Rapid PCB Prototyping

The end-to-end rapid PCB prototyping process involves the following stages:

Schematic Design

The important aspects of this phase are the choice of the right panel size and grid. In addition, the schmatic design includes crucial information on the use ofcomponents. At the end of the first schematic, simulations using specialized tools are run so that any errors can be spotted. The design is then converted with a netlist.

Routing Design

Designing of the routing involves looking at various factors such as;

• Power levels
• Signal noise generation
• Noise sensitivity, and more

The netlist is used at this stage to figure out optimal routes based on the number of layers and other factors.

The design stage also involves continuous checking for thermal issues such as heat spots. In addition, other checks involve:

• Design rule check
• LVs check
• Electrical rule check
• Antenna check
• Other quality assurance checks

Creating the Photo Film

Using the design, a photo film of the PCB is created. It has markings for parts that are copper conductive and non-conductive.

Printing the Inner layers

Copper is now applied to the substrate and then a layer of photoresist is applied. This is hardened with UV light. Unhardened photoresist is then removed. This is followed by removing of the hardened photoresist.

Aligning the Layers and fusing them

If it is a multi layer PCB, the layers are aligned correctly. The layers are then fused in two stages- layer-up and bonding.

Drilling the Holes

Holes are next drilled into the stack. To target the correct hole location, an x-ray locater is used.

Copper Plating

This involves depositing a layer of copper on the panel surface. Precision is of importance in this stage.

Outer Layer Imaging

A layer of photo resist is applied to the panel to image the outer layers.

Copper and Tin Plating

Another round of copper plating is undertaken. The presence of the photoresist layer ensures that copper only deposits on the desired parts. This is followed by tin plating.

Etching

Any excess copper is removed. The tin plating, in turn, protects the copper.

Solder Mask

The panel is cleaned and solder mask is applied. UV light then hardens the film. Any unhardened parts are subsequently removed.

Surface Finish

The right surface finish, basis the environment in which the PCB has to function, is next applied.

Silkscreen

Silkscreen is then applied to the surface of the PCB. The writing conveys important information about the board.

Cutting

Post a final electrical test, the board is cut using a router or a v-groove.

Assembly

At this stage the required components are added to the board:

Solder Paste Stenciling

Application of solder paste is next carried out. A stencil is placed over the PCB so that the solder paste is only applied to areas where the components need to be affixed.

Pick and Place

A pick and place machine places surface mount components on top of the soldering paste.

Reflow Soldering

This process solidifies the solder paste by running the PCB through a reflow oven. The board is heated up and then cooled so that the SMDs are permanently attached to the board.

Inspection and Quality Control

The board is checked for any errors. These include:

• Manual checks
• Automatic Optical Inspections
• X-Ray inspection
• Testing for functionality and connection quality

Inserting Through-Hole Components

If the board requires plated through-hole components, they are plated at this stage. This cannot be done through soldering paste. This has to be done either through manual soldering or wave soldering.

Functionality Test

This is the final step that simulates the operating conditions that the PCB will be exposed to, to check efficacy.

In case multiple designs of the prototype PCB are available; it will also help to run identical tests and compare results. Detailed testing at this stage ensures there are minimal issues at a later stage. Once you are fully satisfied with the design, you are ready for a full production run.