problems

These are common defects associated with soldering iron and involve the final result being solder-starved or having excess solder. These lead to instable joints, poor electrical connections and failure of components. We look at how the problems come to be and how to solve them.

Excess solder

Excess solder on the other hand occurs when too much solder is applied on a component lead or pad or both. This usually results in an almost spherical ball of solder. The downside to excess solder is that in most instances, wetting is very poor with the lead and pad and may therefore lead to a very poor electrical connection.

Solder starving

In soldering, a solder-starved joint is the point of a bond formed by molten solder that did not receive as much solder as required. Solder starved joints can be caused by a wide range of factors including incorrect soldering temperatures, poor contact between the solder and iron tip and use of poor quality solder. A solder-starved joint often develops cracks with time, forms poor bonding of components and is thus generally unreliable as a contact point especially in soldered electrical components. There are however easy solutions to these problems. These include:

Desoldering and resoldering

For excess solder, the easiest solution is to desolder the joint and remove all the solder. After this, redo the soldering taking care to feed just the right amount of solder into the joint. The end result should be a symmetrical concave shaped mound of solder that is even on all sides. For a solder-starved joint, desoldering may not be necessary since all that is needed is the application of additional solder on the joint. It however takes a bit of time, practice and a few mistakes to make the perfect solder joint.

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soldering iron

Soldering irons can be classified by various means. However, let us look at the types depending on the features that the iron has. We can have those with interchangeable or fixed tips, thermostat-equipped or without, those with user interface screens and the ones without.

Fixed and interchangeable tip

Some soldering irons only use a single fixed tip while others give you the ability to change the tip depending on the particular task at hand. The interchangeable tip iron variety makes use of a tip kit. A good soldering iron should have a tip kit containing at least three kits. These should vary in shape and size from sharp to chisel-shaped. The varied tips will come in hand in carrying out unrelated soldering tips with the sharper ones being used for tasks that require high precision. Attractive alternatives in the market come with a five-tip kit.

Fixed-temperature and thermostat-equipped

A good soldering iron should also have an inbuilt temperature control thermostat to adjust the heat output depending on specific soldering needs. Some soldering irons adjust the heat automatically depending on the solder and surface while others use a fixed heat level. However, it is best to have control over the heat while working with a soldering iron thus the preference for those with inbuilt controls. This could also affect how fast the iron heats thus making it even more appealing to have the ability to exert control over this.

Digital and analogue soldering irons

A digital soldering kit exceeds the regular soldering kit on various fronts. These include having a microprocessor-controlled temperature, LED displays, automated power-off functions and memory mechanisms. The display serves as the user interface and allows the operator to input parameters that include temperature, time and other usage aspects. Digital kits have become much more common than they were a few years ago.

 

 

 

 

 

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tools

Solder is basically an alloy wire that melts at relatively low temperatures and therefore flows and forms bonds between metals. We look at the most common solder materials (alloys) available in the market.

Lead-Tin alloy (60-40)

Solder, in its most basic form is usually a metal alloy wire with a relatively low melting point that flows to form bonds and seal joints in other metals. There are various types of solder that exhibit different characteristics in terms of liquidus, solidus, and composition, tensile and sheer strength. The 60-40 type of solder is basically a metal alloy containing 60% lead and 40% tin. This used to be the most common type of solder but this is gradually changing due to the strict regulations governing the use of lead. Lead is known to have a very low melting point and thus a larger proportion of lead in the alloy will cause it to have a lower melting point.

Tin-silver-copper

After the enforcement of anti-Lead regulations, most manufacturers changed to this alloy as a replacement. The tin silver copper alloy is used by more than two thirds of manufacturers in Japan. Like the 60-40 alloy, this alloy has a very low melting point though not as low as that of lead-tin alloy.

Zinc alloys

Zinc is a natural chemical element often found in the earth’s crust and in varying concentrations within its mining areas. In soldering, zinc is widely used in the soldering of various items. However, this is usually done using zinc-based alloys and not the element in its pure form. Due to its relatively high liquidus, it’s often necessary to use an alloy based on zinc and a metal with much lower liquidus. Common metals to form the alloy include cadmium, tin, lead and copper.

 

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solder

These are common defects associated with soldering iron and involve the final result being solder-starved or having excess solder. These lead to instable joints, poor electrical connections and failure of components. We look at how the problems come to be and how to solve them.

Excess solder

Excess solder on the other hand occurs when too much solder is applied on a component lead or pad or both. This usually results in an almost spherical ball of solder. The downside to excess solder is that in most instances, wetting is very poor with the lead and pad and may therefore lead to a very poor electrical connection.

Solder starving

In soldering, a solder-starved joint is the point of a bond formed by molten solder that did not receive as much solder as required. Solder starved joints can be caused by a wide range of factors including incorrect soldering temperatures, poor contact between the solder and iron tip and use of poor quality solder. A solder-starved joint often develops cracks with time, forms poor bonding of components and is thus generally unreliable as a contact point especially in soldered electrical components. There are however easy solutions to these problems. These include:

Desoldering and resoldering

For excess solder, the easiest solution is to desolder the joint and remove all the solder. After this, redo the soldering taking care to feed just the right amount of solder into the joint. The end result should be a symmetrical concave shaped mound of solder that is even on all sides. For a solder-starved joint, desoldering may not be necessary since all that is needed is the application of additional solder on the joint. It however takes a bit of time, practice and a few mistakes to make the perfect solder joint.

Read more