In recent years, SMOBC method and graphic electroplating method are two typical processes for the manufacture of double face metallized printed circuit boards. Process traverse method is also used in some specific situations.
1. Graphic plating process flow
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 > clean electrical on-off testing — > — > Screen printing resistance welding graphics — — — — > > curing screen printing mark symbol — — — — > > curing processing — — > dry cleaning – > appearance inspection — — — — > > packing finished products.
In the process, “electroless thin copper plating -> electroless thin copper plating” can be replaced by “electroless thick copper plating”, both of which have advantages and disadvantages. Graphic plating – etching method of double face metallized plate is a typical process in the 1960s and 1970s. In the 1980s, SMOBC (bare copper overlaying resistance welding film) developed gradually, especially in the manufacture of precision double-sided PCB board.
2 smobc technology
The main advantage of SMOBC plate is to solve the solder bridge short circuit phenomenon between thin lines, at the same time, due to the constant ratio of lead to tin, has better weldability and storage than hot melt plate.
There are many methods to manufacture SMOBC plate, including standard graphic plating minus method and then retracting lead and tin SMOBC process. The SMOBC electroplating process using the subtractive method of tin plating or tin dipping instead of electroplating lead and tin; SMOBC process by plugging or masking hole method; Addition method SMOBC process, etc. The SMOBC process and SMOBC process flow of graphic electroplating method for reducting lead and tin are mainly introduced below.
The SMOBC process of retracting lead and tin by graphic electroplating is similar to that of graphic electroplating. 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 — — > the contour machining of mark symbols > dry cleaning – > finished goods inspection — — — — > > packing finished products.
The main technological process of hole 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 the hole and clean the ink plug.
In the process of hole blocking, if not using ink blocking and screen printing imaging, but using a special mask type dry film to cover the hole, and then exposure to make a positive figure, this is the mask hole technology. Compared with the blocking method, it no longer has the problem of cleaning ink in the hole, but it has higher requirements for masking dry film.
The foundation of SMOBC process is to make bare copper hole metallized double-sided PCB board first, and then apply hot air leveling process.