A Printed Circuit Board or PCB is Mechanical Support & electrically wired the electronic components using the copper (conductive path) which is made by etching copper clad. PCB is also called as printed Wired Board (PWB). The PCB without component is raw PCB & PCB with component is called printed circuit board assembly it means the raw PCB is assembled with electronics components.
Nowadays PCB (raw) become very inexpensive especially Single sided Board (SSB) & Double Sided Board (DSB). Multi layers PCB are still costly due to its high setup charges. Single Sided Board (SSB) The Printed Circuit Board which has only one track (copper) layer is called SSB. Double Sided Board (DSB) The Printed Circuit Board which has two track (copper) layer is called DSB. Multi layer Board The Printed Circuit Board which has more than two copper layers. Material Used for Printed Circuit Board (PCB) Conductive Layer is basically is of thin copper foil the base is of glass epoxy (insulating materials) some types are as below.
(FR 6,FR 4,FR 2,CEM 1,CEM 2,CEM 3,CEM 4,370HR,BT,FR408,GETEK,Gepeg,HALOGEN FREE FR4,Hybrid,IS410,Nelco 13,Nelco ,3 Si, Polyimide, Rogers 3003,Rogers 4000, Rogers 4003, Rogers 4350, Rogers, RT/5880,,Rogers RT/6006,,Rogers RT/6010LM,Rogers Duroid, Taconic 6002, Taconic TLX-9, Thermount FR-4 printed circuit board material is commonly used Material)
Common Methods of producing printed circuit board
o Copper etching (Photo etching)
o Screen printing
o PCB Milling
From above the first two are widely used for mass production of printed circuit board.
- The Last one is using for prototype production of printed circuit board. Prototype PCB means the limited nos. of PCB which is for R & D purpose of new product or modification of existing product. The cooper etching (Photo etching) method is widely is used by large scale PCB manufacturing Companies all over world.
- Screen printing method is cost saving, but it compromise with quality. Also fine Printed Circuit Board with below 10 mil track & same spacing is very hard to achieve with this method. But still some companies are using this to manufacture the low cost Printed Circuit Boards.
- PCB milling is adopted recently for quick turn Printed Circuit Boards manufacturing. The Printed Circuit Boards are milled on cnc machine mechanically with routers (end mill). These methods save lot of time. But this method is not useful for mass production of Printed Circuit Boards. Photo etching With the below we will look the steps involved for Printed Circuit Board manufacturing with photo Etching methods.
Let's start from beginning how the Printed Circuit Boards are manufactured. Suppose I have requirement of Printed Circuit Board I will search the Printed Circuit manufacturer in my region with competitive rates. Select one from them. First I have to send the gerber files to him for quotation in that I have to mention few things about my requirement Such as PCB thickness, PCB finish copper, Masking, silk screen color (By default it is masking PISM green, silk is white), HAL, Lead free, Delivery time. When this data reach to Printed Circuit Board manufacturer he studies the data & gives the quotation. Following are Factors which play vital role deciding the price of Printed Circuit Board. Quantity, Minimum track, spacing & minimum drill diameter (Keep minimum track thickness & spacing between two connection 6 to 8 mill to reduce cost) Always verify the output (gerber data) before sending it to manufacturer.
Manufacturing of Printed Circuit Boards
After accepting quotation the PCB manufacturer goes for pre-engineering of gerber data. This is done in Cam department of the company or many service beuro are available which provide cost effective service to Printed Circuit Boards Industry.
Why service beuro? Saves expense on OEM license cost Saves expense on Salary, bonus & other benefits of Employee. Also the service beuro provide cost effective Solution on the other hand you have to increase salary, bonus & other benefits of employee on regular basis. What Cam dept do after getting the customer data? Cam dept. carefully studies the gerber data. If found any required missing file the customer is informed immediately. When all information & data is received, the cam dept. starts the pre-engineering of the job.
In pre-engineering the Engineer checks following things.
* Minimum Gap (pad/pad, pad/trace, trace/trace) It should be 0.006" (0.15 mm) to avoid expensive PCB
* Minimum Track Width It should be 0.006" (0.15 mm) to avoid expensive PCB
* Copper Voids The acceptable size is over 0.006", Voids below this should be patch with copper fills.
* Annular Ring It should be 0.008" either side this should be check with drill diameter not finished diameter
* Masking openings The mask opening minimum 0.002" either side. Oversize masking should be modified so that track exposure avoided.
* Unterminated traces Some times in hurry designer skip the connection & in gerber unterminated traces occur.
Next to this the PCB data is panelized according to order quantity. These details also can be found on cam service under the heading Penalization of PCB Drill file rout file is extracted (prepared) Penalization includes step & repeat. The data is multiple & venting & thieving bars are added around borders of panel.
