Fundamentals of manufacturing operations

Fundamentals of manufacturing operations

Read this page at least once before you do anything in real.

Reading the guide

Boxed pages: for each box, read the contents of the box. Then execute the commands prescribed. Then scratch out the box to remember the operations have been done.
Info boxes in boxed pages (marked by i in blue circle ): these boxes give additional information in advance

Soldering

Basic soldering of electric joints

If the soldering iron's tip becomes dirty, heat it up and wipe it into a piece of rag or wet sponge so that it becomes clean again. If you omit this you will not be able to make a reliable joint.

-- examples of OK and wrong soldering iron tip.

Do not spare resin flux and do not waste the solder. Put there only as much tin as necessary for the joint to be firm, but do not make balls from solder. Before soldering parts together, cover them with tin using solder and resin flux (be sure the tin adheres evenly to the part). Then put them together and add some tin, resin flux, and leave the soldering iron on until all the tin becomes liquid, then remove the soldering iron and don't move the joint until it thoroughyl solidifies. The surface of the tin must be clean and shiny.

-- examples of OK and wrong joint.

The components in an airwire electronic construction must not touch each other. If the thin insulation lacquer got accidentally corrupted, the device would be unreliable then. Short circuit between the touching components would occur randomly.

If bending the wires or cutting them near the soldered joint, reheat the joint after. Mechanical stress on the wire causes the joint to crack and to become a cold joint. Remelting the cold joint again and letting it cool down correctly makes it a good joint again.

When letting the soldered joints cool down, do not move the wires. Also don't blow at the joint to make it cool down quicker. Both things result in cold joint.

Soldering SMD parts

Those tiny parts with tiny leads are called SMD. If you are using soldering gun, replace the thick wire loop with thin one that is little bit smaller. If you are using regulated soldering iron, use the one with fine tip.

Soldering 2-lead through-hole parts

You want them to not fall out and not burn your fingers:

Bend the leads
Insert the part and keep holding it with finger
Cut the leads
Glue down both leads with a drop of molten rosin
Stop holding the part
Solder both pins.

Soldering sensitive semiconductors

Do not overheat the semiconductors. If you can't get tin on the pin and would need too long time, relax and wait until the part cools and then continue. Or hold the pin with pliers between the end and the part, so that the pliers will suck off the heat spreading over the pin.

Use a soldering iron with grounded tip. If you use those gun-style irons with a loop of thick wire, connect an aligator-clip to the loop and connect it reliably electrically with the metal box. Also don't turn on or off the switch of soldering gun when touching the Q101 or something near it in the circuit. This is somewhat tricky, because normally one uses constant switching on and off of the gun to regulate the tip temperature.

Identifying electronic parts

Capacitors usually have the value printed on them. The most widespread system works like this: There is for example "104". You interpret is as 10 and 4. 10 is mantissa and 4 exponent, the unit is picofarad. So that 10*10^4pF=100nF. The capacitor's value is 100nF. Some multimeters can even measure capacitors.

Electrolytic capacitors must be polarized right. They have usually a minus (-) marker strip printed on one side. The lead that is near this marker is (-). Former Czech TESLA capacitors had the + wire marked by a groove around one edge and the - was connected with the body. Tantalum SMD capacitors have strip on + side.

Resistors have got a colour strip code on them. Decode it according to the following chart:

or take a multimeter and measure the value :)

SMD codes (by example)
Printed on part	Real value (resistor)	Real value (capacitor)
100	10*10^0=10 ohms	10pF
1000	100*10^0=100 ohms	100pF
10	10 ohms	10pF
220	22*10^0=22 ohms	22pF
685	68*10^5=6.8 Mohms	6.8uF
471	47*10^1=470 ohms	470pF
333	33*10^3=33 kohms	33 nF

Diodes have a remarkable strip on one side, which signs always the cathode. Diode is -|<|-, cathode is the -| and anode the <|-. You can check them with a multimeter - the red lead is on anode when the selector is on diode measurement and the multimeter display shows the voltage drop across the diode at some small (typically 1mA) current.

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