O primeiro passo de PCB a produção é organizar e verificar o Layout do PCB. A planta de fabricação de PCB recebe os arquivos CAD da empresa de design de PCB. Como cada software CAD tem seu próprio formato de arquivo exclusivo, a planta de PCB os converte em um formato unificado – Extended Gerber RS-274X ou Gerber X2. Then the engineer of the factory will check whether the PCB layout conforms to the production process, whether there are any defects and other problems.

Em um dos PCBS caseiros, o layout do PCB é impresso em papel usando uma impressora a laser e depois transferido para uma placa revestida de cobre. Porém, no processo de impressão, como a impressora está sujeita a pontos de ruptura de deficiência de tinta, é necessário preencher manualmente a tinta com caneta de óleo.

Uma pequena quantidade de produção está bem, mas se esse defeito for transferido para a produção industrial, isso reduzirá muito a eficiência da produção. Therefore, the factory generally adopts the way of photocopying, printing the PCB layout on the film. If it is a multi-layer PCB, the layout of each layer will be arranged in order.

The film is then punched with counterpoint holes. Counterpoint holes are very important, and are then used to align materials on each layer of the PCB.

Produção de placa principal

Clean the copper clad plate, if dust may cause the final circuit short circuit or break.

The figure below is an illustration of an 8-layer PCB, which is actually made up of 3 copper-clad plates (core boards) plus 2 copper films and then glued together with semi-cured sheets. The production sequence starts from the core board (four or five layers of lines) in the middle, and is continuously stacked together before being fixed. O PCB de 4 camadas é feito de forma semelhante, mas com apenas uma placa central e dois filmes de cobre.

Transfer of inner PCB layout

Therefore, the two-layer circuit of the most central Core plate should be made first. After the copper-clad plate is cleaned, the surface is covered with a photosensitive film. The film solidifies when exposed to light, forming a protective film over the copper foil of the copper-clad plate.

Insert two layers of PCB layout film and two layers of copper clad board, and finally insert the upper layer of PCB layout film to ensure that the upper and lower layers of PCB layout film stacking position is accurate.

Photosensitizer uses UV lamp to irradiate the photosensitive film on copper foil. The photosensitive film is solidified under the transparent film, and the photosensitive film is not solidified under the opaque film. The copper foil covered by solidified photosensitive film is the PCB layout line needed, equivalent to the role of laser printer ink of manual PCB. In the paper PCB layout of the previous laser printer, the black toner was covered with copper foil to be retained. In this case, the copper foil covered with black film will corrode away, while the transparent film will be preserved as the photosensitive film solidifies.

O filme não curado é então lavado com soda cáustica e o circuito de folha de cobre necessário é coberto pelo filme curado.

Inner core board etching

The unwanted copper foil is then etched away with a strong base, such as NaOH.

Tear off the cured photosensitive film to expose the copper foil needed for PCB layout circuit.

Perfuração e inspeção da placa central

A placa do núcleo foi feita com sucesso. Then make the opposite hole in the core plate for easy alignment with other raw materials.

Once the core board is pressed with other layers of PCB, it cannot be modified, so it is very important to check. A máquina irá comparar automaticamente com os desenhos de layout de PCB para verificar erros.

As primeiras duas camadas de placas PCB foram feitas

laminado

Here we need a new raw material called semi-cured sheet (Prepreg), which is the core board and core board (PCB layer number & GT; 4), and the adhesive between the core plate and the outer copper foil, but also plays a role in insulation.

The lower layer of copper foil and two layers of semi-solidified sheet have been in advance through the positioning hole and the lower iron plate fixed position, and then the good core plate is also put into the positioning hole, and finally in turn two layers of semi-solidified sheet, a layer of copper foil and a layer of pressure aluminum plate covered on the core plate.

In order to improve work efficiency, the factory will stack three different PCB boards together and then fix them. The upper iron plate is magnetically attracted to facilitate counterpoint with the lower iron plate. Through the placement of the counterpoint needle, the two layers of iron plate counterpoint successfully, the machine as far as possible to compress the space between the iron plate, and then fixed with nails.

PCB board clamped by iron plate is placed on the support, and then into the vacuum hot press for lamination. The heat in the vacuum hot press melts the epoxy resin in the semi-cured sheet, holding the core and copper foil together under pressure.

After laminating, remove the top iron plate that presses the PCB. Em seguida, a placa de alumínio pressurizada é removida. A placa de alumínio também desempenha um papel no isolamento de diferentes PCBS e garantindo a folha de cobre lisa na camada externa do PCB. Both sides of the PCB are covered with a layer of smooth copper foil.

perfuração

How do you connect the four non-touching layers of copper foil together in a PCB? O PCB é primeiro perfurado através de orifícios e, em seguida, metalizado para conduzir eletricidade.

A máquina de perfuração de raios-X é usada para localizar a placa central da camada interna. A máquina encontrará e localizará automaticamente a posição do orifício na placa do núcleo e, em seguida, fará orifícios de posicionamento para a PCB para garantir que a perfuração a seguir seja feita no centro da posição do orifício.

Place a sheet of aluminum on the punch machine and then place the PCB on top. Como a perfuração é um processo relativamente lento, a fim de melhorar a eficiência, 1 a 3 placas de PCB idênticas serão empilhadas juntas para perfuração de acordo com o número de camadas de PCB. Finally, the top PCB is covered with a layer of aluminum, the top and bottom layers of aluminum so that when the drill drills in and out, the copper foil on the PCB will not tear.

The operator then only needs to select the correct drilling procedure and the drilling machine does the rest automatically. A broca é acionada por pressão de ar, com rotação máxima de 150,000 rotações por minuto, alta o suficiente para garantir uma parede lisa do furo.

A substituição da broca também é feita automaticamente pela máquina de acordo com o programa. The smallest drill can be 100 microns in diameter, while a human hair is 150 microns in diameter.

No processo de laminação anterior, o epóxi derretido foi extrudado para fora do PCB, por isso precisava ser removido. A fresadora corta a periferia do PCB de acordo com as coordenadas XY corretas.

Precipitação química de cobre na parede dos poros

Since almost all PCB designs use perforations to connect different layers of lines, a good connection requires a 25 micron copper film on the hole wall. This thickness of copper film is achieved by electroplating, but the hole wall is made of non-conductive epoxy resin and fiberglass board. Portanto, a primeira etapa é acumular uma camada de material condutor na parede do furo e formar um filme de cobre de 1 mícron em toda a superfície do PCB, incluindo a parede do furo, por meio de deposição química. Todo o processo, como o tratamento químico e a limpeza, é controlado por máquinas.

Fixed PCB

Limpe o PCB

Delivery of PCB

Chemical precipitation of copper film

Transfer the layout of the outer PCB

Next, the layout of the outer PCB will be transferred to the copper foil. The process is similar to that of the PCB layout of the inner core board, which is transferred to the copper foil using photocopied film and photosensitive film. The only difference is that the positive plate will be used as the board.

The transfer of inner PCB layout introduced above adopts the subtraction method and adopts the negative plate as the board. PCB covered by solidified photosensitive film is circuit, clean the unsolidified photosensitive film, exposed copper foil is etched, PCB layout circuit is protected by solidified photosensitive film. The outer PCB layout is transferred by the normal method, and the positive plate is used as the board. The area covered by a cured film on a PCB is a non – line area. After cleaning the uncured film, electroplating is carried out. Não há filme que possa ser galvanizado e não há filme, primeiro o cobre e depois o estanho. Depois que o filme é removido, o ataque alcalino é realizado e, finalmente, o estanho é removido. The circuit pattern is left on the board because it is protected by tin.

Clean both sides of the copper foil PCB into the press, the press will be sensitive to the copper foil mold pressing.

Fixe o filme de layout PCB das camadas superior e inferior da fotocópia através do orifício de posicionamento e coloque a placa PCB no meio. The photosensitive film under the transmittance film is then solidified by UV lamp irradiation, which is the line that needs to be preserved.

After cleaning the film that is not needed and has not been cured, inspect it.

Clamp the PCB and electroplate the copper. As mentioned before, in order to ensure that the hole has good electrical conductivity, the copper film electroplated on the hole wall must have a thickness of 25 microns, so the whole system will be automatically controlled by computer to ensure its accuracy.

Fixed PCB

Computer control and electroplating copper

After the copper film is electroplated, the computer arranges for a thin layer of tin to be replated.

After unloading the tin plated PCB board, check to ensure that the thickness of copper and tin plating is correct.

Gravura PCB externa

Next, a complete automated assembly line completes the etching process. First, clean off the cured film on the PCB board.

A strong alkali is then used to clean off unwanted copper foil that is covered by it.

Em seguida, o revestimento de estanho na folha de cobre do layout PCB é removido com uma solução de decapagem de estanho. After cleaning, 4 layers PCB layout is completed.