PCB Technical - The manufacturing process of double-sided PCB

The most common process types for double-sided PCB are SMOBC and pattern electroplating. There is also a process wire method, which is usually customized for some special needs. The following editor will focus on the process of SMOBC and pattern electroplating. Process.

Double-sided PCB

1. Graphic electroplating process

Foil Clad Laminate --> Blanking --> Punching and Drilling Benchmark Holes --> CNC Drilling --> Inspection --> Deburring --> Electroless Plating of Thin Copper --> Electroplating of Thin Copper --> Inspection --> Brushing --> Filming (or screen printing) --> Exposure and development (or curing) --> Inspection and repairing --> Graphic plating (Cn ten Sn/Pb) --> Film removal --> Etching --> Inspection and repair board --> Nickel-plated and gold-plated plug --> Hot melt cleaning --> Electrical continuity detection --> Cleaning treatment --> Screen printing solder mask pattern --> Curing --> Screen printing marking symbol --> Curing --> Shape Processing --> Washing and Drying --> Inspection --> Packaging --> Finished Product.

In the process, the two processes of "electroless plating of thin copper --> electroplating of thin copper" can be replaced by a single process of "electroless plating of thick copper", both of which have their own advantages and disadvantages. Pattern electroplating---etching method to make double-faced metallized plates is a typical process in the 1960s and 1970s. In the mid-1980s, the bare copper-clad solder mask process (SMOBC) gradually developed, and has become the mainstream process especially in precision double-sided panel manufacturing.

2 SMOBC process

The main advantage of SMOBC board is that it solves the short-circuit phenomenon of solder bridging between thin lines. At the same time, due to the constant ratio of lead to tin, it has better solderability and storage properties than hot melt board .

There are many ways to manufacture SMOBC boards, including the SMOBC process of standard pattern electroplating subtraction and lead-tin stripping; the subtractive pattern electroplating SMOBC process of using tin plating or immersion tin instead of electroplating lead-tin; the plugging or masking hole SMOBC process ; Additive method SMOBC process and so on. The following mainly introduces the SMOBC process and the plugging method SMOBC process flow of the pattern electroplating method and then the lead and tin stripping.

The SMOBC process of pattern electroplating followed by lead and tin stripping is similar to the pattern electroplating process. Changes only after etching.

Double-sided copper-clad board --> According to the pattern electroplating process to the etching process --> lead and tin removal --> inspection --> cleaning --> solder mask pattern --> plug nickel plating and gold plating --> plug sticking tape --> Hot air leveling --> Cleaning --> Screen printing marking symbols --> Shape processing --> Washing and drying --> Finished product inspection --> Packaging --> Finished product.

The basis of the SMOBC process is to first produce a bare copper hole metallized double-sided board, and then apply a hot air leveling process.

The main process flow of the plugging method is as follows:

Double-sided foil-clad laminate --> drilling --> electroless copper plating --> electroplating copper on the whole board --> plugging holes --> screen printing imaging (positive image) --> etching --> removing screen printing materials, Removal of plugging material --> Cleaning --> Solder mask pattern --> Nickel-plated and gold-plated plug --> Plug tape --> Hot air leveling --> The following procedures are the same as the above to the finished product.

The process steps of this process are relatively simple, and the key is to plug the holes and clean the ink that plugs the holes.

In the hole plugging process, if the hole plugging ink and screen printing imaging are not used, a special masking dry film is used to cover the hole, and then exposed to make a positive image, this is the masking hole process. Compared with the hole blocking method, it no longer has the problem of cleaning the ink in the hole, but it has higher requirements for masking the dry film.