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PCB Prototype Manufacturing Process

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Mon, Jul 27, 2020

There is a lot that goes into the manufacture of PCBs.

Being a key component of a wide range of electronics and other electrical components, they constitute a mainstay of modern technology.

As much as the manufacturing part is of prime importance, equally important is that of the prototyping process.

A process that precedes the manufacturing process, prototyping is a standard industry practice across the world.

To begin with, a general background in prototyping would prove to be of immense help.

Prototyping is the process by which a PCB design is tested out, through the creation of physical samples, from existing schematics and blueprints.

It is done in order to test the final outcome, and see if any changes are necessary, before the PCB design enters mass production.

The reason it is done is to ensure that there aren't any design flaws or other issues down the line when the PCBs are put to the use they were intended for.

Some of the key details about the PCB prototyping process are listed out in the points below.

1.) Design

One of the first steps in the manufacture of PCB prototypes is that of the design.

This is the stage where the basic design of the PCBs are drawn and then scrutinized for potential improvements that can be made.

The blueprints are then sent to a third party for verification quite often, in order to get a second opinion about the same as well.

2.) Bill of Materials

"Bill of Materials" is a reference to all the materials that would be required for the manufacturing of the PCB.

Think of it as an electronic version of "ingredients" that are necessary to create the final recipe.

3.) Routing Designs

The routing stage involves the design of the routing, which is the creation of traces, which are used to connect the various elements of the PCB.

Several things need to be taken into account at this stage, which includes, but not limited to power levels, signal noise generation, noise sensitivity, and so on.

Done largely automatically using software applications, the exact process is largely automated, with very little to no effort being required on part of the designer. This can be a fairly lengthy process, especially in the case of large boards, which have complex schematics.

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4.) Design Checks

Design checks are not so much a one-time thing, but a repetitive process.

Given that each stage of the design process adds another layer of functionality, there is the risk that the will be issued with the functionality later on, due to a host of reasons.

It is, therefore, necessary to ensure, that adequate design checks are carried out all throughout the process, in order to prevent any potential faults in the future.

5.) Photo Film Creation

From the design schematics, a photo film is created, which will be used in the design of the final PCB prototypes.

It will mark those areas of the board, which indicate those areas that are made up of conductive copper layers, and others which are non-conducive.

6.) Inner Layer Printing

This is the step when copper is added to the substrate material.

 Starting with the pre-bonding of copper to the substrates, and then another layer of photoresist, the entire assembly is exposed to UV light.

 It acts as a hardening agent, which then leaves a layer marking the areas of difference between the hard copper circuitry, and the rest of the board.

7.) Layer Alignment & Fusing

This is applicable in the case where there are multiple layers to be added to the final board design.

The boards are aligned in the right manner, after which the assemblies are fused together.

8.) Hole Drilling

This is the part where the holes are drilled in the boards, whether using mechanical or laser drills, for the insertions of vias.

It is a standard process that takes place in all major PCB designs, regardless of their purpose.

9.) Copper Plating

The circuits of the board begin with the copper plating stage, which provides the principal layer to set up create the circuitry.

The process itself involves electroplating, where a thin layer of copper is deposited on the board, after which the excess is etched away. The plating stage often takes place

10.) Final Etching

The final step in the etching process is more akin to erosion more than anything else, where chemical solutions peel away excess layers of metallic deposits.

The finished results, in turn, form the basis for further design work, whether it is the placement of additional components or anything else.

11.) Solder Mask & Surface Finish Application  

Next, a layer of solder mask is applied on the PCBs, as a protective layer to prevent the copper traces from oxidation.

A layer of finish is also added for a similar purpose as well, which is typically made of silver or gold, as it allows for the solder to spread properly across the surface of the PCB, yielding better results.

12.) Silk Screen Application & Cutting

The silkscreen application is the stage where critical information about the board is added.

The stage is followed by the cutting stage, where the individual chips are cut from the larger board, and prepared for testing and other applications.

13.) Testing & Evaluation

Last but certainly not least, is the stage where the testing and evaluation takes place.

Once the final  PCB prototype  has been created, it will need to be tested for functionality, design flaws, potential improvements, and other details. The actual testing and evaluation may be done either by one's own experts, a third party, or the company carrying out the prototyping.

This is necessary, as quite often, the final design often falls short of the expectations one had in the beginning. It would mean anything from making minor adjustments to a complete redesign of the PCB blueprints, in order to get the desired results.

Typically, one may go through several stages in the PCB design process, before they get an ideal board to put into mass production.

As a whole, these are some of the key aspects of prototyping, and everything that goes into it.

Do note that there is a lot more to this than the above, with the above being just a general introduction and a guide to the PCB prototyping process.