Week 9

Title of Activity : Soldering process

Objective :
To develop the complete circuit and connected between another components on the PCB board to functioned it

Content/ Procedure :

Soldering is defined as the joining of metals by a fusion of alloys which have relatively low melting points. In other words, using a metal that has a low melting point to adhere the surfaces to be soldered together. Consider that soldering is more like gluing with molten metal, unlike welding where the base metals are actually melted and combined. Soldering is also a must have skill for all sorts of electrical and electronics work. It is also a skill that must be taught correctly and developed with practice.

Soldering Equipment

The Soldering Iron/Gun

Soldering iron is the heat source used to melt solder. Irons of the 15W to 30W range are good for most electronics/printed circuit board work. Anything higher in wattage and will risk damaging either the component or the board. If need in soldering heavy components and thick wire, then use an iron of higher wattage (40W and above) or one of the large soldering guns. The main difference between an iron and a gun is that an iron is pencil shaped and designed with a pinpoint heat source for precise work, while a gun is in a familiar gun shape with a large high wattage tip heated by flowing electrical current directly through it.

Prepared to solder

1) Tinning The Soldering Tip

Before used it, I tinned the solder. Tinning is the process of coating a soldering tip with a thin coat of solder. This aids in heat transfer between the tip and the component that I soldered, and also gives the solder a base from which to flow from.

2) Warm Up The Iron

I warmed up the soldering iron. I make sure that it has fully come to temperature because then I melt a lot of solder on it. This is important if the iron is new because it may have been packed with some kind of coating to prevent corrosion.

3) Prepared A Little Space

While the soldering iron is warming up, I prepared a little space to work. I moistened a little sponge and placed it in the base of my soldering iron stand or in a dish close by.

4) Thoroughly Coat The Tip In Solder

5) Clean The Soldering Tip

Soldering A Printed Circuit Board (PCB)

1) Surface Preparation

I cleaned the board down to shiny copper which is I use a solvent such as acetone to clean any bits of the cleaning pad that may remain and to remove chemical contamination from the surface of the board. Methyl hydrate is another good solvent and a bit less stinky then acetone. Be aware that both these solvents can remove ink, so if your board is silk screened, test the chemicals first before hosing down the entire board.  

2)  Component Placement

After the component and board have been cleaned, I placed the components onto the board. I start with the smallest and flattest components which are resistors, ICs, signal diodes, etc. and then work up to the larger components which are capacitors, power transistors, transformers after the small parts are done. This keeps the board relatively flat, making it more stable during soldering. It is also best to save sensitive components (MOSFETs, non-socketed ICs) until the end to lessen the chance of damaging them during assembly of the rest of the circuit.  

In the image below, a resistor soldered and held in place by slightly bent leads.

3) Apply Heat

4) Apply Solder To The Joint

Once the component lead and solder pad has heated up, I soldered. I started with touched the tip of the strand of solder to the component lead and solder pad, but not the tip of the iron. When everything is hot enough, I soldered freely around the lead and pad.

5) Inspect The Joint and Cleanup

Last but not least, I used a small set of side cutters and cut at the top of the solder joint to trim the lead.

Result and analysis :

Backview of PCB board after being soldered

The completed circuit after soldered

Conclusions :

This week, I have learned the correct ways in soldering the components on the PCB board. Practice make perfect. If we want the best result in soldering, we must doing the work neatly and have high focusing in complete the circuit's soldering.