A printed circuit board, also called PCB, serves, in simple terms, as a carrier for the components and the connections of the components to each other and to the outside, which together form the circuit. In most cases, the carrier material serves as an insulator, while the connection between the components is made by copper tracks.

Here, the PCB combines mechanical attachment and electrical connection as its most important properties. PCBs are used as an irreplaceable base in almost all electronic devices.

Carrier material and connections on the PCB

Glass fibre fabric (FR4/5), polyimide foil (Flex), aluminium, Teflon and ceramics are used as the electrically insulating carrier material of the PCB.

Electrical connections consist mainly of copper tracks for SMD components or wiring for THT components.

Components and assembly

The majority of components are soldered onto this surface as SMD (Surface Mounted Device) components or THT (Through Hole Technology) components are mounted via through-hole assembly.

The term PCBA (Printed Circuit Board Assembly) or "electronic assembly" from PCB assembly refers to the printed circuit board equipped with components. By embedding components, the PCB is no longer just a carrier of components but has sometimes become part of the circuit itself.

Types of PCBs

A PCB can be single-sided , double-sided or consist of several layers. If a PCB has several layers, it is called a multilayer. With multilayers, each layer offers space for its own circuit, so that much more complicated circuits can be realised.

Double-sided and multilayer PCBs are the most common type, with multilayers being used for more complicated applications. Flexible PCBs are used to save space and to make flexible connections between mechanical parts.

The data required to create the PCB is entered in layout programs such as EAGLE, Altium or TARGET 3001! (downloadable free of charge from the Beta LAYOUT page) and sent to the PCB manufacturer or, as on the Beta LAYOUT page, processed by drag & drop.

The process is described here for rigid PCBs, flexible PCBs, which Beta LAYOUT also sells, require a modified process.

CAM editing
The data records of the customer are converted into the Ext. Gerber format (RS 274X).
The processed output file in the Extended Gerber Format can be supplied as preview if desired.
A pre-production preview of the PCB layout can be supplied in PDF format.

Order tracking

Material Preparation
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 1.6mm thick base material, with a coating of 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.

CNC Drilling
With the help of CNC drill machines the through-hole plated and component drills are produced. During this process, spindle speeds of up to 230,000 revolutions per minute are recorded.

WATCH''ur''PCB Step

Through-hole plating
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.

Brushing
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.

Resist laminating
Under extreme temperatures and pressures the entire PCB-POOL panel is laminated with a photosensitive dry resist (LAMINAR 5038).

Resist exposure
Using the previously generated photoplots the resist is exposed to UV light.

WATCH''ur''PCB Step

Developing the resist
The exposed panel is developed in a 1% sodium carbonate solution as it goes through a continuous flow system. This gives the individual PCBs on the panel their structure.

Structure of the conductor pattern in electroplating

Conductor image structure in the electroplating
The tracks and pads which are developed, free of photo resist, are copper-plated to a thickness of approx. 35µm and fused with a 6µm -10µm tin film, protecting the tracks and pads during the final etching process.

Resist stripping and removing tin from the circuit board

Resist stripping
The photoresist is stripped away with a 2.5% caustic potash solution. This lends itself to the immersion and spray coat processes.

Etching
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.

Tin stripping
Only then will the tin be removed using a nitric acid based tin-stripper. This lends itself to the dipping or spraying processes.

WATCH''ur''PCB Step

Applying the solder resist to the circuit board

Applying the solder mask
The solder mask is applied over the entire area using in a spray method.

Exposing the solder mask
Using a direct exposure laser, the solder mask is exposed with the highest possible precision.

Developing the solder mask
The development of the exposed production panel is in turn achieved through a continuous flow system in a 1% sodium solution. Hence all soldering points and pads, which are to be tin plated later, are cleared of solder mask.

Apply silk screen to printed circuit board

Silk screen
Using a digital inkjet printer, the silk screen is immediately printed onto the solder mask.

Burning in the solder resist on the circuit board

Burning-in
At a temperature of approx. 150°C, the solder mask receives its final hardening in a continuous oven.

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Application of the ENIG Hal surfaces to the boards

Surface finish

Chemical Nickel-Gold
The pads developed free of the solder mask are coated with chemical Nickel-Gold surface through vertical baths. The gold layer acts as a protection of 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 270° C. During this process the PCB is immersed in liquid tin which is blown off with preheated air under a pressure of approx. 5 bar.
The data sheet for the used lead-free tin can be found with our specifications.

WATCH''ur''PCB Arbeitsschritt

Pinning
To prevent the panel from moving during routing, it is pinned down onto the routing machine bed.

Milling the panel of printed circuit boards

Milling
The individual PCBs are removed from the production panel with the help of a CNC milling machine. A spindle speed of 40,000 rpm and a feed rate of 1 m/min. is used for this.

Multilayer

Laminating the resist
Under high temperatures and pressures the production panel is laminated with a photosensitive dry resist.

Exposing the resist
Using a direct exposure laser, the resist is exposed with the highest possible precision.

Developing the resist
The exposed inner layers are developed in a 1% sodium carbonate solution as it goes through a continuous flow system

Pressing
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.