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Contribute PWB fabrication by OKUNO’s total solutions

OKUNO offers a wide range of surface treatment chemicals for the manufacturing process of printed wiring boards that are essential for electronic devices and home appliances. Explaining the typical manufacturing process of multilayer PWBs, and we introduce our product line-up to support your manufacturing processes.

Contribute PWB fabrication by OKUNO’s total solutions

  • Substrate, cutting, PWB tooling-hole drilling

    CCL (Copper Clad Laminate) is used as a substrate. Conduct board sizing and tooling-hole drilling. The tooling holes are used to align top-side and bottom-side circuits as well as inner and outer copper layers in a right position.

    Substrate, cutting, PWB tooling-hole drilling

  • Pre-treatment

    Prepare a next step, DFR (Dry Film Resist) lamination. To increase DFR adhesion, etch the surface of copper foils by jet-scrubber, buff brushing.

    Pre-treatment

  • DFR lamination

    Laminate DFR on copper foils. DFR is used as a photosensitive material for photolithography.

    DFR lamination

  • DFR exposure

    Apply masks (films, metals or glass) partly on DFR and expose light onto the whole surface. Currently, LDI (Laser Direct Imaging), which doesn’t require mask application, is increasing.

    DFR exposure

  • DFR development

    Dissolve the mask-applied (unexposed) areas with sodium carbonate solution. The masks remaining on copper foils is used as a resist for a next etching step.

    DFR development

  • Etching

    Etch copper foils with copper (II) chloride solution or an etching solution, and form circuit patterns.

    Etching

  • DFR strippingProduct name OPC PERSORRY series, BUBBRAT R-2

    Strip DFR with an alkaline solution. Stripping bathes foam by using, so anti-foaming agents are generally used.

    DFR stripping

  • Black oxide treatment

    Etch the surface of copper foils to ensure adhesion of copper foils and pre-preg (partially cured resin composite) in multi-layer fabrication process. Generally, oxidize the surface of copper foils to obtain a roughened surface. The surface of copper foils change black after this treatment, so this step is called a black oxide treatment.

    Black oxide treatment

  • Lay-up

    Laminate pre-preg and a copper foil on the both sides.

    Lay-up

  • Hot press

    Heat the laminated layers under a pressure of several tens to one thousand ton in a vacuum Melt pre-preg by heat to multi-layer PWB formation.

    Hot press

  • Drilling

    Drill PWBs to make through holes.

    Drilling

  • De-smearProduct name OPC-1000 PROCESS DS

    After the drilling step above, melted and decomposed resin components still remain onto the inner copper layers in the through hole. De-smear is conducted to remove these residues from the hole and to increase connection reliability. Also, the inside wall of the hole is etched in this process to enhance the adhesion of electroless copper plating and copper electroplating.

    De-smear

  • Electroless copper platingProduct name OPC PROCESS, OPC H-TEC PROCESS

    In copper electroplating, the plating is conducted into through holes to ensure the electric conductivity between top-side and bottom-side circuits and between inner and outer copper layers. Electroless copper plating plays a role as the first layer before the copper electroplating. Before the electroless plating, cleaning, hydrophilization, catalyzing and accelerating steps are necessary as pre-treatment steps.

    Electroless copper plating

  • Copper electroplatingProduct name TOP LUCINA series

    Increase the thickness of the plated film in the through holes by electroplating. In this process, it is important to increase the thickness of the film not only in through hole but also on the surface area of printed wiring boards in order to ensure pattern formation performance in the later etching step. Thus, high throwing power is strongly demanded to copper electroplating (acid copper plating) solutions.

    Copper electroplating

  • Pre-treatment

    Prepare a next step, DFR lamination. To increase DFR adhesion, etch the surface of copper foils by jet-scrubber, buff brushing.

    Pre-treatment

  • DFR lamination

    Laminate DFR on copper foils. DFR is used as a photosensitive material for photolithography.

    DFR lamination

  • DFR exposure

    Apply masks (films, metals or glass) partly on DFR and expose light onto the whole surface of copper foils. Currently, LDI (Laser Direct Imaging), which doesn’t require mask application, is increasing.

    DFR exposure

  • DFR development

    Dissolve the mask-applied (unexposed) areas with sodium carbonate solution. The masks remaining on copper foils is used as a resist for a next etching step.

    DFR development

  • Etching

    Etch copper foils with copper (II) chloride dehydrate solution or an etching solution, and form circuit patterns.

    Etching

  • DFR strippingProduct name OPC PERSORRY series, BUBBRAT R-2

    Strip DFR with an alkaline solution. Stripping bathes foam by using, so anti-foaming agents are generally used.

    DFR stripping

  • Solder resist application

    Apply PSR (Photo Solder Resist) on the through hole by screen printing or static printing. Film-type solder resist can be also used. Film-type solder resist is applied in a vacuum laminating machine.

    Solder resist application

  • Solder resist exposure

    Apply masks around the through hole, and expose light onto the whole surface.

    Solder resist exposure

  • Solder resist development

    Dissolve the solder-resist applied (unexposed) areas with an alkaline solution.

    Solder resist development

  • Final surface treatmentProduct name TOP ICP PROCESS, SUBSTAR SN series

    Electroless nickel/(palladium)/gold plating, electroless tin plating, solder leveling treatment (solder melting plating) are conducted for surface mounting. Before the electroless nickel plating, cleaning, catalyzing and post-dipping steps are necessary.

    Final surface treatment