The manufacturing process
The data records from the various software solutions supported in the PCB-POOL are standardized in the Ext. Gerber Format (RS 274X).
The processed output file in Ext. Gerber Format can be supplied as preview.
The copper-clad panels along with the drill entry material & a back-up-board are then cut to size.
The standard panel comprises of a 0.062 inch thick base material, with a coating of 0.5 ounce (18µm) copper on each side.
Drilling and pinning
At this stage the reference & tooling holes are drilled. The PCB-POOL panel is then pinned onto the CNC machine.
With the help of CNC drill machines the through-hole plated and component drills are produced. During this process, spindle speeds of up to 100,000 revolutions per minute are recorded.
Now an electrographic film (e.g. Palladium) is electroplated to the wall of the drill cavity, this allows for galvanisation with copper to occur at a later stage.
Because PCBs must be completley free of grease and dust, they are subjected to rigourous cleaning (e.g. by brushing) before proceeding to the next stage.
Under extreme temperatures and pressures the entire PCB-POOL panel is laminated with a photosensitive dry resist (LAMINAR 5038).
Using the previously generated photoplots the resist is exposed to UV light.
Through cyclic construction the exposed panel is developed in a 1% sodium carbonate solution. The PCBs are now ready for plating.
Electroplated Conductor Configuration
The tracks and pads which are developed, free of photo resist, are copper-plated to a thickness of approx. 1,378mil (35µm) and fused with a 0,24mil - 0,39mil (6µm -10µm) tin film, protecting the tracks and pads during the final etching process.
The photoresist is stripped away with a 2.5% caustic potash solution. This lends itself to the immersion and spray coat processes.
The next step is the spraying on of a coat of ammonia solution onto the copper film, getting rid of any excess copper, while the galvanised tin protects the tracks and pads.
Only then will the tin be removed using a nitric acid based tin-stripper. This lends itself to the dipping or spraying processes.
The soldermask can be applied as a dry film or a liquid lacquer in a hanging casting implement. After this comes the screen-printing and spraying processes.
Finally, using the previously generated photoplots the soldermask is exposed to light.
The development of the exposed PCB is in turn achieved through a cyclic construction in a 1% sodium solution. Hence all soldering points and pads, which are to be tin plated later, are cleared of soldermask.
Using a Direct Legend Printer, the silkscreen is immediately printed onto the soldermask. In this process the printhead sprays the screen-print, defined by Gerber data, directly onto the PCB.
At a temperature of 302°F (150°C) the soldermask is tempered over a period of approx. 60 minutes.
Chemical Nickel-Gold (ENIG)
The pads freely developed by the solder paste are coated with Chemical Nickel-Gold together with the surface by means of vertical baths. The gold layer is used to protect the nickel surface to ensure solderability.
The advantages as opposed to HAL are stress-free coating and the flat surface.
Hot Air Levelling (HAL)
On the surface coating the pads are tin plated in a hot-air tin-plating system at a temperature of around 518°F (270°C). During this process the PCB-POOL panel is immersed in liquid tin which is blown off with preheated air under a pressure of approx. 72,5 psi (5 Bars).
The technical specifications sheet for the lead-free tin which is used can be found by clicking on the following link: Specifications.
To prevent the panel from moving during routing, it is pinned down onto the routing machine bed.
In the final stages, the individual PCBs are routed from the PCB-POOL panel with the aid of a CNC Routing machine. This operation involves spindle speeds of over 40,000 revs per minute and a feed rate of 1m/min.
Under extreme temperatures and pressures the internal layers are laminated with a photosensitive dry resist (LAMINAR 5038).
Using the previously generated photoplots the resist is exposed to light.
Through cyclic construction the exposed inner layers are developed in a 1% sodium carbonate solution.
Only at this stage are the individual layers pressed in a Multi-layer press at a max. temperature of 175°C and a cyclic time of 90 minutes for the layer structure.
The next stage is drilling. The following manufacture process is equally valid for both multi-layer and double-sided PCBs.