CONTRACT MANUFACTURING Figure 1: Laserssel Facility
Selective Reflow Technology overcomes complex design challenges
Brian Sohn discusses how Laserssel’s laser selective reflow technology revolutionises functionality and performance of next-generation electronic devices
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aserssel Corporation is a pioneer in selective soldering segments (figure 1). The company has provided customers with unique soldering capabilities to allow soldering on heat-sensitive substrates that once were considered impossible to reflow. Since being founded in 2015, Laserssel offers advanced packaging, plastic and organic substrates, very thin substrates with concern of warpage and any other challenges that were difficult, if not impossible, using the conventional reflow process.
With R&D beginning almost 12 years ago, Laserssel has come a long way, growing and strengthening its reputation. In 2015, it founded CrucialMachines, became a registered technology laboratory, participated in the government-sponsored project “Development of Non Conductive Film (NCF) for Stated Package of TSV 3D IC” and developed laser selective reflow (LSR) with a 50x50mm laser beam. One year later, it completed the reliability of LSR with the AREA consortium in the United States, was chosen as a global IP company and registered as a venture company. Growth continued and, in 2017, Laserssel became ISO9001 certified, set up sales channels in Asia, began delivering LSR to electric vehicle and semiconductor customers, and
38 JULY/AUGUST 2021 | ELECTRONICS TODAY
developed compression LSR. 2018 was a pivotal year as the company was selected for the GlobalStar venture program “Development of Multi Beam Large Area Laser Reflow System for High-Efficiency Production of Advanced Flip Chip Semiconductors.” Also that year, the company completed the MP version of in-line compression LSR(LCB) and launched the Laserssel brand. The next year showed continued growth with the company setting up sales channels and CS partners in the United States, being selected as an Inno- Biz company and setting up LSR in the global top tier semiconductor foundry. In 2020, Laserssel was selected as a PPURI Technology Specialised company, participated in two technology development government projects and launched the rLSR mini LED application, a Laser rework solution of tiny LED on BLU substrate. It also won the 2020 Korean Venture of the Year Award from the Ministry of SME and Startups. Laser Selective Reflow (LSR) is the mainstay of Laserssel (Figure 2). The company created the technology to deliver a uniform defocused laser beam over a specifically tailored area on a printed circuit board (PCB). The uniform defocused beam is controlled and delivered to the product via the Beam Shaping Optic Module system (BSOM) on a
user-defined area. This unique feature permits users to implement novel soldering solutions not possible with past techniques. It also allows the selective application of energy to locations that require soldering while not heating up potential thermally- sensitive areas. Additionally, LSR is potentially a means to mitigate or even eliminate the warpage of various packages. It provides an extremely reliable, fast (only 1-3 second laser bonding per selected area) bonding process. Laserssel developed the technology by using a distinctive recipe and a highly uniform optic system.
LSR provides numerous advantages including few seconds ramp up, 65°C per second cooling rate, uses focused heat only on selective area heating, requires no PCB elongation on smaller warpage, takes up less floor space (no 5-10 step temperature zone required) and saves energy because it does not require the 10-30 min/hour N2 purge. Additionally, while mass reflow heats up the entire atmosphere, LSR only heats areas where soldering takes place, resulting in minimum damage to substrates that pass through reflow. Other benefits include fast tact time and BSOM beam uniformity. LSR also offers high reliability. For fine-pitch/ semiconductor, it provides 40 micron pitch
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