Assembly innovations: sweet dreams are made of these: a review of amazing new products and technologies.

The two premier trade shows in the electronics assembly industry are Productronica, held every other year in Munich, and APEX, held annually in California. Each is a showcase of new equipment and materials. If a manufacturer is going to present its latest and greatest product offerings, these shows provide the best opportunity to do so. Unfortunately, due to the September 2001 terrorist attacks and the faltering economy, attendance was down at both Productronica, held in November 2001, and at APEX, held in January 2002. Some readers may not have had the chance to attend and, if so, missed some of the new industry advances unveiled at the show. With the help from two associates, I have selected the top products/technology to share here.

One misconception at industry shows is that the newest, greatest innovations will be found in the largest, most elaborate exhibit booths, which is not necessarily true. Sure, the large booths may feature announcements of acquisitions, mergers and alliances, automated optical inspection (AOI) systems and faster pick-and-place machines to peruse. However, some of the most fantastic advances can be virtually hidden away. The casual observer may have missed these great advances, but I found them!

Advances in Solder Paste

Two exciting advances in solder paste were featured. One lesser known, but certainly innovative, Icelandic manufacturer has derived a no-clean flux whose potential residue decomposes into carbon dioxide after reflow. Hence, no residue in the oven or on the printed circuit board assembly (PCBA).

Equally exciting was the lead-free offering from a Yugoslavian solder manufacturer that features an alloy with aluminum. The eutectic alloy has a melting point of around 190[degrees]C with a full liquidus temperature of around 205[degrees]C. The company reportedly discovered this alloy when a building adjacent to their laboratories, which happened to have aluminum siding, was bombed into oblivion during NATO air strikes. The company experimented with the resulting fused metals and discovered this important alloy.

Printing Technologies

Printing technology has taken a radical move forward with a new approach to stencil, thanks to a firm in Nebraska. Using plasma technology, apertures are formed by electronic pulses, much like a display, but three-dimensional. As a result, the stencil is programmable. Imagine--one stencil fixed in place on the printer. Aperture location is derived from Gerber files, much like a conventional etched laser or electroformed stencil, but electrically formed (and closed) from one job to another. No stencil changeover and, between job cleaning, no costly inventory of stencils. A stencil can be created in seconds, not hours, in situ on the printer.

The plasma-manipulated stencil (PMS), as its creators have named it, also has the advantage of being dynamic. Again, using electrical pulses, the stencil can be programmed to virtually squeeze the solder paste through apertures. The manufacturer believes this technology could lead to the obsolescence of the squeegee, as well as assure clean, un-blocked apertures--eliminating the need for stencil cleaning.

Pick-and-Place Technology

A firm in New Zealand has introduced a pick-and-place system that appears to "do it all." Using four vertical rotary heads, mounted on four separate gantries operating asynchronously, the system can place 0201s to 31.75 x 31.75 mm components [quad flat packs (QFPs), ball grid arrays (BGAs), odd-form components, connectors, etc.] with +/- 1-micron placement accuracy. The system also features placement rates of up to 40,000 parts per hour--regardless of the size of the part. In addition to on-the-fly part verification, bar-coding, smart-feeders and laser-based lead-coplanarity checking, the system also incorporates an onboard AOI system that verifies integrated circuit (IC) pin 1 orientation prior to placement. The system can check area-array packages, including high pin count flip-chip, for missing or malformed bumps--all without impacting placement speed.

In addition, the system can utilize almost any other manufacturer's feeders. Tape feeders from 8 mm to 72 mm, whether electrical or mechanical, can be accommodated via adapter fixtures. Existing inventory (and investment) of feeders will not be obsolete with this machine. Most manufacturers' roll-up feeder carts can also be adapted.

Merging automation with component technology, a prominent manufacturer in Wales introduced a system that places a generic value resistor and trims it to the proper resistance--on the fly. Operating at a placement rate of approximately 10,000 per hour (a rate expected to drastically increase in the very near future), a resistor is picked up and, while in transit to its designated PCBA location, is trimmed to a programmed value by a laser mounted in the placement head. This advancement greatly reduces the number of resistor feeder locations, since one resistor can be adjusted to a wide variety of resistance.

Reflow and Wave Soldering Advances

Soldering technology is making great strides as well. At long last (as I predicted many years ago), microwave technology has been applied to reflow soldering thanks to an Australian company. Using a fixed-frequency microwave source and a proprietary oven atmosphere, the methodology is fast, efficient and economical. With Microwave Reflow Soldering, only the interconnects and solder paste are heated for approximately four to six seconds. Because the applied energy is rather intense and no oxidation is taking place in the process, many applications will not even require flux. No incidental heating of, or damage to, components or the printed circuit board (PCB) substrate occurs--even with higher temperature lead-free alloys. Since the PCB material never ascends above the glass transition temperature, warpage is a thing of the past.

Just as selective soldering was an evolution and improvement over wave soldering, selective soldering itself is evolving. During Productronica, a small firm from Lichtenstein demonstrated a prototype of a system that uses programmable induction soldering for accommodating through-hole interconnections on mixed-technology PCBAs.

Conclusion

I want to thank my associates, Jim Hall and Ron Daniels, for helping locate the best products and technologies featured at recent shows. Each of us wishes the readers of Circuits Assembly a very happy April Fools' Day. Remember, we're all in this together.

Phil Zarrow is president and surface-mount process consultant for ITM Consulting, Durham, NH; [phone]; www.ITM-SMT.com