Production Process
Production Process
1. CAM/CAD PPREPARATION
1) Data processing
2) Pattern films
3) Drill & CNC
The gerber data provided by customer will be analyzed together with other pcb documentation, specification and requirements.
Our engineers will evaluate received data against manufacturability and communicate directly with customer or pcb designer in case of any questions will arise.
Prepared gerber data will be used for photofilms plotting, drilling and milling programs.
2. INNER LAYER IMAGE
1) Cut Material
2) Coat Resist
3) Print Image
Multi-layer fabrication begins with the selection of an inner layer core and thin laminate material of the proper thickness.
Material will be cut to fit the size of production panel of exact pcb.
A light sensitive film or photoimage-able “resist” is then applied over the copper surface of cut sheets.
Panels are then exposed to a high intensity ultraviolet light source coming through the inner layer film.
Clear areas allow light to pass through and polymerize (harden) the film resist thus creating an image of the circuit pattern.
3. INNER LAYER ETCH
1) Develop
2) Etch Copper
3) Strip resist
The exposed core is processed through a chemical solution or developer that removes the resist from areas that were not polymerized by the light.
Then the copper is chemically removed from the core in all areas not covered by the dry-film resist. This creates the copper pattern that matches the film pattern.
After etch, the developed dry-film resist is chemically removed from the panel leaving the copper on the panel. Traces, pads, ground plane and other design features are now exposed.
4. AOI
1) AOI
Inner layers are then inspected against design rules using data from the gerber files.
If allowed and practical, some repairs can be made at this point. Information on defects is shared with the appropriate departments to correct any process problems.
We do not allow to repair open circuit (to weld or to bond interrupted tracks).
5. OXIDE TREATMENT
1) Brown Oxide
After inspection the panels are chemically treated to improve adhesion of the copper surface.
Often is used organic chemistry that turns copper color to dark brown.
6. LAMINATION
1) Multilayer Lamination Press
Cores with roughened copper surface now are ready to bond with Preimpregnated Bonding Sheet (PrePreg) in between, on top and bottom of the stack.
Copper foil added over PrePreg on top and bottom of the stack (outer layers).
Inner layer core, copper foil and PrePreg are bonded together under heat and pressure, sometimes in a vacuum during the lamination process.
The result is a panel with several layers of copper inside as well as the foil on the outside.
7. DRILLING
1) Drill Panels
Holes of various sizes are drilled through the panel or a stack of panels.
The locations of holes are determined by the pcb designer to fit specific components and to create interconnections between inner layers.
After drilling panels will be deburred (removed the raised edges of the metal or burrs surrounding the holes that occur during the drilling)
and desmeared (removed thin coating of resin that appears inside the hole due to heat produced by motion of the drill bit).
8. DIRECT METALLIZATION
1) Copper Deposition
Once the smear is removed, a thin coating of copper is chemically deposited on the hole walls.
9. OUTER LAYER IMAGE
1) Coat Resist
2) Print Image
3) Develop
The same resist or light sensitive film used on the inner layers is used for the outer layers. The film covers the entire surface including the drilled holes.
After dry film lamination the panel is exposed and developed using the same procedure used for the inner layer cores. Clear areas in the film allow light to pass through and
harden the resist creating an image of the circuit pattern. All of the drilled holes that are exposed will be plated through.
10. PLATING
1) Plate Cu & Tin
The electroplating processes that electrically plates copper onto the exposed metal surfaces is next. The copper will be plated up to a thickness of approximately 25μm.
The copper plating step is followed by plating tin onto all the exposed copper surfaces.
The tin will be used as an etch resist to maintain the copper traces, hole pads and walls during the outer layer etch process.
11. STRIP / OUTER ETCH / TIN STRIP
1) Strip Resist
2) Etch Copper Externals
3) Tin Strip
Strip Resist. The developed dry film resist is now removed from the panel. The tin plating is not affected. Any holes that were covered with resist are now open and will be non-plated.
This is the first step in the “strip-etch-strip” process.
Etch (second step). Copper is now removed from all parts of the panel that are not covered by tin. The tin resists the chemicals used to etch away the copper. Only the pads and traces from the artwork are left behind on the panel surface.
Then the tin is chemically removed leaving behind a bare copper and laminate panel. The surface pads, traces and plated through holes are the exposed copper. This is the last step in "strip-etch-strip" process.
12. AOI
Panels are inspected using Automatic Optical Inspection Machine against design rules using data from the gerber files.
If allowed and practical, some repairs can be made at this point.
We do not allow to repair open circuit (to weld or to bond interrupted tracks).
13. SOLDERMASK
1) Coat Soldermask
2) Print SM Image
3) Develop Soldermask
After panels are cleaned and surface is roughened to increase soldermask adhesion, a photo-sensitive epoxy based ink is applied, completely coating the panel. It is then dried to the touch but not final cured.
Using a method identical to image, the panels are exposed to a light source through a film tool.
Then the panel is developed exposing the copper pads and hole defined by the artwork. Soldermask is cured to increase surface hardness and resist soldering.
14. SURFACE FINISH
1) Customer Choice
Depending on customer requirement, pcb surface will be finished with a HASL or Lead Free HASL, ENIG, ENEPIG, Immersion Tin, Immersion Silver, Galvanic Gold or OSP.
SILKSCREEN (if required)
Ink is silkscreened onto one or both sides of the panel depending on the requirements of the customer.
The printing usually describes component placement, part number or name, date code, logo or other specified information. Panels are then baked to cure the ink.
15. ROUTING
1) Separate Parts
After surface finish and silkscreen process the boards are cut to size on a CNC machine or router.
Most panels have the individual parts routed out into single pieces or arrays of varying sizes.
Boards or arrays can also be scored (V-cut) so that they can be easily broken apart after assembly.
Chamfers, slots, countersinks and bevels are added during the rout & fabrication processes.
16. ELECTRICAL TEST
1) Test
Boards are tested for opens and shorts in the circuitry, in one of the last steps of production.
Test programs can be loaded directly onto various types of test machines or used to create specific fixtures and test programs.
Test program will identify opens and shorts. Shorts are repaired when possible and retested for verification.
We do not allow to repair open circuit (to weld or to bond interrupted tracks).
17. FINAL INSPECTION
1) FQC & Ship
Boards are visually inspected to assure they meet requirements of IPC standard and specification of actual pcb, checked dimensions, hole sizes, hole plating, solderability, etc.
Boards and meeting the acceptability standards and specific requirements are packed in ESD plastic vacuum packages, and shipped in boxes using customer preferred delivery method.
Isruties 30, LT-06221 Vilnius, LITHUANIAa
+370 5 275 4877
+370 5 275 4877
sales@pcbbaltic.lt