Overview of Welding Semiconductors
Semiconductors are the backbone of virtually all modern technology. If electricity flows through it, there are semiconductors in it: diodes, transistors, integrated circuits, chips and all types of microelectronic assemblies. Things as seemingly simple as the lights in our houses are semiconductor driven.
Critical to the assembly of these ubiquitous devices is welding. Further, critical to the manufacturing of semiconductors are the machines themselves. Semiconductor manufacturing relies on chemical compounds that can be highly reactive and toxic. Welds in semiconductor manufacturing machinery are typically demanding.
Whether on the part itself or the machine making the part, the semiconductor industry demands welds that evince high levels of accuracy and precision. The joins involved can be miniature in scale, measured in nanometers, but can also be on much larger assemblies used in the chip manufacturing machines themselves. Further, the welded connections made must have high reliability and strength to withstand whatever stresses the semiconductor will encounter in its service life, or the machine will undergo during countless duty cycles.
Semiconductor Welding Processes
There are several types of welding used in the semiconductor industry, each with its advantages and disadvantages. The most common types include resistance welding, TIG welding, laser welding and electron beam welding.
Resistance Welding Semiconductors
Resistance welding is widely in the semiconductor industry. The process involves passing an electric current through the materials being joined and, due to resistance, heat is generated, melting the materials and fusing them. This method can be efficient and can produce an adequate weld. However, it is limited to certain types of materials, and the process and resultant welds can be negatively affected by contamination and oxidation.
TIG Welding Semiconductors
Tungsten Inert Gas (TIG) welding is also commonly used in the semiconductor industry. This type of welding uses a tungsten electrode to produce an electric arc, which melts the metal being welded. To get the required precision, the process is generally automated, and Orbital TIG welding is commonly employed on tubes and other elements because it is fast, precise and the resultant welds are high quality. Similar to resistance welding, TIG welding has limitations in terms of materials that it can weld. TIG welding’s big limitation has to do with imparted heat: TIG welding is a very high heat process and often the components on semiconductor assemblies are too sensitive/delicate and cannot be TIG welded.
Laser Welding Semiconductors
Laser welding is commonly used for joining semiconductors and it is an excellent process that creates strong, pure welds. Basically, a highly focused, coherent beam of light is directed at the weld joint and it simply melts the materials involved. The very nature of a laser allows for extreme precision in terms of weld placement and energy input, and the process lends itself to automation. Unlike resistance and TIG, lasers can join the wide variety of materials utilized in semiconductor manufacture, making it very versatile.
Electron Beam Welding Semiconductors
Electron beam (EB) welding uses a focused beam of accelerated electrons to heat the materials to their melting point and join them. EB welding is capable of welding materials that traditional methods, and even lasers, struggle with, such as Copper. Electron beam welding is typically automated and is capable of incredible precision and repeatability. The welds produced are strong and extremely pure, as the EB process must occur in a vacuum—the presence of air or any gases causes scattering of the beam. The need for a vacuum chamber is one of the downsides of electron beam welding, which requires pumping down the chamber at the start of each welding cycle to achieve the requisite vacuum. However, a carefully developed welding methodology and proper tooling can make EB welding very cost effective. Perhaps the biggest downside to EB welding is the expense of setting up a system. The machines involved are expensive and require trained operators and thorough maintenance. Electron beam welding isn’t something that can be approached casually.
Semiconductor Welding Process Comparisons
The following table compares the various types of welding processes. Please note that the specifics of an application determine the best joining process.
|Process Speed||moderate||moderate||very fast||fast|
|Heat Input||moderate||very high||low||low|
|Joint fit-up Tolerances||low||low||high||high|
|Weld Penetration||low||moderate||high||very high|
|Range of Dissimilar Materials||narrow||narrow||wide||very wide|
|Controllability||fair||fair||very good||very good|
|Ease of Automation||excellent||good||excellent||moderate|
Guidelines for Semiconductor Handling during Welding
The components involved in semiconductor manufacturing are typically small and delicate, and require careful storage, handling and processing to prevent contamination and ensure high quality welds. This includes using cleanroom environments, ultrasonic cleaning, protective coatings and trained personnel at every step of the process. Larger assemblies require an additional level of care so that no components are damaged during handling. The materials involved in semiconductor components and assemblies can oxidize quickly if not handled with the necessary level of caution and stored correctly. Experience and properly developed procedures can make or break a semiconductor assembly during welding.
EB Industries has designed our business around welding and testing processes that essentially eliminate the chances of a weld damaging circuits and components. Our processes meet the standards of ISO 9001:2015/AS9100D, MIL-SPEC 45208A, NADCAP and ISO 13485. We’re also certified to propriety standards by companies such as Raytheon, Pratt and Whitney, and others. For a complete list, see our industry certifications page here.
Semiconductor welding is the linchpin of modern technology, underpinning everything from household gadgets to advanced microelectronics. And paramount to the manufacturing of the electronics in these devices is precision and reliability.
Resistance welding, using electrical resistance to generate heat and fuse materials, can be highly efficient but is limited by material compatibility. TIG welding, utilizing electric arcs, can be automated and is capable of pure, precise welds but also has material restrictions.
Laser welding, employing a focused coherent beam of light to melt materials, offers unmatched precision and adaptability across a spectrum of materials, as well as excellent automation capabilities. Finally, electron beam welding, utilizing accelerated electrons in a vacuum chamber, achieves unparalleled purity of welds along with tremendous precision and repeatability, and can weld most materials, including challenging, exotic metals and hard to weld dissimilar metals. However, EB welding requires extensive set-up and maintenance.
A completed weld is only as good as the preparation process, the care and quality commitment of the welding operators and support staff. And as components and devices continue to increase in complexity and ubiquity, innovation and quality will remain essential.