Tecnology of PCB

- Feb 03, 2018-

The printed circuit provides the following functions in electronic equipment:

Provide mechanical support for fixed and assembled electronic components such as integrated circuits.

To realize wiring and electrical connections or electrical insulation between various electronic components such as integrated circuits.

Provide required electrical characteristics such as characteristic impedance.

Provides for automatic solder resistance welding graphics, providing identification characters and graphics for component instrumentation, inspection and maintenance.

PCB process

The film substrate is the leading process of printed circuit board production, and the quality of film substrate directly affects the production quality of printed board.When producing a printed circuit board, there must be at least one set of corresponding films.At least one film plate should be used for each type of conductive pattern (signal layer circuit graphics and ground, power layer graphics) and non-conductive graphics (resistance welding figures and characters) of the printed board.Through photochemical transfer process, various graphics are transferred to the production board.

The purpose of film plate production is as follows:

Graphic transfer of photoreceptors, including line graphics and photoresist welding graphics.

Screen template in screen printing process, including resistance welding graphics and characters.

Machine processing (drilling and external milling) CNC machine tool programming basis and drilling reference.

With the development of the electronic industry, the demand for printing plate is higher and higher.Printing plate design high density, thin wire, small aperture trend is becoming faster and faster, the printing plate production process is also more and more perfect.In this case, if there is no high quality film, it can produce high quality printed circuit board.The production of modern printing plate requires the following conditions:

The size accuracy of the film must be consistent with the precision required by the printing plate and should be compensated for the deviation caused by the production process.

The graphic of the film should meet the design requirements and the graphic symbol is complete.

The image edge of the film is straight and neat, the edge is not weak;Black and white contrast is big, meet the photosensitive processing requirement.

The material of the film should be of good dimensional stability, that is, due to the change of environment temperature and humidity, the size change is small.

Double panel and multilayer plate film, the welding disk and the public figure of the overlap precision.

Each layer of the film should be clearly marked or named.

The film base can be used for the wavelength of light wave required, and the wavelength range is 3000- 4000A.

Before making the film version of the film, it is necessary to make a photocopy of the film, and then make a copy of the film.This year, with the rapid development of computer technology, the production process of film version has also developed greatly.Using the advanced laser light painting technology, greatly improve the quality of the production speed and the blank, and the ability to produce high precision, fine line graph, the past can't complete the PCB production CAM technology perfect

Copper Clad Laminates (abbreviated as CCL), or Copper Clad Laminates or Copper Clad Laminates, are substrate materials for the manufacture of printed circuit boards (hereinafter referred to as PCB).The most widely used etching method is the PCB, which is the etching of selected lines on the copper foil plate to obtain the desired pattern of the line.Copper clad laminates on the whole printed circuit board, mainly responsible for the conduction, insulation and support three aspects of functions.The performance, quality and manufacturing cost of the printed board depend to a great extent on copper clad laminate.

Basic manufacturing process.

The printed plate can be divided into single, double-sided and multilayer printed boards according to the number of layers of the conductor.The basic manufacturing process of single panel is as follows:

Foil sheet -- -- -- -- > > cutting drying plate (to prevent deformation) -- > pattern -- -- > wash and drying > sticker (or screen printing) - > exposure imaging (or corrosion resistant ink) - > etching -- -- -- -- -- > > to membrane electrical on-off test - > cleaning - > screen printing resistance welding graphics (printed green oil) -- -- -- -- > > curing screen printing mark symbol -- -- -- -- > > curing drilling > shape processing -- -- > dry cleaning > inspection -- -- -- -- > > packing finished products.

The basic manufacturing process of the two panels is as follows:

In recent years, the typical process of making biface metallized printing plate is SMOBC and graphic electroplating.Process conductors are also used on certain occasions.

1. Graphic electroplating process.

Foil sheet -- -- -- -- > > cutting benchmark percussive drill hole -- -- > CNC drilling test - > > deburring - > thin electroless copper -- -- > thin copper electroplating > inspection -- -- -- -- > > brush plate sticker (or screen printing) - > exposure imaging (or curing) -- -- -- -- -- > > check fix board graphics plating ten Sn/Pb (Cn) -- -- -- -- > > to membrane etching -- -- -- -- > > check fix board plug nickel plating gold-plated > hot melt cleaning -- - > electrical on-off test -- - > clean process -- -- > screen printing resistance welding graphics -- -- -- -- > > curing screen printing mark symbol -- -- -- -- > > curing processing -- -- > dry cleaning - > appearance inspection -- -- -- -- > > packing finished products.

The process of "electroless copper -> plating thin copper" can be replaced by "chemical plating thick copper", each of which has its own advantages and disadvantages.Graphic electroplating - etching a double - face metal plate is a typical process in the 60s and 70s.During the 1980s, the naked copper-clad coating technology (SMOBC) developed gradually, especially in the manufacture of precision double panels.

2. Naked copper coating (SMOBC) process.

The main advantage of SMOBC board is to solve the short circuit of solder bridge between fine lines, and it has better solderability and storage than hot-melt plate due to the constant proportion of lead tin.

There are many ways to make SMOBC board, with standard graphic electroplating minus the SMOBC process of lead tin.Use of tin plating or tin plating to replace the electroplating of lead-tin and SMOBC process;Blocking or masking of SMOBC process;Addition method SMOBC process and so on.The following is mainly about the SMOBC process of graphing electroplating and SMOBC process of plugging and SMOBC.

The SMOBC process of retracting lead tin is similar to graphic electroplating process.It only changes after etching.

Double-sided copper-clad boards - > according to the graphic plating process to the etching process > pewter back -- - > check -- -- -- -- -- - > > cleaning resistance welding graphics - > plug nickel plated gold plated -- -- -- -- > > plug stick tape hot air leveling -- -- -- -- -- - > > cleaning screen printing mark symbol - processing - > appearance > dry cleaning - > finished goods inspection -- -- -- -- > > packing finished products.

The main process flow of plugging method is as follows:

Double cladding foil plate -- -- > drilling > electroless copper -- > the whole plate electroplating copper -- -- -- -- > > blocking screen printing imaging (as) -- -- > etching go > screen printing materials, blocking material -- -- -- -- > > cleaning resistance welding graphics -- -- > plug nickel plating and gold plated > plug stick tape -- -- > hot air leveling > below working procedure and the same to the finished product.

The process of this process is simple, the key is to plug hole and wash the hole of the ink.

Method in the blocking process if you do not use blocking and screen printing ink blocking imaging, while the use of a special kind of masking type dry film to cover up a hole, then exposed as graphics, this is masking technology.Compared with the plugging method, it no longer has the problem of cleaning ink in the hole, but it has a higher requirement for masking dry film.

SMOBC process is based on the first production of bare copper hole metallized double panel, and then applied hot air leveling process.

PCB engineering

For the production of PCB, PCB, because many designers do not understand the PCB production process, so the design of circuit diagram is just the basic circuit diagram, and cannot be directly used in production.So it is necessary to modify the line file before actual production and editing, not only need to produce can film figure for the factory production process, and need to make corresponding punch, open module according to the data, and other data that would be useful for production.It is directly related to the subsequent production projects.This requires engineering and technical personnel to understand the necessary production technology, to master relevant software production at the same time, including common circuit design software, such as: Protel, Pads2000, Autocad, etc., should be more familiar with necessary CAM software such as: View2001, CAM350;GCCAM etc, PCB design input, CAM shall be included to circuit graphics edit, calibration, repair and puzzle, disk as dielectric materials, and the output light painting, drilling data and test automation.