Basics tools for circuit designing

PRINTED CIRCUIT BOARD(PCB)

When making the circuit with the electronic parts of the resistors, the capacitors, the transistors, the ICs and so on, it is necessary to connect the lead line of each part appropriately. Also, each part must be fixed, too.

The printed circuit board is used to do the wiring among the parts and the fixation of the part.
The electronic circuits can be assembled even if it doesn't use the printed circuit board. It uses the wiring materials for the wiring and it should use the terminal board and so on for the fixation of the parts. Actually, the simple circuit sometimes assembles the printed circuit board without using it, too.

There are some advantages which use the printed circuit board.
a)Good one is made: Many sheet of the same circuits can be made with the same quality. The same one is made whoever assembles.


b)Cheaply made: If fixing (the soldering) in the parts even if it doesn't wire, the electronic circuits can be assembled.It is possible to do the
construction at short time and it can do the manufacturing cost cheaply.All constructions can be mechanized, too.

c)Compactly made: The small wiring can be made using the print technique.

As the description up, the printed circuit board very suited the construction of the electronic circuits.

The printed circuit board is also called PWB(Printed Wiring Board).


2)The structure of the printed circuit board:

The printed circuit board is doing the structure which stuck the wiring in the insulation board(Material such as the bakelite, the epoxy which doesn't transmit electricity) with the 1 to 2 mm thickness with the copper foil.

As for the thickness of the copper foil, the one of 30 to 40 µm is general.


3)cutting of pcb board:
The PCB must be cut according to the size of the circuit to make.

Also, it is mainly related with the size of the equipment to incorporate the PCB into.

Last edited by rajeev on Sat Aug 22, 2009 10:16 pm; edited 1 time in total

SOLDERING

The soldering is the basic work for electronic circuit engineering. I will introduce the tools for soldering below.
The sufficient attention is necessary during work, because soldering handles a high temperature.
Pay attention to the handling of the soldering iron sufficiently, because it becomes burn, fire more, carelessly.

Soldering iron

Soldering iron is a necessary instrument when you solder.
Solder is hardening in a normal temperature, but solder can melt easily by using the soldering iron and the parts and wiring materials can be fixed to the printed wiring board(PWB).
The important piont is temperature of the soldering iron.
For soldering, it needs to become the temperature of the object(PWB, parts, wire etc) to solder melting temperature.
However, the temperature of soldering iron must not be too high. The electronic component gets damage with high temperature. So, you need to solder in a short time.
Sometimes, the loose contact of soldering occurs. It is difficult to confirm only by looking at. When the temperature of the object is not enough, the loose contact will be occured.
At the end of assembling of the electronic circuit, you need to check the soldered contact with circuit tester etc.

Electric power (Calorific value is decided with this)

There are various kind of soldering irons. I am discussing only 3 kinds of soldering irons.

25W type: This type is convenient when solder the parts on PWB.

80W type: use this type when solder the parts to thick copper plate.
In case of thick copper plate, the heat is easy to escape and the temperature rise is difficult.

15W type: use this type for the part which is easy to break by the heat.

Usually, 25W type is enough.

The tip of iron


The soldering is done at the tip of iron. So, the tip of iron is very important.
There is the type that the tip of soldering iron is made of copper stick. But I don't recommend that type.
Because, the copper stick rusts easily by heat and it becomes difficult to convey heat.
Also the tip of copper stick melts with solder. It becomes difficult to sloder.
I recommend the one that is using a special metal for tip. It is difficult to rust and melt.
The tip of iron must keep clean.
When it get dirty, it becomes difficult to convey heat.



Soldering iron stand

The soldering iron becomes high temperature.
Therefore it can't be placed on the desk directly.
The stabilized soldering iron stand is necessary.

When making the electronic circuit, sometime I forgot the existence of soldering iron, because I have devoted to the parts, wiring etc. It was serious when I noticed, desk was burning.
You need to choose the iron stand with appropriate weight which can hold iron stably.
Also you need to choose the iron stand that fit the form of iron.


Solder

The solder is the alloy of lead and tin.
As for good solder, the containment rate of tin is high. The finish of soldering is beautiful. The price is a little bit high.
There are several kinds of solder, solder wire( thread form solder ) is convenient for electronic circuit making.
This solder wire is doing the structure of the pipe and flux is included inside. Flux melts together with the solder and the solder becomes easy to attach to the component leads.
There are some thickness of solder wire. prefer to use the one that diameter is 0.5 mm. The containment rate of the tin is 60%.

Solder sucker

The failure of soldering occurs often. In this case, the part or the wiring must be removed.
I will introduce the instruments that can be used for desoldering.

Solder pump

This is the tool that can be absorbed the melted solder with the repulsion power of the spring that was built in with the principle of the piston.
The usage is shown below.
Pushe down the knob of the upper part of the pump against to spring until it is locked.
Melt the solder of the part that wants to absorb solder with iron.
Apply the nozzle of the pump to the melted solder part.
Push the release knob of pump.
Then the plunger of the pump is pushed up with the power of spring and solder is absorbed inside the pump.
You need to do this operation quickly, otherwise the part gets damage by the heat. A little practice is needed.



Desoldering wire
This is made of thin copper net wire like a screen cable in a coaxial cable.
Like water inhales to cloth, the solder is absorbed to the net wire by a capillary tube phenomenon.
The usage is shown below.
Apply the desoldering wire to the part that wants to take solder.
Apply the soldering iron from the top and Melt the solder.
The melted solder is absorbed to desoldering wire with a capillary tube phenomenon. At this time you absorb solder while shifting desoldering wire.
When the solder can not be removed in the once, remove repeatedly while shifting the desoldering wire.

There are several kinds of width of desoldering wire.prefer to use the one with 2mm width.

HOLDING AND CUTTING


When you make an electronic circuit, the work which does the component lead of parts straight or bends the lead or cuts the lead is needed.
When handling a small part, the tool that the tip is sharp is needed.

Needle Plier


This is the plier with thin cutting tip.
It is very convenient to restrain, and also to hold the parts at narrow place.
It is used to make straight the component lead.
I think that a smaller one is convenient than a big one.
This tool is necessary to electronic circuit making.


Wire Cutter (Nipper)


This tool is used when cut the wire or cut the component lead.
The one that the top is pointed is good.
Even this, the small one is convenient.
There is a type that a ditch for the wire cut is put to the blade.
It isn't possible to use when the thickness of the wire doesn't fit.
Be careful so as not to be injured because the blade is sharp.
This tool is necessary to electronic circuit making.

WIRING MATERIAL

Wire is used to electrically connect circuit parts, devices, equipment etc.
There are various kinds of wiring materials. On this page, I introduce the type that is used for the assembly of electronic circuits.

The different types of wire can be divided largely into two categories: single wire and twisted strand wire. It really doesn't matter which kind you use for a given application, but usually, single wire is used to connect devices (resistors, capacitors ect) together on the PWB. (Parts that don't move)
It is also used for jumper wiring.
Twisted strand wire can bend freely, so it can be used for wiring on the PWB, and also to connect discrete pieces of equipment.
If single wire is used to connnect separate equipment, it will break soon, as it is not very flexible.

It is convenient to use the single tin coated wire of the diameter 0.32 mm for the wiring of PWB. If the diameter is larger, soldering becomes a little bit difficult. And if the diameter is too thin, it becomes difficult to bend the wire the way you want it to stay.
It's best to use whatever wire you are comfortable with, and not worry about those things.



If you want to connect separated parts on the PWB, twisted wire covered with soft insulation material is most convenient for wiring.
It's convenient to wire the circuit using different color wires for different purposes. Otherwise, wiring the circuit with many wires the same color gets confusing.

The photograph shows several colors of twisted wire.
It is called 0.12/7PVC.
The pictured wire is comprised of 7 tin coated wires 0.12 mm each in diameter, covered by very thin PVC plastic.