Last Updated on October 22, 2023 by Kevin Chen
When it comes to electronics manufacturing, manufacturers are faced with a number of challenges. In order to meet consumer demand for smaller and more efficient devices, manufacturers must be able to create solutions that are smaller and more compact than ever before. This is where wire bonding comes into play.
This manufacturing process is commonly used in electronic devices to connect different components such as semiconductors (e.g. chips) and printed circuit boards (PCBs).
Wire bonding is an effective way to create strong connections between different components while also keeping their individual sizes small.
In this blog post, we’ll cover everything you need to know about wire bonding, including examples of its use, the equipment used during the process, and a list of potential risks when using it as part of your manufacturing processes.
What is Wire Bonding?
Wire bonding is a manufacturing process that connects two pieces of metal using a wire to create a connection. More specifically, two pieces of metal are bonded together with a wire that is then heated to create a joint. This joint will then remain in place (with some type of adhesive) after the wire is removed.
This joint can then be used to connect a chip to a circuit board, for example. Wire bonding is often used in electronic devices, such as computer chips, batteries, and other circuit boards.
To create a connection between two pieces of metal as part of a larger device, manufacturers will use a wire to connect them together. The wire is then removed, leaving a bond that can remain in place. These bonds are strong and reliable, making them an ideal way to connect components together.
What Does Wire Bonding Do?
Wire bonding is used to create a strong connection between circuit boards, chips, or other electronic components.
For example, during the production process for computer chips, manufacturers will use wire bonding to connect a chip to a circuit board. The two pieces of metal are connected together using a wire, which is then heated to form a bond.
The bond created through this process is strong and reliable, making it a viable option for connecting components together.
How Does Wire Bonding Work?
During the wire bonding process, two pieces of metal are connected using a wire. The thickness of the wire will vary depending on the components being connected and the application. For example, in the computer chip production process, a thinner wire is used to link a chip to a circuit board.
The wire is then heated with an electrical current, which melts the wire. This creates a bond between the two pieces of metal that remains once the wire is removed. The strength of the bond will vary depending on the current being used to heat the wire.
Wire bonding process: Steps
There are a few different ways to conduct a wire bonding process, depending on the components being connected and the needs of the manufacturer. The steps outlined below are one of the most common processes used during wire bonding in the manufacturing industry.
– Pre-Bonding Phase
This phase of the process begins with cleaning the surfaces that will be connected together. The surfaces must be free of debris and particles to ensure a strong bond. This phase also includes assembling the components that will be connected together.
– Bending Phase
Next, the wires are bent around the components being connected. These bends will be used to create a connection between the components once the wires are heated.
Bending is done using a wire bending machine that uses a wire-bending mandrel. The mandrel is heated to soften the metal and allow it to be shaped around the components being connected.
– Pre-Tinning Phase
Tinning is the process of coating the wire with a thin layer of solder to prevent oxidation during the bonding process. This phase also includes cleaning and preparing the surfaces that will be soldered together.
– Bonding Phase
After the wires are pre-heated, they are applied to the metal surfaces that will be connected together. The wires may be applied manually or with the assistance of a machine. The current applied to the wires will vary depending on the metal being bonded. – Post-Bonding Phase- Once the wires are applied to the metal, they are heated using an electrical current. This electrical current is higher than what is used to pre-heat the wires. This high current melts the wires, which creates a bond between the two pieces of metal.
After the wires are bonded, they are tested to ensure that the connection is secure. This phase also includes cleaning and preparing the surfaces that will be soldered together. Various equipment is used to test the wires and ensure that they are secure.
Examples of Wire Bonding
Let’s look at some of the real-life examples of the wire bonding process:
-Copper wire bonding: This type of wire bonding is commonly used to connect an IC chip to a printed circuit board. The metal being bonded together in this example is copper. The bonding process involves applying the heated wires to the metal surfaces and then melting them together with a high current.
-Precious metal wire bonding: This type of wire bonding is used for high-quality applications, such as medical devices and aerospace parts. It consists of heating the wires, which are made from gold or silver, prior to applying them to the metal surfaces. This pre-heating process protects precious metals from oxidation during the bond process.
-Gold wire bonding: Some PCBs and even IC are heavily characterized by gold metal. The reason for this is that gold is a highly conductive metal that can be easily applied to the PCB. The gold wire bonding process involves applying the heated wires to the metal surfaces and then melting them together with a high current.
-Aluminum wire bonding: This type of wire bonding is used when you need to create a bond between aluminum and another metal, such as copper or gold. The pre-heating process of this type of wire bonding involves heating it prior to applying it to the metal surfaces.
Temperature management for the wire bonding
The most challenging part of using wire bonding in your electronic project is getting the right temperature when melting the wires together. If you melt them at too low a temperature, they will not bond properly. If you melt them at too high a temperature, they will burn or oxidize (depending on what metals are being bonded).
The proper temperature for any given bond depends on several factors:
1) The thickness of the wires being bonded
2) The metals being bonded
3) The purity level of each metal
4) The amount of heat being applied
Once you consider these factors, you can calculate the correct temperature for your wire bonding process. The good news is most modern equipment will allow you to optimize these variables automatically. They also let you select the right temperature requirements for the bonding process.
Equipment Used During The Process
The equipment used during the wire bonding process varies depending on the manufacturer and the specific application. However, there are a few pieces of equipment that are common in the industry, including:
– Bonding heads- These machines are designed to connect two pieces of metal together using a wire. They can be used to connect components that are placed in close proximity or that are positioned far apart. The heads come in a variety of sizes, and they can handle a wide range of wire diameters.
– Dicing heads- These machines are similar to bonding heads, but they are used to cut wires. They are used in conjunction with a dicing blade or guillotine. This allows technicians to cut the wires at specific lengths and locations.
– Wire feeders- These machines are designed to feed the wire into the bonding head or dicer. They use a motorized spool that feeds wire through a tube, which is connected to the bonding head or dicer.
– Cameras- These pieces of equipment are used to capture images of the bonding process. They can be used for inspection purposes or quality control purposes.
– Process controllers- This is an electrical device that monitors and controls all aspects of the wire bond process automatically. It monitors everything from temperature levels to data collection and analysis during the process.
– Bonding fixtures- These fixtures are used to hold the components being connected. They help to keep the components in place during the process and help manufacturers create consistent connections between the components.
– Bonding ovens- These ovens are used to pre-heat the wires used during the bonding process. They are often used to pre-heat thicker wires that take longer to heat.
-Bonding press- The bond press is used to apply pressure to the bond head and the components being bonded together. It applies pressure with a tool called a slug, which is attached to a ram. The slug applies force to the components as they are pressed together by the ram.
Provides a high-quality and reliable product.
Benefits of Wire Bonding
– Strong connection- The bond created through the wire bonding process is strong and reliable. This makes it an ideal option for connecting components together in an electronic device.
– Minimal impact on size- The components being connected together through the wire bonding process will likely not be impacted by the size of the wire being used. The size of the wire will be small enough to fit between the components while still creating a strong connection.
– Simple and quick process- The wire bonding process is simple and quick, making it an ideal solution for manufacturers. The process can be completed relatively quickly, providing a viable option for connecting components together without slowing down the overall manufacturing process.
– Versatile process- The wire bonding process is versatile, making it a viable option for a variety of different components. It can be used to connect components that are placed closely together and far apart.
-Provides a high-quality and reliable product: Wire bonding is a very reliable way to connect components together. The process creates a strong and durable bond that will not be easily broken or disconnected.
– Cost effective: The wire bonding process is cost effective. It can be completed relatively quickly, making it a viable option for manufacturers looking to create a high-quality product at an affordable price.
-Allows for a variety of connections: The wire bonding process allows for a variety of different connections to be made. It can be used to connect components that are placed closely together and far apart.
Cons of Wire Bonding
– Affected by size- The bond created through the wire bonding process may be impacted by the size of the wires being used. For example, thicker wires will impact the size of the bond, making it less viable in some situations.
– Affected by materials- The materials being used will also impact the bond created through the wire bonding process. Materials with high thermal conductivity are more likely to be impacted.
– Risk of contamination- The wire used during the bonding process will remain in the bond after the process is completed. This means that contaminants present during the process may be in the bond as well.
– Risk of damage- The materials being connected together through the wire bonding process may be impacted. For example, if the wire is applied too closely to one of the components, it may damage it.
Classes of wire bonding
Wire bonding is divided into different classes namely, Ball bonding, Wedge bonding, and Compliant bonding. What are they and what’s the difference between them?
Ball bonding refers to a process wherein a metal ball is placed against the component and the wire is then pressed into the ball. The size of the ball varies from 0.5mm to 2mm. This bonding is mainly used on copper and gold wires.
Wedge bonding refers to a process wherein a metal wedge is pressed against the component, and the wire is then inserted into it.
The wedge used in this process has a thickness of 0.5mm to 5mm, while compliant bonding refers to a process wherein compliant material with high tensile strength is applied on top of the component, and then the wire is inserted into it through an opening in this material.
What are the different types of bonding techniques?
There are different methods or techniques used for wire bonding. Some are used in specific applications and not in others. Let’s look at some of these techniques and you will know which one you should use;
This technique is used in most applications and it is the most common method used. It is also known as thermal welding, and it uses a combination of heat and pressure to join the two components together.
The bonding process uses a hot wire that is heated to a high temperature. The hot wire then makes contact with the two surfaces to be joined and then pressed together for a short time period. This technique is easy to use, but it does have its drawbacks.
One of these drawbacks is that it can be difficult to control the temperature of the wire, which can lead to overheating or burning of components.
Another drawback of this technique is that there will be some resistance during the bonding process; this resistance may cause damage if not properly controlled, which will lead to problems in future applications.
Electronic bonding uses electrical current instead of heat to create bonds between two parts. This process uses an electronic circuit board along with an electronic device that has connections on its surface called bond pads or bond points which are connected through wires or conductors (usually copper).
These two devices are connected together through an electrical current created by three wires, one positive (+) and two negative (-).
When these devices are connected together through this circuit board, the current creates a strong bond between them; however, this bond will only last for a short amount of time before breaking down due to any external factors such as vibration or shock from other electrical sources like motors, etc.
Field-effect bonding is the most common method of electronic bonding. It uses a special kind of semiconductor called a field-effect transistor (FET) that changes the current flow on either side of it.
The FET, which is usually made of silicon, has two terminals: one terminal is called the gate and the other terminal is called the source.
The gate and source terminals are connected together through wires or conductors to create an electrical current that will pass through both devices being bonded, which will cause them to bond together.
Chemical wire bonding
Chemical wire bonding is a method that uses chemical reactions to create the bond. The two wires are heated together and then placed into contact with a solution that is usually made of an acid or alkaline liquid. This causes the two chips to bond together through a chemical reaction that creates an electrical connection between them.
Wire bonding reliability
Are these bonds reliable? You may wonder. Reliability in this context refers to how long the wire bonds will last. How long these wires will last is determined by the temperature of the two chips. If the temperature is high enough, the bonds can break down, therefore making them unreliable.
Wire bond reliability is a major issue that should attract your attention. This is because if the bond is unreliable, it will affect the overall performance of the electronic and PCB.
Manufacturers put in various measures to preserve the reliability of a wire bond. For instance, they will make the bond in a special way, or they will use special materials.
As a buyer, how can I tell that the wire bonding is reliable? Here are some tips:
-Look for the number of bondings. The more times the bondings are made, the more reliable it is. Also, you should look at the materials used in making wire bonds. If they have high-grade materials, like gold, silver, or platinum, then they will be more reliable than those with low-grade materials like copper, tin, and nickel.
-Look at the temperature coefficient of resistance (TCR). This is a measure to determine how much a material changes its resistance when it is heated up to a certain temperature range. High-quality wire bonds will have low TCR value (such as 1×10) while low-quality ones will have high TCR value (such as 10×10).
– Is there any damage on the wire? If you find any damage on the wire bondings (like burn marks or broken spots), that means that these wires have been damaged during production and subsequent testing so they will not last long even if they are properly used and maintained.
– Is the wire color consistent? The wire should have the same color throughout its length. If it is not consistent, then this means that there are multiple production lines in the factory and they are not taken care of properly which will lead to quality problems.
Choosing a wire bonding manufacturer
You don’t want to go through all the stress of wire bonding? You can always consider purchasing a pre-made wire bonding system that is already made by a trusted manufacturer and you can just plug it into your machine.
You don’t have to worry about the quality of the material or the wire because it has already been tested and certified by a trusted manufacturer.
You can also ask your manufacturer to provide you with a quality assurance report that will show the quality of the wire and its production process. This will give you peace of mind when it comes to using their products.
If you don’t know where to find these manufacturers, you can always get a sourcing agent to do the work for you. A reliable agent such as ICRFQ has the contacts of all the wire bonding experts in China.
If you want to find more Electronic Components Distributors, please check out the following articles:
- The Art of Sourcing: How We Identify and Partner with Top IC Manufacturers - November 24, 2023
- Essential Electronics Test Equipment You Should Know About - November 24, 2023
- How To Finish PCBA Design Process Quickly? - November 24, 2023