Authored By:
Ralph Birnbaum, Ph.D., Stéphane Etienne, Michael Zenou,
ioTech
Israel
Summary
Solder paste balls are being deposited at tighter and tighter resolutions. Various solutions have been proposed, but there is always a trade off somewhere. The tighter resolution can come at expense of custom materials, such as in inkjet, or speed, such as in dispensing. Ideally, we would have a solder ball dispensing solution that had the throughput of the traditional analog solutions, such as screen printing, with the accuracy and flexibility of traditional digital solutions, such as jetting and needle dispensing.
With Continuous Laser Assisted Deposition (C.L.A.D.) there is no longer any trade off between materials and other parameters. This contact-less technology has no nozzle and no mesh. It can deposit drops from materials above 300,000 cPs (300Pa.s) at high speed and high resolution. The high viscosity window allows standard certified solder pastes to be used from Type 4 and above, without any reformulation.
This laser assisted deposition technology can be applied to several applications, but in this paper we will focus on solder paste deposition. In addition to standard solder paste materials, most other materials can be printed too, up to very high viscosities. This includes conductive materials, polymers, ceramics and silicone. The C.L.A.D. solution allows up to 5 different materials to be printed.
In the C.L.A.D. technology, a material, evenly coated on a transparent carrier film, passes under a laser. The laser applies a short burst of energy to it. This releases perfectly consistent drops of material onto the substrate below. The material drops can then be sintered or cured inline, in the same machine. Minimum resolutions are higher than currently achievable resolutions. Multiple component sizes can be handled, as well as component heights. Very high thickness to diameter rations can be achieved, sometimes by multiple passes.
With these multiple benefits, the technology has been widely recognized by industry as well as investors.
Conclusions
There are many benefits of using the CLAD technology for depositing one material upon another. This paper has focused on printing solder paste balls on a substrate, for which there are several benefits:- Standard certified solder paste of Types 4 through Type 8 can be used. No reformulation of the solder paste required.
- Throughputs are comparable to screen printing (up to 7M dots/hour), but with the accuracy and flexibility of digital technologies.
- Resolutions are finer than with traditional techniques, e.g. solder balls of 100μm with a standard Type 6 solder paste.
- Contactless means there are no masks to prepare, clean and store, nor nozzles that get clogged.
- Supports complex designs with landing pads of varying shapes and sizes.
- Very high diameter to height aspect ratios.
- High repeatability: Uniform layer height
- Multiple materials: in addition to solder paste, epoxy dots can be printed as well SMA’s
The CLAD technology enables new designs to break through old design limitations, with higher density of solder balls, and greater aspect ratios. This is all done without sacrificing throughput, and without requiring any special solder pastes.
Overhead and maintenance is kept to a minimum by removing the need to prepare masks, or to clean clogged nozzles. The high throughput enables the potential to replace several machines in some cases, saving on floor space, labour and handling costs.
Initially Published in the SMTA Proceedings
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