Continental J. Engineering Sciences 7 (3): 7 - 13, 2012
© Wilolud Journals, 2012
Printed in Nigeria
ISSN: 2141 – 4068
http://www.wiloludjournal.com
doi:10.5707/cjengsci.2012.7.3.7.13
DEVELOPING THE SKILL IN PRINTED CIRCUIT BOARD FABRICATION FOR SELF RELIANCE
Ndubuisi Paul D. I.
Department of Electrical/Electronic Engineering, Akanu Ibiam Federal Polytechnic, Unwana, Ebonyi State.
email Address: ndudarla@gmail.com.
ABSTRACT
Printed circuit Board (P.C.B.) is the most popular breadboard with which designed proto-typed electronic circuits are
used to implement desired design objectives. Developing the skill in its fabrication process can be an avenue to entrench
entrepreneurship leading to self-actualization. This paper presents the techniques that are involved in the development
of this skill. To drive home this message, a two stage amplifier circuit is used to demonstrate the technique. If this is
strictly studied, followed and applied, it is enough to equip any literate electronics engineering professional and related
disciplines with the skill to accomplish P.C.B. fabrication to suit any circuit of one’s choice.
Keywords: Breadboard, Electronics, Skill, Amplifier, Development, Entrepreneurship.
INTRODUCTION
To say that unemployment in Nigeria has reached a crises point is to state the obvious. Millions of our graduates are
today roaming the streets of our big cities in search of the non existing jobs.
Perhaps, it is in an attempt to stem the tide that the planners of our educational system are enriching the curricular at
all levels with entrepreneurship development strategies. The essence of this is to awaken the consciousness of
entrepreneurial acumen in our undergraduates. An entrepreneur is someone who engages in business enterprises,
often with some personal financial risk (Robinson, 1999). The need to develop the frontiers of entrepreneurial
education among our youths lies in the fact that our Government can no longer shoulder the responsibility of being
the only employer of labour, coupled with the trend the world over where majority of the working population is
employed in the private sector. If the dreams of our political leaders in making Nigeria join the group of the
industrialized nations of the world by year 2020 is to be visible then, there is need for us to align with the word
trend. To do this, we must now start to develop small and medium scale enterprises (SMEs). These entrepreneurial
centers can be established at individual or group levels. Successful entrepreneurial venture can empower individuals
leading to economic self-reliance.
Developing and mastering the skill in the fabrication process of Printed Circuit Board (P.C.B). is obviously one of such
entrepreneurial enterprises which are capable of opening a window of opportunity for the sustenance of professionals in the field
of electronic engineering and related fields. P.C.B. is a copper clad board on which one can build a prototype electronic circuit.
The Printed Circuit Board is composed of two elements, the base and the copper conductor. The base is a thin board of insulating
material made of epoxy bonded glass fibre or synthetic resin bonded paper. It can be in either rigid or flexible forms. The base
supports the copper conductor paths and through the base, all the components are fixed. Thus, the base material provides
mechanical support to all copper areas, all the components soldered to the copper and any other component or part that are
fastened to it to facilitate interfacing. The second element of the P.C.B., the copper conductor is a set of very thin copper strips
designed into various shapes and firmly attached to the base material. The function of the copper is to provide attachment point
for the soldering of component leads and to provide electrical connection between components. Although, there are other
materials on which electronic circuits is built, such as Solderless breadboard and Matrix Vero board, the P.C.B. offers a
professional solution (Arihilam, 2007). Indeed, P.C.B. is the most modern and widely used breadboard. It is very useful in the
mass production of electronic circuits. It is also advantageous in maintenance as it exists in card or module form and thus can
promote module substitution in repairs. Its use in industrial electronic circuits has brought a lot of relief in the previous rather
expensive and tedious hard wiring manufacturing methods practiced before its advent. It is important that this technique of P.C.B.
fabrication is made popular among young engineers. Developing the skill in the layout design or artwork design and the eventual
fabrication of the P.C.B. is indeed an avenue to entrench entrepreneurship. This
7
Ndubuisi Paul D. I: Continental J. Engineering Sciences 7 (3): 7 - 13, 2012
obliviously will enthrone self-actualization leading to a boost in national economy. This is what our country needs
now.
Printed Circuit Board (P.C.B) fabrication process
According to Leonida (1989), printed circuit board (P.C.B) fabrication can be done in three different modes. These
modes are: 1, by depositing a pattern of conductive ink on a base of insulating material. 2, by etching a wiring
pattern on copper that is coated on either phonetic polyester, glass polyester or glass epoxy material, and
3, by photo-engraving the wiring pattern on a copper clad material.
Out of these three modes, etching a wiring pattern on copper clad with an insulating material is the most popular.
Fabrication processes can be illustrated with the block diagram shown in figure 1.
Layout
design
Pattern
transfer
Fabrication
proper
Fig 1. Block diagram of P.C.B. fabrication process.
The layout design process
Layout design is an artwork of how the electronic components are placed and interconnected among itself on a
printed circuit board (Brown, 1990). It is the most tasking and the most important process in the P.C.B fabrication. It
requires artistry in the proper and orderly arrangement of components on the P.C.B. in order to economize space and
minimize the waste of materials. Below are suggested guide on how to produce a good P.C.B. layout design.
1.
(a)
(b)
(c)
(a)
(b)
(c)
Choose the number of P.C.B. you are going to employ in the implementation of a given electronic circuit
diagram. There are a number of reasons that make it necessary to use more than one P.C.B for a given
electronic circuit. Some of than are:
Volume of component in the circuit and the consequences of its weight.
Assembly technique, such as the level of portability of the electronic system.
The environmental consideration at which the system is to be used, such as shock and vibration
environments. Thus, if the schematic diagram of the electronic system you are going to produce its layout
design is large, you have the choice to sub-divide it into stages or group of stages with each stage having a
separate P.C.B. layout design. Some of the benefit of using more than one P.C.B. for a large electronic system
includes:
Layout design for each P.C.B. is relatively easier.
Etching process and testing assembled P.C.B. is also easier.
Maintenance of faulty system is easier as substitution repair is encouraged.
2.
On each P.C.B. decide on how to mount the components, such as auxiliary mounting or horizontally mounting.
The later is the most popular.
3.
Calculate the total surface area of all the physical components as contained in each stage and call it (S).
4.
Choose the size of the layout diagram of the P.C.B. To do this affectively, you must be mindful of the
following.
(a)
That 2.5 mm copper conductor surface diameter are usually allowed around hole positions where
component legs are to be inserted on the P.C.B. hence enough clearance is required around hole positions.
(b)
The larger the current required to be carried by the P.C.B. conducting track, the wider the track should be
(Arihilam 2007). Considering the fact that majority of electronic circuit elements including logic gates are
low current and low voltage demanding devices, a minimum P.C.B conducting track width of one
millimeter is advised.
8
Ndubuisi Paul D. I: Continental J. Engineering Sciences 7 (3): 7 - 13, 2012
(c)
(d)
The wider the P.C.B. insulation path the larger the size of the P.C.B. and the lesser the beauty of the layout
design. For this reason, it is recommended that you aspire to achieve a minimum insulation path clearance
of one millimeter.
The closer the ratio of the component total surface area (S) over the size of the chosen P.C.B. (X)
approaches 50 percent, the better the aesthetics of the layout design. The choice of X=2S ie 1:2 is for the
professionals. For the beginners, a choice of X=4S could be ideal.
5. In producing the layout design, the following points must be noted.
(a)
That component crossing over each other must be avoided.
(b)
That the use of cable jumper is minimized as much as possible.
(c)
That integrated circuit (IC) where in use should be placed first and at the center of the P.C.B. layout design
diagram, while other subsidiary components are placed around it.
(d) The I.C. pin positions must be numbered in their correct order. A useful method of doing this is to place the
I.C. on the reverse side of your drawing paper, press the I.C. firmly into the paper, invert the paper and pick out the
pin numbers.
(e)
If the P.C.B. is a mother board or panel board, then adequate female connectors must be provided at the
appropriate position for the insertion of other P.C.Bs. that make up the system.
(f) If the P.C.B. is not a mother board, then edge connectors must be provided for the connections of the P.C.B. to
the mother board or panel board.
(g) Enough out line space must be provided for blanking and location of hole on the P.C.B. for mechanical
anchorage.
(h) Ideally, layout out diagrams most not be the same with the schematic diagram with respect to the physical
positioning of components, however, the electrical connections must be the same.
6. Start the layout design with a sketch of the draft artwork of your wiring arrangement on a plain sheet of paper.
7. When satisfied with (6) above, them reproduce the sketch carefully on a graph draughting paper, taking note of
all the physical sizes of your circuit components and other conditions as outlined above that will ultimately enable
you achieve a standard layout design of your P.C.B. The use of drawing tools and templates, precision grid and
tracing papers are very useful in positioning components and producing accurate layout diagrams. Computer
software such as Electronic workbench, Autocad, etc can also be used.
Pattern Transfer
Pattern transfer is a term that explains how the wiring pattern (layout diagram) of your electronic circuit, which is now in a
perfect draft artwork form is super-imposed unto a copper clad material for etching. Below are the procedures to follow in doing
this.
1. Cut out the copper clad material with a hark saw to provide a panel of the size of your layout diagram.
2. Clean the copper side of the board with methyl alcohol and dry with a paper towel or by gently rubbing the surface with
smooth sand paper.
3.
Place a carbon paper between the copper and your layout diagram and with a used ball pen or center punch mark, reproduce
the layout diagram on the copper. You can use the punch to make dots on the carbon paper and connect them up with a ruler.
The pattern is thus printed on the copper clad material, or said in another way, the pattern is transferred unto the P.C.B.
Photoengraving using ultra violet light and developer is a more advanced technology.
The Etching Process.
In this process, the non conducting path or insulation path of the copper is removed from the copper clad material. The end result
of this process is the P.C.B. which is now a replica of the layout diagram. Etching process takes the following procedures.
1.
Punch holes on the P.C.B. to provide spaces where components are to be connected and for mechanical anchorage of the
P.CB. on the chassis. To punch holes by drilling, it is advised that the P.C.B. should be clamped with a flat piece of wood.
The wood will support the back of the P.C.B. as the drill penetrates it.
2.
Use etch resist pen to screen print all conductive areas required on the final P.C.B; noting the requirements for conducting
track width and around hole positions.
3.
Allow the ink to dry under room temperature.
4.
Dip the P.C.B. into an etching solution. Diluted Ferric chloride is the most popular. The solution should be wormed up to
about 40OC for a more successful etching. Exposing the solution under sunlight in a sunny
9
Ndubuisi Paul D. I: Continental J. Engineering Sciences 7 (3): 7 - 13, 2012
5.
6.
7.
8.
day for 15 to 30 minutes may be enough to achieve a good result. The chemical will dissolve all the copper in
the P.C.B. not covered by the etch resist ink.
Wash off the chemical from the etched P.C.B. using clean water and allow to dry.
Strip off the etch resist ink carefully. This can be done by robbing a suitable chemical such as trichloroethylene
on the P.C.B. with a rotating brush.
Other preservatives such as
(a)
Solder resist ink may be applied along copper conducting tracks to avoid unwanted sticking of solders
during soldering which could course short circuit and
(b)
Solderability preservation ink may also be applied around hole positions to eliminate incidence of hard
soldering between the components and the copper conducting tracks.
As is required in any production process, each stage of the P.C.B. fabrication process requires careful
inspection testing for early detection and correction of possible occurrences of errors and mistakes (Wakerly,
1976). The absence of errors and mistakes mean that the P.C.B. is ready for use. Component can be inserted,
soldered, tested and installed in the system for use.
Sample Demonstration of Layout Design
Lenk (1995) showed the schematic diagram of a two-stage 13watt audio-Amplifier. This is as shown in figure 2 and
is used to demonstrate the production of the layout design. The total surface area(S) of the components in figure 2, is
computed as shown in table 1.
From table 1, it is seen that the total surface area of components (S) = 23.065 cm2 which approximates to 24 cm2 .
A ratio of X : S ie 1 : 2.5 is targeted. Thus the total surface area of P.C.B. (X) = 2.5S = 2.5 x 24 = 60cm2 .
Let the dimension of the P.C.B. be 10cm x 6cm. That is, length = 10cm, and width = 6cm
The sketched layout diagram of the P.C.B. for implementing the schematic diagram of figure 2 is as shown in figure
3.
The final P.C.B. which is designed with strict adherence to the instructions given in the layout design process of the
P.C.B. production are as shown in figures 4, 5, and 6.
This diagram can now be transferred into a P.C.B, etched accordingly, components connected in them and tested
okay for use.
CONCLUSION
Careful analysis of this demonstration of the layout design of a moderate audio amplifier circuit with a twelve leg IC
shows that wire jumper occurred only in two places J1 and J2. It is also important to note that the ratio of total
component surface area(s) over that of that size of the P.C.B.(X) is 40%. The 50% professional standard
recommended for a good layout design can be achieved with determination over time with reasonable practices.
When this is done, then the journey towards equipping a litrate electronic engineering practitioner with the skill to
accomplish P.C.B. fabrication for his electronic circuit has just begun.
An entrepreneur in this business will not only be self reliant in building his own circuit but also become a consultant
to other enterprising organizations in this era of information communication technology.
10
Ndubuisi Paul D. I: Continental J. Engineering Sciences 7 (3): 7 - 13, 2012
Figure 2. Schematic diagram of a thirteen watt audio amplifier with four speakers output, one microphone and an
auxiliary input.
Table 1. Determination of the total surface area of components in
Figure 2.
S.N
Description of components
Dimension in
cm
1
IC, HAI588
2X1
2
Transistor, Q1, BC 184
1 X 0.5
3
Resistor R1, .. R11
2 X 0.5
4
VR1,VR2 (may not be on the PCB)
___
5
Electrolytic capacitor
1
6
Mica capacitor
1. X 0.5
7
Switch (may not be on the PCB)
___
8
LED
”
___
Total
23.065
Unit
1
1
11
2
9
5
1
1
C.S.A of
unit in cm2
2
0.5
1.0
___
0.788
0.5
___
___
Total C.S.A in
cm2
2
0.5
11.0
___
7.065
2.5
___
___
Figure 3. Sketch of the layout design of figure 2.
11
Ndubuisi Paul D. I: Continental J. Engineering Sciences 7 (3): 7 - 13, 2012
Figure 4. Layout diagram on P.C.B. showing copper conductor pathways
with components mounted.
Figure 5. Conductor pathways on the P.C.B.
Figure 6. Components mounted on the P.C.B.
12
Ndubuisi Paul D. I: Continental J. Engineering Sciences 7 (3): 7 - 13, 2012
REFERENCES
Arihilam, E. C. (2007). Production of Electronic Printed Circuit Board in Schools. Journal of Science and
Engineering Development, 1 (2), 2 - 6.
Brown, W. C. (1990). Drafting for industry . New Delhi, India: Good heart-Willcox Company.
Lenk, J. D. (1995). Handbook of simplified solid state circuit design. New Jersey : Prentice Hall.
Leonida, G. (1989). Handbook of Printed circuit Board design, manufacturing, Component and Assembly. New
York U.S.A.: Electrochemical Publishers.
Robinson, M. (1999). Chambers 21st century Dictionary. Edinburgh, U.K.: Chambers Harrap. Publisher.
Wakerly, J. F. (1976). Logic design projects using Integrated Circuits. London, U.K.: Joho Willy and Sons.
Received for Publication: 11/06/12
Accepted for Publication: 25/09/12
13