How to make the inner circuit

- Apr 23, 2016-

The copper foil substrate is first cut to a size suitable for pcb assembly production. Before the substrate is pressed, the copper foil on the copper surface is usually roughened by brushing, micro-etching, etc., and the dry film photoresist is closely adhered to it at an appropriate temperature and pressure. The substrate with the dry film photoresist is sent to the ultraviolet exposure machine for exposure, and the photoresist is polymerized after being irradiated with ultraviolet rays in the light transmitting region of the film (the dry film in the region will be in the later development and copper etching step). It is retained as an etch resist) and the line image on the film is transferred to the dry film photoresist on the board.

After the protective film on the film surface is peeled off, the unexposed area on the film surface is developed and removed by using an aqueous solution of sodium carbonate, and the exposed copper foil is etched away with hydrochloric acid and a mixed solution of hydrogen peroxide to form a line. Finally, the dry film photoresist that has been retired is washed away with an aqueous solution of sodium hydroxide.

For the inner layer circuit board of six or more layers, the riveting reference hole of the interlayer line is punched out by the automatic positioning punching machine. The finished inner circuit board shall be bonded to the outer layer copper foil with a glass fiber resin film. Before pressing, the inner layer needs to be blackened (oxygenated) to increase the insulation of the copper surface passivation; and the copper surface of the inner layer is roughened to produce good adhesion to the film.

When laminating, the inner layer circuit boards of six or more lines (including) are first riveted by a riveting machine. Then, the plate is placed neatly between the mirror steel plates and sent to a vacuum laminator to harden and bond the film at an appropriate temperature and pressure. The pressed circuit board uses the X-ray automatic positioning drill target machine to drill the target hole as the reference hole for the alignment of the inner and outer lines. Make the appropriate cutting of the edge of the board to facilitate subsequent processing.

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