High Speed Soldering Using Laser Printing for the Assembly of Electronic Components

Recent advancements in printed circuit board (PCB) assembly and IC packaging technology demand high resolution for ultra-fine pitch components (<0.3mm and <60 m respectively), high throughput and compatibility with flexible substrates. These challenges are poorly met by the conventional deposition techniques (i.e. stencil printing), thus the need for a digital and high-resolution deposition technology is essential. In this context, Laser-Induced Forward Transfer (LIFT) can offer an excellent alternative: it is fully compatible with a wide variety of materials, it is environmentally friendly and offers versatile control over the printed volume with high throughput. In this work, a novel process for LIFT printing lead-free, jettable solder paste (powder size 15-25 m) is reported. A side-view imaging configuration is employed by coupling a LIFT setup with a high-speed camera for the real-time visualization of the ejection process. The experimental data from the captured videos are analyzed to determine morphological aspects. Transfers are achieved with diameters ranging from 50 to 150 m and printed volumes down to sub-nl. The fabrication of patterns, such as lines, on the PCB pads has been accomplished by scanning the laser beam over the donor surface (with 1 m/s scanning speed), creating consecutive jets which form overlapping droplets.