Welding is used in all types of repairs of machinery or molds. It’s cheaper and saves time to weld rather than make a new part or parts from a mold. What may surprise you, however, is that there are different types of welding, depending on your needs.
What is micro welding? Micro welding is an arc welding process done at extremely low amperages, using a high powered microscope. It’s normally done on smaller, delicate components and the technician is essential to making the process complete successfully.
Micro welding is a state of the art process that is also referred to as precision welding. We’ll go into micro welding in more detail and explain other forms of welding in the paragraphs below.
What Is Micro Welding Used For?
Micro welding is anything smaller than the traditional welding process, even as small as .0003 inches. It uses tungsten inert gas (TIG) in welding equipment about the size of a pen.
Here’s a cool video demonstrating some of what it can do and what it’s used for.
It’s a tricky operation since often micro welding requires the surrounding area to be unaffected by the heat. Technicians use powerful microscopes to see the tiny arc and to obtain the precision they need. It calls for extreme concentration. The mechanics of it are as follows:
- Electric current is passed through tungsten electrode to grounded work pieces, creating heat
- Argon or helium gas used to form an arc and shield surrounding area from contaminants
- Heat is generated at point of arc gap
- Molten pool is established
- Filler rod introduced into molten pool
Micro welding can be used on almost anything, including:
- Stainless steel
Brass and galvanized steel are not great for micro welding. The zinc content can cause welding issues.
Imagine you work in a specialized machine shop and a customized tool has just broken. A great way to fuse that back together is micro welding. This is a real advantage over having to remake a piece and only one of the many uses for micro welding.
Engineers use dies, which are specialized tools to cut or shape other material. Some of these are small and intricate, so when they are damaged, micro welding is one way to salvage the die, preventing serious downtime in any industry. It takes far less time to micro weld and repair a customized tool than it does to produce an entirely new tool.
For batteries, you can weld tabs to terminals. For automotive, you can weld PCB tabs together. The list of items you can micro weld is almost endless. Basically, if it’s metal (except for aluminum) you can micro weld it.
What Is Pulsed Micro TIG Welding?
Micro welding evolved from traditional TIG welding, with the difference being that micro welding uses extremely low amps, usually less than 10. One type of micro TIG welding is pulsed TIG welding. The current can run up to 300 amps but is generally much lower than that. Pulse durations generally last up to 4 seconds and have a plasma discharge. Pulse welding features a power supply with a non-consumable electrode.
Pulse welding is generally an edge welding process. As the tungsten electrode is withdrawn from the weld surface, the melting process starts from the outside and penetrates inwardly. Pulse welding can be used to add additional material, like fill wire, or you can melt and fuse parts together without the need for fill wire.
Micro TIG welding is especially good for these industries:
Pulsed arc welding or micro welding has these advantages:
- Solder-free process
- Highly durable weld
- Can join high melting point metals or dissimilar metals
Micro TIG welding hasn’t been around that long. It was only invented a little over 50 years ago.
What Is Fine Spot Micro Resistance Welding?
Resistance welding joins two metals together. It generates friction heat when force is applied and uses that heat for welding. In resistance welding, a welding head holds the metal between a positive and negative electrode and applies pressure. A welding power supply applies electric current to the metal to be welded. The current melts the metal after pressure has been applied.
Fine spot welding does not need specialized technicians to run the process. Spot welders can also be relatively inexpensive, and you can get a DIY kit from several companies, including this one from Causin (check it here on Amazon). Of course, fully prepared spot welding kits can be much more expensive, costing upwards of $200.
Spot welding is performed at a very low voltage with a very high current. The pulse timing is critical, and a perfect weld is timed down to the millisecond. It is the most widely used resistance welding method. The main reason for spot welding is to join two or more light gauge overlapping metal sheets.
The technique for resistance spot welding is as follows:
- Clean the metal sheets you want to weld together
- Make sure the electrodes are also clean
- Use two copper electrodes at the same time for clamping the metal sheets together
- Let the current pass through the electrodes into the metal sheets
- The generated heat will melt the metal sheets at the desired spot
This process works so well because the copper is an excellent conductor of heat while the metal is not. Because of this, the heat remains in one spot where the copper electrodes are touching and does not spread across the metal. The metal is melted at the correct spot and the joint between the sheets is formed.
The advantages of resistance spot welding are numerous:
- Low cost
- Doesn’t need highly skilled worker
- Warping of parts is eliminated (It does leave some indentation)
- Joint is highly uniform
- Can be done by automatic or semi-automatic operation
- Multiple pieces can be done in quick succession
Some disadvantages of this process are listed below:
- Equipment can be costly unless you make it yourself
- Some metals need special surface preparation
- Thick jobs are not easy to weld
Spot welding can be used for attaching braces or pads and can have a multitude of other uses. It is most commonly used in the automotive and aviation industries.
What Is Thermocompression Micro Welding?
Thermocompression welding, or bonding, creates a solid body diffusion between two objects, rather than a melting at the contact points. It requires a lot of force at a very high temperature to create a metallurgical bond between two surfaces. One of the most common bondings of this type is gold to aluminum.
Thermocompression welding requires a specially designed electrode to provide a high degree of precision to the welding zone. This is more precise than any other micro welding technique. The electrode bonds in such a way that the two halves to be welded can remain isolated. It allows for fine control welding and prevents damage to electrically sensitive components.
Unlike other types of welding processes, thermocompression welding creates no liquid phase. Instead, it relies on high temperatures and a long bond time of one to several hours. Temperatures for the bonding process should reach higher than 572F. The material to be bonded must be clean and must contain no scratches or particles that could cause air gaps.
Thermocompression welding is used most often between a bonding wire and a substrate metallization. The required heat is applied either by a heated capillary or by mounting the substrate on a heated stage. Most processes use some of both.
Metal to metal thermocompression welding provides some advantages:
- Enables hermitic seal
- Enables mechanical support
- Enables electrical contact
- No risk of structural degradation
- No risk of electrical short
- Offers good connection when soldering or welding is not possible
- Low heat input
- No melting
Higher temperatures and pressure can lead to higher toughness bonds. Thermocompression welding is a good process if you’re not using two very small materials. Where micro welding is used for precision jobs, thermocompression welding is used more for bonding larger items, such as metal sheets, together.
What Is Laser Welding?
While micro welding uses electric current to generate heat, laser welding uses light energy to rapidly heat the weld zone. Laser welding melts the filler rod along with the adjacent point of metal joining. The light energy intensity is controlled by:
- Beam size
- Pulse width
No current flows through the welding zone and there are no electrical connections to the weld. With micro welding and resistance welding, heat is generated in the work piece by electrical current flow. With laser welding, there’s simply a laser beam being used to melt the filler rod and base material. Microscopic magnification is used in both processes.
Laser welding requires a straight line of sight between the laser beam and the weld zone. If you don’t have a straight line of sight, the weld will not work efficiently. Laser welding is most often used in automated welding procedures.
Heat in laser welding is highly focused and does not affect the surrounding weld area. You can even complete the weld while holding the metal in a bare hand. This means even heat sensitive areas can be laser welded with little chance of damage.
Laser welding is used frequently in the automotive industry, in an automated fashion, to weld automotive parts together. However, it’s also used in jewelry and medical industries to put together metals on a more micro level.
Lasers are becoming the go-to welding method for many of these industries for the following reasons:
- Precision – this method offers a high level of control and accuracy
- Can create complicated joins – You can weld dissimilar materials and hard to reach areas
- Low heat application – Low heat minimizes component distortion as it results in less thermal strain being placed on the parts
Laser welding is relatively low cost and creates strong and reliable welds, allowing businesses to increase efficiency while keeping costs to a minimum.
Micro TIG Welding Versus Laser Welding
Both micro pulse welding and laser welding produce very strong welds. However, the way the welds are approached is quite different. Laser welding uses a light beam, while micro welding uses an electric current and an arc to fuse metals together. While laser welding can control both spot size and amount of energy that is discharged, micro TIG welding can only control the amount of energy. This means laser welding can give you a smaller weld spot size.
Here are the advantages of micro TIG welding:
- Allows deeper penetration, especially on silver. Laser welding is not great on silver
- Will only weld conductive materials – this is good when other materials are close to the weld area
- Can control energy to lower levels
The advantages of laser welding are:
- Can be used to smooth out and polish areas that have been welded together
- Does not require a grounding clip
- Can control weld spot size
Choosing between the two welding methods depends on the materials you are using, and the weld spot.
Difference Between Brazing, Soldering, And Welding
Welding is the art of joining two pieces of metal together. So is brazing. So is soldering. But what is the difference between these three processes and when should you choose one over the other?
- Brazing – Brazing involves the use of a filler metal to create a bond. It does not melt the base metals to make a join. It involves temperatures above 800 degrees.
- Soldering – This method is like brazing but uses a tin and lead alloy filler metal. It melts around 390 degrees.
- Welding – Uses a gas (often argon or argon/helium in micro welding) to create an arc and melt metal into a pool, creating a weld. Filler metal is added to the weld to help create a join.
Here’s when you should use the three methods:
- Brazing – Use to join dissimilar metals using a filler rod
- Soldering – Use to join electronic parts
- Micro TIG welding – Use to join similar metals at a very high temperature
Brazing and soldering do not create as strong of a weld as Micro TIG welding, but they are good for small, delicate parts.
The Science Behind Welding
Before TIG welding, most welding was done using a high intensity flame. It was messy and sparks could get anywhere. With the advent of TIG welding, an electrical arc creates the heat.
In TIG welding, you use a power supply to provide the energy. One lead acts as a “ground” and connects to the welding material. The other lead attaches to a handheld gun.
The welding gun has a conductive tip Ade out of tungsten. You quickly tap the tungsten tip to the base metal and then withdraw it just a bit to create an arc. An arc is formed when the electrons are ionized as the electricity tries to complete the circuit.
These arcs create a large amount of heat and light. The higher you push the amperage, or power supply, the higher the temperature of the arc.
You move the arc in a circular motion to create a weld pool of melting metal. As the two metal pieces melt, a fusion takes place, allowing the two metals to become one. Once the melt has started, filler is added separately, lending strength to the weld, and filling in any gaps between the two pieces.
The important thing to note is that the two metals being joined need to have a similar melting point. If they don’t, one metal will melt faster than the other metal and could result in a failed weld.
Here’s an easy to remember guide for Micro TIG welding:
- Arc – Creates the heat that fuels the melt
- Melt – Necessary to create the fusion for the metals
- Filler – A metal used to strengthen the join
- Shield – Arc welding requires a shield. TIG welding uses gases to contain other gases from contaminating the weld pool
- Cool – Some people use water to quench the heat, but it is recommended to let the weld cool down naturally
- Clean – Clean and smooth the weld, not only for appearance but to allow the coating to bond better
The Final Word
Blacksmiths invented welding by using heat and a hammer to fuse two metals together. In 1800, the electric arc was discovered, but it would be over 80 years before people started using it to join metal. As it was developed in the early 20th century, demand grew higher for this faster and more efficient method, leading to the developments we see in welding today.
The pros of arc welding are:
- Creates the strongest bond between two similar metals
- Cheaper and faster than bolting or riveting
- Can be automated in certain instances
- Stronger than trying to heat and mold two shapes
- Safety from the strong bond
Because of this, manufacturing and many other industries rely on Micro TIG welding for their production line. It creates safe, strong joins and micro welding can be used on the smallest components, and in an environment with other fragile components.
Micro welding equipment is small, so it’s easy to maneuver. Offering superior control while controlling the heat of the weld gives welders the freedom to weld small pieces that were previously considered to be a loss. This saves money and time for industry. It has also created a new industry in micro welding, with specialized shops cropping up all over the country.
Micro welding is here to stay, or at least until the next technological breakthrough happens.