PCB board manufacturing method

How Printed circuit boards are manufactured?

In this article you will read about step by step Printed circuit board manufacturing method. As you know PCB (Printed circuit board) are used in all most in each electronic device. Millions of PCB are manufactured and used in electronic devices. So i think Printed circuit board manufacturing could be a good option to try as small business enterprises. 

Let’s understand history of PCB- Paul Eisler worked for PCB in 1936. He invented printing conducting copper circuit on non conducting board.

PCB manufacturing Process Steps


There are many method of PCB board manufacturing. Most of step are common in PCB manufacturing only  Etching method changes- Here We dipping in alkaline solution for Copper traces, or in another method we do copper plating over traces made using photosensitive lamination, then those copper traces is protected by Tin plating.

PCB manufacturing Method step by step

PCB manufacturing process diagram


Raw material for PCB manufacturing :- 

Most common raw material is copper and fiber glass sheet. Selection of correct Raw material of copper and Glass fiber sheet play important role in PCB performance.

Copper is selected because it is great conductor of electricity. GF is used because it provide mechanical strength to PCB. 1.6 mm thick FR-4 laminated copper clad on two side can also used as Raw material for PCB manufacturing. FR-4 GF is used because it is flame retardant. All PCB should be flame retardant, this is global standard requirement. 

Two type of Copper is used in PCB- 1. Electrodeposited (ED) copper 2. Rolled Annealed copper (RA).

This copper flat sheet is laminated on Flat sheet of insulating glass fiber material. Copper is kept upside and glass fiber is kept downside.

PCB raw material 


Glass fiber is the reinforced plastic. Fiberglass doesn't burn or support combustion. Also, this inorganic material is naturally incombustible. Therefore it doesn't produce smoke when exposed to heat. Glass fibers are commonly used for reinforcement of thermosetting. Most glass fibers are silica based (50–60%- SiO2) and contain a host of other oxides of calcium, boron, sodium, aluminum, iron, etc. 

Operating circuit design in CAD:-

Operating circuits are designed in CAD software and file is saved as Gerber Data. 

Gerber file contain CAD design of PCB, design of all drill location, size of drill, image, symbols and soldering location, etc. This Gerber file is saved in .gbr extension after CAD design. Gerber data is "de facto" standard used by PCB industries to describe the printed circuit board images- copper layer, solder mask, silk screening, symbols and drill data, etc.

 

Gerber File for PCB manufacturing

PCB drilling by CNC machine:-

Drilling hole is done in sheet with the help of Gerber data. (Holes used to attach the components into board later on). CNC drilling machine is used for hole drilling in PCB board.

PCB cleaning after Drilling:-

This can be done using Q-tip dipped in alcohol. We can also use brush system and chemical based system to clean the board after drilling.

Copper board drilling in PCB manufacturing


Electrolytic copper plating on PCB:-

 If copper clad sheet-Having two side copper traces, then we need to electrically connect different layer of PCB. For this thin layer of copper is chemically deposited into through holes. Later on electrolytic copper plating is done to thickened copper in holes- we called vias.

Photoresist masking on copper board:-

We cover the copper plate with resistance mask. Resistance mask will have same pattern that we want. 

Resistance Mask- It is photosensitive or photoresist (Light sensitive material-used for photoengraving) mask pasted on Copper board.  Photoresist dry film can also be used, which can be brought easily from market.



Circuit tracing on Copper board:-

First Circuit track is drawn on transparent film using Gerber file. This film have same pattern that we want, is placed over the resistive mask. UV light technique is used to draw circuit track on resistive mask. UV light remove uncovered portion of photoresist, leaving only visible copper traces.

Tin plating on copper traces:-

Now we do additional layer of tin plating over the traces. This tin layer ptotect copper from etching which will be done next operation.

Etching Process of PCB:-

Etching process is done to remove copper except visible copper track on resistive mask. For this we dip the arrangement into alkaline solution at 60 to 120 degree Celsius temperature. The area of copper uncovered by resistive mask dissolves or is etched away after process.

What is Etching?

Etching is to make an art on hard material by eating into the material’s surface. If you ever have heard of laser etching then you know in laser etching we remove material from surface to make an art over that surface.

In PCB manufacturing etching process is most important process.  It involves removing copper from the surface of the PCB in order to reveal the desired circuit pattern. So we remove unwanted copper from a printed circuit board. Here two type of PCB etching-Dry Etching & Wet etching.

Dry Etching- Plasma etching, Laser etching.

Wet Etching- Acidic Etching (Ferric Chloride & Cupric Chloride), Alkaline Etching (Ammoniacal)

Etching is chemical process – Chemical solution [chloride copper (CuCl2, 2H2O) + hydrochloride (HCl) + hydrogen peroxide (H2O2) + water (H2O)] in which we dip the arrangement.

Optical Inspection of Circuit:-

After etching process, Inspection is done through optical machine to check broken or short circuit traces.

Then we wash off & we are left with only required traces of copper.

PCB Solder Masking:-

To protect the copper traces from oxidation and dust we do solder masking.

Solder Mask coating:- It is also known as solder stop mask is thin liqueur like layer of polymer applied over copper traces to protect it from oxidation and to prevent conductive solder bridging between different component placed closed to each other on board causing short circuit.

Various types of Soldermask are available in market. 4 types of PCB soldermask:-

  1. Epoxy Liquid SM
  2. Dry Film Photoimageable,
  3. Liquid Photoimageable (LPI soldermask)
  4. Top & Bottom Side mask. (Belfin UV soldermask green color)



UV process to remove Green masking from hole edges:-

Now problem is copper traces go hidden beneath the green layer which break the connection b/w holes of copper traces. To avoid this issue we have to remove the solder mask from the edges. This could be done by covering the edges area of holes with chemical resistance mask. And then go for UV process. Because green solder mask will remain on copper traces only if we do UV light process.

Now we do chemical dipping, by this green mask of edges will be removed. Since we placed chemical resistance mask on hole edges so when UV light passed, cover area don’t adhere to copper, which is removed by chemical stripping later on.   

Silk Screening of PCB:-

We do silk screening to draw marking, Logo, Symbols. 

Next is SMT soldering of components on PCB boards.


Conclusion-

In one method we remove copper by dipping in alkaline solution and left with copper traces- In this method I think we are waste lot of copper. Because trillion no of PCb boards are manufactured in this world. Just imagine how much copper will be used to make those trillion PCBs. So I think, there should be alternative method of making PCB where we do PCB tracing, later on we do Copper plating over those traces.  By doing this we save copper. Well method is now days used, not new thing. I will write about it later, if I receive positive feedback from my readers. 

Thank You for reading, Hope you like it. you may like following article:-

What is SMT process and SMT soldering

IMDS meaning and IMDS system

 

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