Manufacturing process of PCB 2021-10-11

commonly pcb What are the board making processes ？

• Pcb Production is generally divided into ：PCB Layout → Making of core board → Inner layer PCB Layout transfer → Core plate drilling and inspection → Lamination → drill hole → Chemical precipitation of copper on the pore wall → Outer layer PCB Layout transfer → Computer control and copper electroplating . The specific operation process is as follows ：

01 PCB Layout （Layout）

• PCB The manufacturer receives from the customer CAD After the document , Because of every CAD Software has its own unique file format , therefore PCB Manufacturers usually send customers CAD File into a unified format ——Extended Gerber RS-274X perhaps Gerber X2. After that, the Engineer shall check PCB Whether the layout conforms to the manufacturing process , Whether there are defects .

02  Making of core board

• Clean the CCL , Prevent the final short circuit or open circuit of the circuit due to dust .
• The picture below is a 8 layer PCB Legend , It's actually made up of 3 Copper clad sheet （ Core plate ） Add 2 Zhang Tongmo , And then it's bound up with a semi-cured sheet . The manufacturing sequence is from the middle core plate （4、5 Floor line ） Start , Keep piling up , Then fix .4 layer PCB The production is similar , It's just 1 Add... To the core plate 2 Zhang Tongmo .

03  Inner layer PCB Layout transfer

• First you have to make the center core （Core） Two layers of lines . After the copper clad plate is cleaned, a photosensitive film will be covered on the surface . This film will cure when exposed to light , A protective film is formed on the copper foil of the copper clad plate . Two layers PCB Layout film and double-layer copper clad plate , Finally, insert the top PCB Layout film , Make sure you have two floors up and down PCB The layout of film lamination is accurate
• It's for the photosensitizer UV The lamp irradiates the sensitive film on the copper foil , Under transparent film , The film is cured , There is still no cured photosensitive film under the opaque film . The copper foil under the curing film is needed PCB Layout lines , Then wash out the uncured photosensitive film with alkali solution , The required copper wire will be covered by a cured photosensitive film . Then use strong alkali , such as NaOH Etch away unwanted copper foil . Tear off the cured film , Show what you need PCB Lay out the circuit copper foil .

04  Core plate drilling and inspection

• After the core board is successfully manufactured, make alignment holes on the core board , It is convenient to align with other materials .
• Once the core board and other layers PCB When pressed together, it can't be modified , So inspection is very important . Automatically and by the machine PCB Compare the layout drawings , Error checking . So the first two layers PCB The board has been made .

05  Lamination

• Here we need a new material called semi curing sheet （Prepreg）, It's the core and the core （PCB The layer number >4）, And the adhesive between the core plate and the outer copper foil , It also serves as insulation .
• The lower layer of copper foil and two layers of semi-cured sheet have been fixed in advance through the alignment hole and the lower layer of iron plate , Then put the core plate into the alignment hole , Finally, two layers of semi-cured tablets are successively placed 、 A layer of copper foil and a layer of pressure bearing aluminum plate are covered on the core plate . Will be caught in the iron plate PCB The boards are placed on the supports , Then it is sent to the vacuum hot press for lamination . The high temperature in the vacuum hot press can melt the epoxy resin in the semi curing sheet , Fix the core plates and copper foils together under pressure .
• After lamination , Remove the press PCB The upper iron plate of . Then take away the aluminum plate under pressure , Aluminum plate also plays a different role in isolation PCB And guarantee PCB The outer layer of copper foil is smooth . It came out at this time PCB Both sides will be covered with a smooth layer of copper foil

06  drill hole

• First of all, we need to drill through the holes PCB, And then metallize the wall of the hole to conduct electricity .
• Put a layer of aluminum plate on the punching machine , And then PCB Put it on top. . In order to improve efficiency , according to PCB The number of layers will be 1~3 A the same PCB The plates are stacked together to make holes . Last on top PCB Put a layer of aluminum on it , The upper and lower aluminum plates are used for drilling and drilling , It won't tear PCB Copper foil on .
• Next, the operator only needs to select the correct drilling program , The rest is done automatically by the drilling machine . The drill bit of the drilling machine is driven by air pressure , The maximum rotation can reach per minute 15 Wanzhuan , Such a high speed is enough to ensure the smoothness of the hole wall . The replacement of drill bit is also completed automatically by the machine according to the program . The smallest bit can reach 100 Micron diameter , And the diameter of human hair is 150 micron .
• Because in the previous lamination process , The melted epoxy is squeezed to PCB outside , So it needs to be removed . Profiling milling machine according to PCB Correct XY Coordinate to cut its periphery .

07  Chemical precipitation of copper on the pore wall

• The first step is to deposit a layer of conductive material on the hole wall , By chemical deposition throughout PCB The surface of the , It also includes the formation of 1 Micron copper film . The whole process, such as chemical treatment and cleaning, is controlled by the machine .

08 Outer layer PCB Layout transfer

• Outer layer PCB The normal method is adopted for layout transfer , Use positive plate . The outer layer PCB Layout transferred to copper foil , Use photocopied film and photosensitive film to PCB Layout transferred to copper foil .PCB The non line area is covered by the cured photosensitive film . After cleaning the uncured photosensitive film, electroplate . Where there is a film, it cannot be electroplated , And there's no membrane , First copper and then tin . Alkaline etching after film removal , Final tin removal . The circuit pattern is left on the board because it is protected by tin .
• Clean the copper foil on both sides PCB Put it into the film press , The film press presses the photosensitive mold onto the copper foil . The upper and lower layers are photocopied through the positioning hole PCB The layout film is fixed , Put... In the middle PCB plate . And then through UV The illumination of the lamp solidifies the photosensitive film under the transparent film , That is, the lines that need to be reserved . Wash away unwanted 、 After there is no cured photosensitive film , Check it . take PCB Clip in , Electroplate the copper . In order to ensure that the hole position has good enough conductivity , The electroplated copper film on the hole wall must have 25 The thickness of microns , So the whole system will be automatically controlled by computer , To ensure its accuracy .

09 Computer control and copper electroplating

• After the copper film plating is completed , The computer will also be plated with a thin layer of tin . Unload the tin plated PCB Check after the plate , Ensure that the thickness of copper and tin plating is correct .

Next, a complete automatic assembly line completes the etching process .

• First of all, will PCB The cured photosensitive film on the board is washed off . Then wash the unnecessary copper foil covered by it with strong alkali . And then the tin remover will PCB Lay out the tin plating on the copper foil to be removed . After the final cleaning 4 layer PCB The layout is finished .

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