Photonic Soldering - New Materials and Applications

Photonic Soldering — New Applications and Materials Innovation

In electronics assembly, conventional wisdom states that all components and materials on the PCB must be able to withstand the reflow temperature of the solder alloy. The reason for this is simple: thermal damage during component attachment can hurt product reliability or prevent a product from functioning altogether. However, this creates some tough bargains for product designers. Oftentimes, key aspects of a PCB design are determined by maximum temperature constraints during assembly, rather than the intended use and performance of the product.
Photonic soldering technology from PulseForge circumvents this issue, making it possible to assemble temperature-sensitive components with a wide range of solder alloys. With low-temperature materials back on the table, there are more possibilities than ever for exciting new products and substantial improvements to existing designs.
Photonic soldering makes this possible with extremely rapid heating over extremely short time scales. Heating occurs via optical absorption of intense white light at the top surface of the PCB. The heating rate is fast — much faster than the rate of heat conduction throughout the PCB. This results in a local build-up of heat within the solder paste, so that reflow begins and ends before the temperature ever has a chance to equalize throughout the PCB composition. And because the heating is localized, the total thermal energy delivered by photonic soldering is small — just enough to reflow small quantities of solder, and not enough to damage components.

Thermally Sensitive Components

Having a self-contained power supply has become a standard requirement for many new products, from consumer electronics, wearables, and IoT, to industrial sensors and medical devices. However, most consumer-grade batteries suffer performance degradation when exposed to high temperatures. Since they cannot be soldered directly to PCBs using oven reflow, batteries are typically accommodated using mechanical clips and headers added to the PCB layout. Of course, these accommodations increase PCB cost and size, and add extra steps to assembly.

Now, however, direct soldering of tabbed batteries is possible with photonic soldering. Similarly, temperature-sensitive sensors and other specialized components can also be attached using a wide range of solder alloys. In addition, photonic soldering allows flexible cables and wires to be soldered directly to circuit boards and other components without the traditional headers and connectors, further reducing product size, weight, and cost.

Thermally Sensitive Substrates

Low-temperature substrate materials are another exciting possibility for PCBs assembled with photonic soldering. This includes a diverse range of plastics, 3D-printed materials, recycled materials, paper, fabric, and glass. The range of possible benefits are equally diverse — weight reduction, cost, optical transparency, recyclability, and mechanical flexibility are just a few of the most compelling examples.
Mechanical flexibility, in particular, is worth a closer look. Flexible film substrates, such as polyimide, enable the functionality of a PCB to be integrated into the form of a product. The resulting space and weight savings, not to mention the aesthetic benefits, find wide applicability in consumer electronics, wearables, lighting, and numerous automotive, aerospace, industrial, and medical applications.
Photonic soldering makes it possible to assemble circuits on many types of flexible substrates that cannot survive conventional reflow processes. One particularly useful example is PET, the same plastic used to make soft drink bottles and rigid food packaging. As a thermoplastic, PET is easy to form and process, and can be recycled. PET is strong for its weight, and optically transparent, which makes it especially appealing for lighting applications.

Ultimately, PCB design benefits from having a diversity of options, especially when it comes to selection of components and materials. For temperature-sensitive substrates, components, connectors and more, PulseForge soldering creates options where they are badly needed.

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Written by the PulseForge Applications Team

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