the pins, to check whether leakage after welding, touch welding, welding, welding and solder joints.
5. Welding quality inspection.
1) visual inspection
Visually check whether the welding quality is unqualified, whether leakage welding, solder joint around the residual flux, with and without welding, bridge welding, welding plate crack, whether smooth, solder joint for the icicles, etc.
2) manual inspection
Touch components, loose, the phenomenon of welding rickety, pull gently with forceps between live components lead, have loose phenomenon, solder joints when shaking, the solder have falls off phenomenon.
Simple DIY printed circuit board design and production process.
DIY printed circuit board design and production process.
Tools/materials:
The photosensitive circuit board x1 block.
It is an x1 bottle of iron chloride, or an environmental etching agent x1.
The photographic plate developer x1.
Transparent glue x1 roll.
Low pencil x1
Low lamp x1
(the thicker the better) x1.
A plastic tub or a fresh box x1 (note that it must be plastic!! )
The Smith knife x1
Low steel rule x1
(unless you want to run out of all the drugs at once)
A stopwatch, a watch, a clock.
The flat head tweezers x1.
Electric drill, bench drill, can punch holes. Pay attention to using a thin bit! About 0.8mm is appropriate.
Production steps:
1. Draw and print circuit diagram.
First of all, I will draw the circuit diagram. Here I use a PCB design software called SprintLayout to recommend SprintLayout to your friends. It is easy to operate because of easy operation.
The SprintLayout needs to be printed. Don't have the printer to baidu check "virtual printer SmartRrinter cracked versions", this is a very practical green software, you can put any documents - so long as has the print options, converted to N format images, then take the pictures to the printing shop to print, it's a way to save with a. LAY the file to print, the somebody else again dozen don't open of stopping condition...
Print out the circuit diagram! Cut it down according to the size of the design! It should be noted that if you look carefully at the lines you printed, there will be broken lines or short circuits... Any defect, the plate will follow you. So if it is an inkjet printer, please loosen the line a bit. If the line is broken, it will be filled up.
Simple DIY printed circuit board design and production process.
Simple DIY printed circuit board design and production process.
2. Start to sensitize
In the middle is the old plate of the gold electron (which has expired TwT), and on the left is a new version of the plate. On the far right is trichloride, one bottle. Here is the plate developer.
Many people ask about the price of the plate. In guangzhou, where I live, there is a new saige electronic city, and there is one on the third floor, which can buy 100&TImes. 150mm big board, that's enough. Bottled trichloride for a dozen yuan, can corrode N multi - circuit board. Imaging agent, $1 thing...
Cut the circuit diagram. Note: the light sensitive plate is sensitive to light, and the lamp is turned off. Use a knife and steel ruler to draw out the area you need on the plate. Arrange the circuit board according to the picture, then press down with the other hand! Cut it out!
Cut it again. Cut it. Be careful to tear off the white protective film! Do the photosensitive work again! After tearing off the film, you should see the dark green photosensitive layer. Apply transparent tape to the sensitive film on the side of the road map.
The photographic film is facing up and is pressed with glass. I got the glass from someone else's house... The thicker the better, the thicker, the heavier, the pressure is tight. Control the distance between the lamp and the board at about 5CM!
All right, light up! Be careful not to touch the glass during the photosensitive process. Do not turn off the lamp or move the lamp. Turn off the lamp after 20 minutes or so!
Simple DIY printed circuit board design and production process.
Simple DIY printed circuit board design and production process.
3. Configure the developer.
In the clearance of light, let's configure the developer. A pack of imaging agents is 29G, and about 10G is enough. According to the developer: water as a ratio of 1:20 to prepare the developer solution (again emphasize the use of plastic basin!). Pour the developer into the prepared 200ML water, stirring, shaking the container until the developer is completely dissolved and no longer any particles. Then take out the printed circuit board, tear out the transparent glue, and it should be like this.
Will the board slowly into developer (don't throw into it), after a few seconds, can see the circuit part of the photographic film gradually into the green mist and floating out, gently shaking plastic containers at this time, until the situation as shown in the figure below. The part of the line is clear, and the ink on the non-line part should be dissolved. Wait for another 3-5 seconds. To ensure that the imaging process is 100% complete!
Note: the used image liquid is strictly prohibited to be used again. The used imaging solution will be diluted 20 times before discharging into the city water system!
Simple DIY printed circuit board design and production process.
Start etching.
Weigh the appropriate amount of iron chloride, and then press three ferric chloride: the water is about 3 to 1, and the etching solution is configured.
It must be noted that ferric chloride is corrosive, and it is strictly prohibited to use hand to grab, and the tweezers should be cleaned after use. If you accidentally enter your eyes, please rinse immediately with plenty of water and find a doctor as soon as possible! Then throw the iron trichloride into the water, and in a few minutes you'll see, it's very slow to dissolve...
When the solution is brown and does not have any solid, it means that the etch has been configured!
Note: make sure there is no impurities in the etching solution! The most intolerable impurities in etching are grease! A few nails in the water can speed up etching. Try it?
Slowly put the plate in the etching solution. (actually, the circuit should float down on the surface of the liquid. However, due to the insufficient area of the board, only the bottom... ) don't touch the plate in the process, and don't touch the board with anything! Otherwise the consequences will be serious!
Look in an hour. Increase the concentration of etching solution! In this case, you can use plastic bags as gloves and carefully take out the board (don't touch the line part!) Is there no metallic color in the non-line part? If there is continue to soak for half an hour to see again ~ if not sure, can use multimeter test as shown in the figure below part not circuit resistance, resistance if infinity! If you measure it this way, congratulations, your first photosensitive circuit board has been made.
Simple DIY printed circuit board design and production process.
5. Drilling, installing components and welding.
Bench drill hole! Be careful not to be biased, dense holes, it is better to clean up the dregs from the holes... The highlight is the addition of the complementary optical system (6 3MMLED), enhancing the stability of the structure. Installation components, welding! Put 20 "straw hat leds" in place.
Simple DIY printed circuit board design and production process.
6. So far your first beautiful printed circuit board has been made.