Film Room    Picture
Under controlled environmental conditions (72 F @50%R.H.) a set of master film tools are plotted using our fully automatic laser photoplotters and film processing equipment. The master film tools are then inspected and copied to diazo film for use by the imaging, screening and inspection personnel.

Innerlayer Processing
The imaging personnel start by laminating a copper clad core (innerlayer) material with a photosensitive etch resist film. Silver film tools are registered on the laminated cores and exposed with a ultraviolet light source. The innerlayer is then developed, removing the resist film from the copper in the areas that will eventually become free of copper. The exposed copper is then removed using an etching solution that dissolves the copper . Finally the etch resist film is removed revealing the finished innerlayer panel.

Multilayer Lamination
In the Lamination area the finished innerlayer panels are treated in a process that produces a dark brown/black surface on the innerlayer. This modified surface increases the adhesion of the multilayer board. The prepared innerlayers are stacked alternately with a partially cured epoxy sheet material called prepreg to create the multilayer panel. The panels are then placed in a hydraulic press and pressed under extreme pressure and heated for a predetermined amount of time. The prepreg material melts and is forced into the spaces between the interlayer conductors by the 250-300 PSI. of pressure. When the molten epoxy reaches approximately 300 F it solidifies at which time the epoxy finishes curing. When the cycle has ended the panels are cooled and removed from the press now ready for the drilling operation.

Drilling    Picture
Copper clad material from our suppliers or pressed multilayer panels are stacked up on our multi spindle CNC drilling equipment. Solid carbide drill bits are loaded into magazines and placed into the drilling machine. The program created in the CAM room is loaded into the controller and the program run. The drilling operation is fully automatic from there. The machine loads the drill bits into high speed air bearing spindles, sets the speeds and feeds rates, checks drill diameter, length, and run-out. The machine keeps track of how many holes each drill has drilled and changes them at predetermined intervals insuring optimum hole quality by limiting the life of the drill bit. It also watches for broken tools and replaces them if necessary.

Hole Activation
The hole activation is a process involving a series of chemical solutions that clean, prepare and activate the hole walls with copper, producing an electrically conductive hole. This will allow copper to electroplate to the epoxy core material creating a plated through hole. This is the start of the electrical interconnection of the internal and outer layers.

Imaging
A photosensitive resist film is laminated to the drilled panel. Diazo film tools are registered to the laminated panels and then exposed to an ultraviolet light source. The photoresist is developed revealing the copper in the areas that will eventually remain as conductors.

Plating / Etching
The imaged panels are then chemically cleaned and loaded into an electroplating tank. Copper is electroplated onto the hole walls and to the exposed conductor areas. Metal will not plate to areas masked by the photoresist film. The panels are transferred to a tin electroplating tank for a thin layer of tin plating. This tin layer is used to protect the newly plated copper from the etching process. The resist film is removed revealing the copper areas to be etched. The unwanted copper is dissolved using an etching solution leaving only the areas protected by the tin plating. The tin is then removed revealing copper conductors and land areas.

Masking    Picture
The plated and etched panels are cleaned and inspected prior to the application of the soldermask coating. The soldermask coating is then applied in a conveyorized spray machine followed by an IR tack dry. The soldermask used is called LPI (liquid photo-imageable) and is light sensitive. After tack drying, a diazo film tool is registered to the coated panel and the panel exposed in an ultraviolet light source. The soldermask coated panel is then developed which removes the mask and exposes the pads or any areas protected by the film tool. Lastly, the panels are baked to finish curing the soldermask ink.

Surface Finishing  More Info
Panels can then be sent through several different processes to produce a variety of surface finishes. The most common of which is hot air solder leveling (HASL) process. In this process the panel is chemically cleaned and flux is applied. The panel is dipped into a molten tank of solder for a few seconds and then pulled through a set of air knives. The excess solder is blown from the holes and surface of the panel as it passes through the knives. Solder does not adhere to the areas protected by the soldermask material but only to the exposed copper features.
Other surface finishes include, electroplated Gold (Au) over Nickel (Ni), Electroless Nickel Immersion Gold (ENIG), White Tin and a lead-free solder finish.
For lead-free finishes that meet the RoHS directive; ENIG, White Tin and Lead-Free Solder are offered

Marking / Legend
All of the silkscreen marking and legends applied at Nationwide are done using a LPI (liquid photoimageable) ink.  This insures the very sharpest of images for not only very small features (<.006") but also for features that are placed over high profile circuitry.

Routing
Finished panels are profiled or cut out using a CNC router.  The router is programmed to create the dimensional profile of the individual board.  Using carbide cutting bits, the machine routs the profile of the board.  The dimensions of the finished board are checked to print.  The boards are then cleaned and sent to our testing and inspection areas.

Testing and Final Inspection
Data from the customer is converted to the necessary format required by our testing equipment. The test data created will test the finished board to the customers supplied design. Individual boards are loaded onto the tester and the machine runs a sequence of electrical tests. Boards passing the electrical tests for both isolation and resistance are marked and sent to our final inspection department.