Can Fiber Lasers be Used for Wire Bonding in Electronic Components?
Laser cutting, laser drilling, laser ablation – there are so many different processes that lasers can be applied to that sometimes it is difficult making out the wood from the trees. Here we will try to cut through all the mumbo jumbo, tech talk and general confusion to provide you with a clear description of what laser cutting really is, what it can achieve and some examples of where we can apply it. Next, we will provide a jargon buster to help you navigate through all the confusing tech-talk we sometimes come across.
Ultrasonic wire bonding
The most common joining technique in the semiconductor industry is ultrasonic bonding. This is a friction welding process that places the wire, and the connector terminal or pad in physical contact then uses an ultrasonic pulse to bond the two materials thermally. Ball bonding and wedge bonding are both used. In the former, the tip of the wire is momentarily melted to form a small ball a few times the diameter of the wire.
While the process is well established in the electronics industry, it can run into problems when used for high power devices. As these devices use high currents, thicker wires or ribbons must be used. A 500-micron wire will fuse at 35 amps, so for higher currents either thicker wires are needed, or multiple parallel connections must be made.
Problems bonding thick wires for high currents
Thicker wires and ribbons cause problems. It becomes increasingly difficult to clamp the parts together and apply enough ultrasonic energy to form a reliable bond. This is even more problematic when connecting lithium-ion battery cells that can deliver currents of around 45 amps.
This is where fiber laser wire bonding steps in. By combining a standard wire bonder with a fiber laser, high-quality connections can be made between the bond pad and the wire ribbon. The wire bonder tool holds the wire ribbon and the bond pad together, and the laser spot is focused on the bond ribbon, close to the device forming a weld between the ribbon and the pad. Similar processes are also used for bonding Micro-Electro-Mechanical Systems (MEMS).
Laser Impulse metal Bonding
Laser Impulse metal Bonding (LIMBO) is an alternative process for connecting heat sensitive components. This process maintains a gap between the bonding ribbon and the device connector pad. The laser pulse heats the ribbon without heating the device, forming a melt pool. The pad and ribbon are then brought into contact, creating the join.
Further information from SPI Lasers
This is just an example of how fiber lasers are contributing to leading-edge manufacturing processes. If you would like to discover more or talk to us about how fiber laser technology might impact on your sector, please feel free to contact us.
Image Credit: Htomari
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