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Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
Pcb 101
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Pcb 101

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This is a presentation that I put together that explains the basic manufacturing process for printed circuit boards. There are many different ways to build a board. This presentation explains the …

This is a presentation that I put together that explains the basic manufacturing process for printed circuit boards. There are many different ways to build a board. This presentation explains the basics of the most common operations. This is a general overview. For more information on the subject visit www.pcbdesignschool.com

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Transcript

  • 1. PCB 101The Basics of Building a Printed Circuit Board. Presented by David Duross Engineering Director
  • 2. Inner Layer Process.● Starts with copper clad FR4.● FR4 is a composite material of woven E- glass and epoxy resin.● Referred to as a core or C-stage.
  • 3. Dry Film Lamination● Core is chemically cleaned to remove process residue or contaminates.● Core is laminated with Dry Film Photo-resist.● Cleaning operation promotes dry film bond to copper surface.
  • 4. Dry Film Laminating Equipment● The dry film is laminated onto the core by use of a cut sheet vacuum laminator.● Conveyorized processing allows any thickness material to be laminated.
  • 5. Dry Film Expose● Artwork is placed against the dry film.● The surface is exposed to high energy UV light.● The circuit pattern is exposed to UV light.
  • 6. Exposure Equipment● Automated equipment allows a hands free operation.● System automatically aligns artwork front to back for accurate registration.● Interior of unit has hepa air filtration.
  • 7. Dry Film Develop● The exposed dry film is chemically developed and made permanent.● Undeveloped dry film is rinsed away.● The dry film forms the circuitry pattern.
  • 8. Copper Etch● The copper we dont want to keep is chemically etched away.● The dry film acts as an etch resist protecting the copper we want to keep.
  • 9. Dry Film Strip● The dry film photo- resist is chemically removed.● The inner layer circuitry pattern is now formed.
  • 10. Post Etch Punch and AOI● Post etch punch automatically adds mechanical alignment positions to the core in the form of four slots.● Provides accurate alignment for multiple cores.● Panels are then inspected on a system known as an AOI.● AOI is short for Automatic Optical Inspection.
  • 11. Oxide Treatment● Copper is a very smooth surface.● The copper surface needs to be roughened up to promote bonding to epoxy resin later on. Oxide treatment does this.● FR4 after copper etch is rough enough to provide a good bonding surface.
  • 12. Multilayer Lamination● The core forms the inner layers.● Sheets of pre-preg (B- stage) are placed against the core.● Copper foil is then placed against the pre-preg.● The copper foil forms the outer layers of the printed circuit board.
  • 13. Lamination Press Equipment● Vacuum lamination systems evacuate air from the system under light pressure.● When the temperature increases beyond a control point the system applies high pressure.● Press cycles are controlled by a computerized system.● Multiple process panels are pressed at the same time in what is referred to as a lamination book.
  • 14. Multilayer Lamination● The core, pre-preg and copper foil are pressed together under a vacuum with high pressure and heat.● The pre-preg liquefies, flows and encapsulates the oxide treated copper.● The pre-preg solidifies as temperature increases.● The stack is then allowed to cool.
  • 15. Primary Drill● Holes are drilled into the pressed panel intersecting copper features on the inner layers.● Drilled holes are non-conductive.● Copper burrs at the edge of the hole are mechanically removed.● Drilling leaves an epoxy smear over the inner layer copper exposed by the drilling process.● The epoxy smear is chemically removed to ensure that the inner layer copper is exposed.● Note the location of the two holes.
  • 16. Hole Formation● Drilling is done on an automated CNC drilling system.● De-smear is either done with a plasma etch system or with a chemical process line.
  • 17. Copper Deposition / Direct Metalization● Copper deposition or direct metalization is applied to non-copper surfaces.● Material applied is very thin but conductive.● The conductive material provides the electrical pathway for electroplated copper later on.
  • 18. Copper DepositionDirect Metalization● Direct metalization coats only the epoxy and glass.● Copper deposition coats everything.● Both can be processed vertically or horizontally.
  • 19. Outer Layer Dry Film Lamination● Panel is chemically cleaned to remove process residue or contaminates.● Panel is laminated with Dry Film Photo-resist.● Cleaning operation promotes dry film bond to copper surface.● Cleaning is typically done prior to the copper deposition / direct metalization process.
  • 20. Outer Layer Dry Film Expose● Artwork is placed against the dry film.● The surface is exposed to high energy UV light.● The circuit pattern is prevented from being exposed to UV light.
  • 21. Outer Layer Dry Film Develop● The exposed dry film is chemically developed and made permanent.● Undeveloped dry film is rinsed away.● Openings in the dry film form the circuitry pattern.● Note that one of our two drilled holes is covered by the dry film.
  • 22. Copper Plate● The dry film acts as a plating resist.● The dry film covers copper we dont want to keep.● Additional copper is electro-plated onto exposed surfaces not covered by the dry film.● Copper is plated in the hole not covered by dry film.● Approximately .001” (0.0254 mm) of continuous copper is plated in the hole.
  • 23. Tin Plate● Electro-plated tin is plated directly onto the electro- plated copper.● The tin also plates into holes not covered by dry film.● The tin protects the copper we want to keep.● The plated tin is very thin.
  • 24. Outer Layer Dry Film Strip● The dry film is chemically stripped away from the panel.● Note that the hole in the center of our sample is tin plated.● The hole on the right side is not plated with tin.
  • 25. Copper Etch● The tin acts as an etch resist.● Copper not plated with tin is chemically etched away.● The hole plated with tin is protected.● The hole on the right was not copper or tin plated due to the dry film that covered it.● The copper deposition / direct metalization in the hole on the right is removed in the copper etching process.
  • 26. Tin Strip● The thin layer of electro- plated tin is chemically removed.● The tin is also removed from the center hole.● All exposed electrical conductors are now bare copper.
  • 27. Photo Image-able Solder Mask Application● A thin layer of liquid photo image-able solder mask is applied to all exposed surfaces.● The mask may be applied either by spraying or with a screen/squeegee.● The mask is a thin polymer coating roughly .004” (0.102mm) thick when wet.● The mask is tack dried for handling purposes.
  • 28. Mask Expose, Develop and Cure● Artwork is placed against the tack dried solder mask ink.● Solder mask not covered by an artwork image is exposed to high energy UV light.● Exposed mask is chemically developed and made permanent.● Unexposed mask is washed away.● The solder mask is then thermally cured.● Cured mask shall be approximately .001” (0.0254mm) thick.
  • 29. Hot Air Solder Leveling● Panels are coated with solder flux.● For vertical processing panels are dipped into a large solder pot.● For horizontal processing panels are passed through a solder fountain.● Excess solder is shaved off of the process panel with hot blowing air knives.● Solder is typically 200 micro-inches in thickness minimum.● Solder-ability is the acceptance criteria.
  • 30. Component Markings● Component markings are applied with non-conductive inks.● Markings can be any color. White is the most common.● Inks can be applied by a screen/squeegee set-up or with an ink-jet printer.● Markings typically indicate component placement and orientation.
  • 31. Marking Equipment● Ink jet printing applies a white epoxy ink sprayed as a final image and UV tack dried as the ink is applied.● Silkscreening relies on pulling a squeegee across a mesh. Openings in the mesh match the marking features.● Both techniques require the ink to be baked to ensure final cure.● UV cure-able inks are available as well.
  • 32. Final Fabrication● Individual boards are routed and or scored free from the process panel.● Specialty milling such as counter bores and sinks may be added at this step.● Boards are rinsed free of process debris and dried.
  • 33. Electrical Test● Boards are electrically tested for opens and shorts.● Testing is done on a dedicated fixture or with a robotic system referred to as a flying probe tester.
  • 34. Final Inspection● Boards are visually inspected to either customer requirements or industry standards.● Boards are measured for dimensional accuracy.● Boards are tested for ionic contamination.
  • 35. End

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