Printed circuit board manufacturing process
Manufacturing process of printed circuit boards
1. Manufacturing method of printed circuit boards
The manufacture of printed circuit board (PCB) is to transfer the printed circuit board diagram of printed circuit board to the laminated board of Shun Steel City. There are two methods of making it, that is, city formation method and addition method.
The subtraction method is also called the copper vending method, that is, the protective anticorrosive material
(1) is first applied to fill the steel foil with the substrate 1 to form the PCB pattern on the manufactured laminate and then to etch the unneeded part of the forest by chemical mechanical method. After the etching is over, the corrosion resistant layer is removed. The final step is a printed circuit made of copper foil.
The addition method, also called addition method, is the chemical deposition of copper on the insulating substrate without copper clad box. The anti-corrosion agent is used to transfer the reverse PCB plate diagram, and then the surface of the plate is cleaned and the metal layer is electroplated. At this time, the metal layer figure is the PCB board diagram. Then, the corrosion inhibitor can be removed.
At present, the commonly used method of making printed circuit board is subtraction method. According to the different methods of graphic transfer, the forming method is divided into screen leakage printing method, photographic sensitive offset printing method and graphic electroplating etching method and so on.
2. Manual fabrication of printed circuit boards
The main methods of handmade printed circuit board are tracing method, texturing etching method, copper foil pasting method and engraving method and so on. 1) tracing method
The most commonly used method for making printed circuit boards by hand is the tracing board.
1) shedding. According to the actual design size of copper clad laminate, cut the process of the baby pay attention to the board surface scratch, teach size, load shear whether there is a woolen problem. After hair and shear, use fine sand paper to form a special cleaning wave to remove the oil, rust and oxidation on the steel plate, and smooth the cards around the board to remove the hair and hair, then wash and dry with clear water to dry, wipe dry with F clean dishcloth
Extension map. Topograph is a reprinted circuit, that is, printed with paper on the coated steel sheet to print out the printed map that has been designed. In drawing, the printed wire is represented by a single line, and the suburban plate is represented by a small cluster point. It is particularly important to note that the double front plate is made with three positioning points, and this location point cannot be located in a straight line, without errors or omissions, and is then drilled in accordance with the drawing. After drawing, we should carefully check the plate of solder pad and wire. The hole must be drilled when drilling
Lead position using high speed precision table drill
Near the center and side of the plate.Too fast and too large to cause
When there is a gross margin around the clear hole
Description.
Do not stop the paper to clear,
In the absence of a system, it is not necessary to determine the shape of the traverse
Tracing is printing the heart.
When using the appropriate tone of the thin network
The silver sale of the reserved rice required for finishing shall be removed
Square corrosion layer. Tracing diagram
Vinegar, etc., can be used in colorless tracing
And please make all kinds of machine silver.
Additive 1 in liquid
Of materials such as shellac, alcohol, cortisone,
Line. Use hard guide when drawing embers
Measure methyl violet to facilitate
Wire dipped in lacquer
With soldering holes,
Observe the modification of Sichuan, trace the welding before drawing
Kefa's north view at this time, Kuo used the Tien kuenli power store
All sizes are checked as far as possible. And the paint for the traverse.
Dry graphic damage.
Have, do your best to use when you can use the workshop
I hot at both ends in case there will be no
Oil pen for existence
5) trimming.
Upon completion of tracing, inspection of pad and printing
That is, the drawing of the guidance line, whether there is a broken line or sand limit, if
Etch.
Timely repair and improvement, graphics in the
The burr or my remaining lacquer scraped off while repairing the broken thread.
Hot metal trioxide (or in proportion of 2:
When the tracing wave is fully F through,
Fully impregnate the board to a concentration of 28%-42%
Ten hydrogen peroxide at 2:1:2
In a container of hydrochloric acid + water) and stir gently back and forth
Liquid, etched to print graphics,
In the process of etching, for
At h
Speed up corrosion, brush the surface with a brush, or increase the etch
Concentration of liquid, not exceeding
Take out the board and stand side by side
The temperature of 50C is suitable for heating the liquid. All copper boxes to be installed on the plate are highly corroded
Rinse the 3min with etching water to remove the remaining corrosion solution.
Go to the paint film. After soaking in hot water, the paint film will fall off. The unremoved film can be scraped with a blade and then with a banana.
Removal of water by repeated wiping.
Repair board. Compare the etched circuit board with the schematic again, and trim the edge and welding of the printed wire with the etching knife.
The edge of the wire is neat, half smooth, and free of burrs. The pad is smooth and round and fine sandpaper is used to remove the burrs from the board. Wipe with rags.
Clean dirt, rinse with water and dry.
Apply flux. In order to facilitate welding and ensure the electrical properties of the circuit, it is necessary to apply flux and flux in the end.
It can protect the pad from oxidation and assist welding. The first thing to do is to use the rag cloth to clean the dirt.
After the completion of the cadaveric chart, when printing the drawing, the cutting tool silver f and the straight steel ruler are used to make the situation with the knife
Liu Tuo, with silver forceps F tear large do not need love copper. The micro grinding wheel can replace the knife directly on the steel foil.
Grinding out the desired graphics.
3. Manufacturing process of single-sided printed circuit board
Printing is the use of a laser printer with thickened paper to print the image of a designed printed circuit board to a hot transfer
Printed paper on a glossy surface (that is, a smooth surface). The function of transfer printing is to transfer the graphics on the heat transfer paper to the copper clad laminate. Transfer printing
The specific operation method is as follows: the printed heat transfer paper will flow on the copper clad laminate, the heat transfer machine will be pressed back and forth several times, so that
The melted toner is completely adsorbed on the copper clad laminate. After the copper clad laminate is cooled, the heat transfer paper can be removed.
One-sided board T art is simple, after making the board, there is no quality problem, but in case of million., before welding also Confucianism baby inspection t: print guide
Whether the wire and pad are clear and burr free, whether there is a bridge or break: whether the pad hole size is appropriate, whether there is a leak or not; or
Misalignment; the dimensions of the plate surface and the various processed parts on the board, especially the size of the plug part of the printed board, are accurate; whether the plate surface is accurate
Straight, no warp, etc.
4. Manufacturing process of double-sided printed circuit board
The difference between double-panel and single-sided board is that the electric circuit of double-sided printed circuit is realized by adding hole metallization I technique.
Connection. In addition, the production of photographic background and graphic electroplating etching is also a key step in the manufacture of double panels. Corresponding to different
Hole metallization process. The corresponding double panel manufacturing process there are also a variety of methods. At present, the commonly used method is to adopt
Graphic electroplating etching and SMOBC( Solder Mask Over Bare Cirouit, bare Copper coating Resistance Welding
Membrane method, here only the graphic electroplating method.
The graphic electroplating method with corrosion first and then electroplating has higher advantages. This method is especially suitable for line width and spacing.
In the manufacture of high density printed boards below 0.3mm, they are often used to produce both high precision and high density printed boards
Board. At present, most integrated circuit printed boards are produced by graphic electroplating.
1) pore metallization
On two or more layers of printed circuit boards-the connection of a sail wire is required to draw and interconnect the conductive figure of the inner layer
Signal metallization process. Hole Metallization is the key to PCB Manufacturing.Reliable method for making printed conductors for circuit boards.
Chemical deposition of copper on the surface of rear hole wall
And electroplating methods
Kong Jinhua's submission
Plating,
On the two floors, Jackie Chan
Book layer
Craft.
So that the golden hole machine sets up the required holes, however
Metallization of holes in actual production
Intersected between midcourse guidance lines
Going through.
Chemical deposition of copper electroplating copper thickening, etc. A
Pore metallization
The links are: drilling
Ask for Konneh's
Big oil one machine
Chemical cleaning liquid + shouting Wall speech
By the way, the electrical and mechanical properties are up to standard.
2) pasted photosensitive film
All metals are checked, linked with copper pin
After the hole is metallized, the bottom of the photograph should be taken)
Or light picture
Transfer of circuit graphics to overprint
On the copper sheet, in order to match the pattern rotation
In the process of moving, a layer of photosensitive adhesive clothing should be attached to the coated steel plate, that is, the road map should be kept silent.
3) production of photographic negatives
After the design of the printed circuit board is completed, the photographic negatives need to be drawn,
A negative film is usually used in the preparation of a plate, which is produced by a photographic plate making method CAD
A photographic film, which is the basis for the manufacture of printed graphics. Photographic negative
A sheet is an image that does not need to be preserved to cover with an image that is resistant to corrosion.
Light painting and printing method and other methods. Negative here
Copper foil protected by corrosion inhibitor is corroded, graphic electricity
After plating remove the corrosion inhibitor for etching, that is, the film face to see the negative image of the word.
The photographic plate making method is to take pictures of the black and white background drawing, and adjust the focal length of the camera before taking pictures.
In order to accurately achieve the design size of the printed board, the scale of the opposite proportion of the photographic base drawing for photographic negative is reduced in proportion, and the result is obtained.
To the mask used in production as specified in the design, the size of the panel shall be in accordance with the PCB. Photographic plate making
The process is basically consistent with general photography, including software tailoring. →Exposure. →→Development + fixing + washing thousands of dryness + repair board.
In order to prevent exposure of ultraviolet radiation through the film, resulting in incomplete development of the picture and text, the density of the film's transmittance is less than that of the film.
0.05, the partial density of light is more than 3. Negative film requires large contrast, no sandholes, no creases.
The method of CAD optical drawing is to use the CAD software first, and then use the PCB graphic data file to drive it.
Optical plotter,
The photographic background is drawn directly on the negative film by using light, and finally the exposure sensitive film is made by the operation of the light chamber.
Base film. The production of bottom film by CAD light drawing method has a fast speed.
, high precision and good quality
Drying, repairing boards. Etch plate anti-corrosion materials such as positive welding graphics, character marking graphics, etc., are printed through screen printing method.
Photochemistry usually begins with the first surface of the plate. Dip with a W layer of Guang Min resist and then expose the photographic negative on it. When exposed, the location of copper plate in M phase film should be accurate. Then through the development, retain the corrosion inhibitor formation of the circuit diagram, wash off the surface of the more than 1 anti-corrosion agent. Then the board was repaired to correct the adhesion, burr, and break of the pattern.
Line trachoma and other defects. The material used in repairing the plate must be corrosion-resistant.
At present, there are two kinds of photochemical methods: liquid photosensitive method and photosensitive 1 membrane method.
The liquid photosensitive method is to use the liquid photoresist to form the anti-electroplating agent. This method is suitable for the graphic transfer requirement of manufacturing high density printed circuit board. The process is as follows: pretreatment of substrate (acid treatment, brushing-+ coating drying). →Exposure development, dry etching (electroplating). →Remove the membrane.
The drying of photosensitive dry film is mainly composed of 1 film anticorrosive agent, polyester film and polyethylene film. (1) the anticorrosive agent of the film is an acid-resistant photopolymer, and the polyamide film is a substrate film with a thickness of about 30 μ m, which acts as an anticorrosion agent and a photographic film. Poly (ethylene-cautery) film is a protective layer which is covered by dry film etchant on polyester film. Its thickness is 30 ~ 40 μ m. The ten films can be divided into solvent type, whole water type, half water type and so on. The plate-making process of photosensitive dry film process includes: pretreatment (scrubbing and removing oxidizing film, oil stain, etc.)-blowing (drying-+ sticking film-+ orifice positioning-1). →Exposure-+ development. →Drying + repairing board + etching (electroplating). →Remove the membrane. The photosensitive adhesive 10 film process has the advantages of high production efficiency, simple process, high plate quality and so on.
At present, in the production of graphic electroplating, most of them adopt the photosensitive F film method and screen leakage printing method.
After the film, exposure, development, repair and other process PCB plate negative graphics have been transferred to the copper clad plate. Therefore, this "series" process is also called graphic transfer.
5) etching
Etching, also known as corrosion, is the process of using chemical or electrochemical methods to greatly remove copper foil that is not needed on a printed circuit board and to leave a simple printed circuit pattern. The commonly used etching solutions are three gasified iron, acidic or alkaline copper chloride, ammonium persulfate, complex acid, alkaline copper chloride and so on. Among them, the price of ferric chloride is low and the toxicity is low.The hot compressed air will melt the lead-tin alloy and blow the excess solder off the surface of the plate and inside the metallized hole. Finally, a bright, smooth and uniform solder coating is obtained. Hot air leveling process includes: flux-+ hot air leveling-+ cleaning, thousands of dryness, hot air leveling process in the solder temperature of 230 ~ 260C, time is 3 ~ 5s.
8) external surface treatment
The surface treatment of a printed circuit board includes coating a flux where the printed circuit board needs to be welded, printing a resistance layer on the place where the welding is not required, and printing a process such as graphics and characters where it needs to be marked. The flux is applied to improve the solderability of the board. The purpose of the flux is to improve the insulation of the board and to prevent circuit corrosion, especially on the high density lead-tin alloy board, which usually needs to be brushed in other parts other than the pad. To protect the board and improve the accuracy of welding. The flux is usually dark green or light green and can be divided into two types: heat curing and light curing.
