High-precision welding is important in many industries — especially sectors like semiconductors, electronics, and telecommunications — that rely on the ability to process precise features and paths on delicate devices. The techniques up to this challenge are resistance welding and laser welding, the more traditional choice, followed by the newcomer gradually taking over the scene. Laser technology has gained in popularity in recent years because of its ability to accurately deliver heat to a very small area without damaging the material around it and avoiding tool wear and tear. On the other hand, resistance welding is still widely used because it is perceived as better suited for fabricating larger volumes.
The importance of control
One thing that is crucial to both welding techniques is control. A uniform weld relies on the same energy being consistently applied to the whole path, and, if this fails, it can create heat-affected zones that break easily or gaps in the weld. This means that laser power, firing time, and position all need to be carefully controlled and monitored.
Creating a uniform weld when the path is straight is relatively simple, but when it is curved or has corners, it can be tricky. When moving in a straight line with the same speed, the two velocity components x and y remain constant, but they will change when turning, even if the total velocity is still constant. This effect needs to be considered by the laser, adjusting either the frequency or the power to deliver the same result to the whole path. This increases demand either on the welding instrument itself or on the positioning tool since both need to work together to achieve excellent results. For example, YAG lasers can be held at a fixed spot, with the motion stages responsible for moving the product along the desired path. There is also an option to use a continuous wave (CW) laser with a galvanometer head that works in unison with the motion stages to correctly position the product.
Purpose-designed control systems, such as those developed by ACS (a PI motion control company), can give users far more flexibility in how they build and then repurpose set-ups. Even tiny changes to a fixed configuration can be complex and time-consuming if each of the different parts needs to be programmed separately and, until recently, it has been common for companies to have one set-up made for each specific task. However, newer controllers that connect the motion stages and the laser pulsing hardware through EtherCAT make it far more straightforward to change an existing build. This flexibility also reduces the complexity of drives that are needed and so cuts costs.
Anything that can reduce costs this way is quite welcome in the highly competitive laser welding market. Making a high throughput process automatic can also help; Industry 4.0. is all about using machine-machine communication — either directly or wirelessly — to automate the manufacturing procedure, and several companies have already started to adopt this approach for quality control purposes.
For the same reason, less expensive components are now available and can make a significant difference to overall costs. Not every application needs every component to be at the highest possible specification; for example, for some tasks, lower specification stages — such as the new L-812 range from Physik Instrumente (PI) — are significantly cheaper than high-end stages but still provide accurate motion control. Similarly, finding a supplier with the expertise to build a system around your application can be a very cost-effective approach. For example, the UK company Pyramid Engineering specializes in the final sealing of electronics packages. It offers its clients expertise in combining the very best hardware components with control and automation to sharpen up processes and deal with high throughputs.
High-precision laser welding has carved a niche into many industries where processing precise and complex features is a routine and sometimes high throughput requirement. Control is key for quality, and the choice of systems and hardware components for system builds can have a significant effect on overall manufacturing and running costs. New developments continue to bring cheaper — but still high-quality — options into this competitive marketplace, giving users more flexibility and carving out even more potential applications for laser welding.
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