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Any manufacturer has its own modus operandi. The process described hereunder is a typical process to manufacture Printed
Circuit Boards.
Once the order(s) received by the manufacturer, Gerber data, Drill data, Fabrication drawing will be transferred to the engineering
department for review. The engineering department will go through a checklist consisting of rules to make sure the design can be
manufactured. Once that completes, tooling will be generated. Tooling consists of NC drill file, NC Rout file, Photo Plotting of
the art-work and a Net List testing File.
If it concerns a multilayer board, the inner layers laminate are cut with the proper copper weight and cleaned before sending to
the dry film department. Inner layers are coated with a dry film material so the imagine may transferred and developed. The Inner
layers are then etched to remove unwanted copper, leaving the board image and subsequently the Inner layers are placed in a Black
Oxide Tank, which is to protect all inner layer copper through the heat lamination process. Inner Layers are stacked in sequence
with proper Prepreg in between the layers and with copper foil on the outside to produce the Multilayer Panel. Depending on the
type of the material, the lamination process can take from 90 minutes or longer at 350 degree F or higher.
Once pressed, these panels are treated as a double sided and ready for drilling. This is done by NC machines and carbide drills.
The next process is electroless copper plating, which is copper deposited into the hole barrels.
The panels are coated with a dry film material which is applied by putting the panels through hot roll laminator. Outer layers
Images are transferred to the panels through a exposing process and then run through a developer. At this time, only traces and
areas that are to be conducted are exposed, the rest are covered with dry film.
Next is the Plating process, copper is to plated to the traces and hole walls. Panels are placed in plating racks and dip into the
plating tanks. Depending on the amount of copper needed to plate the Amps and Time is set for the current to go through the panels
to meet those needs. Normally one hour of plating time at 25AMPs per SQUARE foot is sufficient to achieve 1 oz of copper in the
holes and on the surface. Also tin is applied to the surface.
After Plating, panels are then placed into a Stripping Tank to remove all the dry film resist. The exposed copper (after dry film
stripped) without plating is ready for etch off. The tin protects the copper circuitry from being etched. The panels are then run
through a Tin Stripper leaving only Copper over Circuitry (Bare Copper).
A soldermask is flooded onto the panels using a screen process. Panels are then tack dry in an oven with a low temperature for a
short period of time before taking to dry film. Here, the SolderMask Images are transferred to the panels through exposing process.
It then develops through a soldermask developer to remove all soldermask on pads and holes. It then is placed in an oven and baked
for final cure at 350 degree for about 2 hours. Mask is then permanently on the panels.
Legend or Silk Screen is screened onto the panels using a screened stencil, with white Non Conductive Ink. This image of the
legend is then transferred onto the panels with all information of components and their locations. Panels are again placed on a
rack and put in to a oven for approximately 10 -15 minutes for curing of the legend.
Panels are then put through a Hot Air Solder Leveler (HASL). This process adds solder to the surface of pads and inside
the holes for assembly.
CNC Routing process is the one of the last processes. Panels are aligned by tooling and pinned to stack of Back-Up material on
the CNC table. Using the appropriate routing and, depending on the requirements, difference router bits to use to cut the boards
to it final shape and dimensions.
Electrical Testing of each individual board takes place using Bed of Nails (conventional) or Flying Probe Test (Fixtureless),
depending on the technology of the designs and or the quantity of the orders.
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