Current Issue The International Reference for Chip-Scale Electronics, Flip-Chip Technology, Optoelectronic Interconnection and Wafer-Level Packaging January - February 2002 Email the editor

Infomation on products or services covered in this article

By Ron Iscoff, Editor

Photo shows the dispensing operation at STATS' Singapore facility.

Following the nearly year-long slide in capital equipment sales, makers of fluid dispensing systems are re-examining what performance levels users will demand in next-generation equipment.

The answers are familiar ones: improved positional accuracy, higher throughput, lower maintenance and lower cost of ownership. This last item is likely to come under increased scrutiny from users who, like the machine suppliers, have been buffeted by evaporating capacity demands.

A "typical" gantry-style, highly automated dispense system doesn't cost a great deal more than a high-end automated wire bonder, averaging $100K, without options. (They can run up to $400K, however, with an impressive range of bells and whistles added.).

However, the burdens placed on the dispensing tool-in terms of flexibility and application-are likely to be more demanding. Can it handle conductive epoxies, dam and fill, optical-grade materials, solder paste, underfills, etc.? And the list goes on.

It's vital for the handful of dispensing tool makers to hit the nail on the head, when it comes to product refinement. It's also likely that several next-generation tools will target opto/photonics final device and module assembly and packaging tasks, too.

Figure 1. The Asymtek Millennium M-2020 features patented mass flow calibration, vacuum-needle purge station and needle heater and sensor.

Fewer New Product Introductions

In 1999-2000, the industry witnessed a flurry of new dispensing machines. Cash-strapped dispensing tool makers are unlikely to repeat that grand scale of product introductions this year, instead focusing their sights more on enhancements to existing platforms. Likely changes will focus on the near-micro-at the needle or pump level-rather than on the macro of building a bigger/smaller cabinet.

Users such as Silicon Precision Industries Ltd. (SPIL) would like to see "machines with needles that clog far less often than today's versions." This might be accomplished, according to SPIL's J.Y. Hsu of the company's R&D Section in Taiwan, by reducing the length of the blunt-tipped steel needle or using the newer machined needles.

Additionally, says Hsu, simplified valve (and needle) cleaning-possibly with ultrasonic methods-would be useful.

Finally, according to Hsu, improved dispensing accuracy and control by increasing the z-axis precision, would be desirable.

SPIL competitor STATS, Singapore (lead photo), says key challenges include the type of piston, valve or screw mechanism that impacts consistency and accuracy.

While available dispensing tools offer some flexibility for writing dispense patterns, this is often limited in the number of segments and variations in length and thickness per segment, observes Dr. B.J. Han, STATS chief technology officer.

Dr. Han would also like to see:

• Unlimited dispense pattern size from smallest dot to segments >1 inch

• Auto-correction for the change in material viscosity over time

• Auto-dispense height correction and detection of surface warpage condition

• Accurate epoxy volume sensor, which prevents rejection of parts with insufficient epoxy. (He notes that these sensors are on the market, "but they have not yet proven their accuracy.)

Figure 2. Inside the M-2020, the system's dual-action dispensing head and two-lane changer increase dam and fill throughput.	Figure 3. DIAS Automation's AD-33 is a fully automatic programmable dispensing tool equipped with magazine-to-magazine handling.

Supplier Viewpoints

Key features that support faster return-on-investment will include pumps that are easy to clean and program, enabling users to switch over to different applications quickly, according to Alec Babiarz, Asymtek senior vice president.

Key features that support return-on-investment will include pumps that are easy to clean, systems that are easy to program and that allow users to quickly switch applications.

Gary Helmers, vice president of Creative Automation's Dispensing Division, Sun Valley, Calif., observes that the next generation of fluid dispensing equipment will incorporate digital dispensing technology.

This, says Helmers, will include the ability to create fluid structures (dots, beads, dams, encapsulation) pixel by pixel. Digital technology will mean much greater control of volume, shape and placement, which will result in superior flexibility, repeatability and throughput.

"Fluid pixels down to 0.005 inch in diameter (less than one nanoliter), will be required to properly deliver very small volumes of conductive epoxy, optoelectronic adhesives, underfills and other materials."

Figure 4. GPD Global's MicroMax Series offers a work area of 305 x 305 mm and features two valves, camera and surface sensor.	Figure 5. The Vortexx system, manufactured by Speedline Technologies' CAMALOT Division, is dedicated to production of Tessera's µBGA package.

Smaller Substrates

At dispensing tool supplier GPD-Global, Grand Junction, Colo., Christian Vega, business development manager for liquid dispensing, emphasizes that substrates are becoming "smaller and smaller, which puts more stringent requirements" on manufacturing equipment.

Vega says that placing smaller and denser components on smaller substrates will require "highly sophisticated 'smarter' vision systems that will enable operators to view multiple-level substrates with features that measure no more than 0.005 inches. These vision systems will likely need a lighting system that will adapt to the substrate's surface."

Additionally, the ability to dispense micro volumes (diameters under 0.008 inches) of material accurately and repeatedly will be needed for the upcoming miniature components.

The placement of micro-volumes of material, adds Vega, will also require a precision positioning platform allowing for placement within ±0.0015 inches.

Figure 6. CAMALOT's Xyflex is targeted at high-volume production uses in dam and fill, encapsulation and underfill.

'Pushing the Dispense Envelope'

Stephen Shepard of Speedline Technologies Inc., Franklin, Mass., says that the miniaturization of components for optical networks, telecom, defense and medical electronics will require precision positional accuracy with exceptional pump control.

Shepard, SMT dispensing product manager, says that CAMALOT's Xyflex Pro platform will meet the more-demanding needs for dispensing solder paste and conductive epoxy for these applications.

"Components such as precision linear servo motors with linear encoders enable the XyflexPro to accurately locate the dispense unit over the substrate surface," Shepard adds.

Using Windows NT as the user interface allows flexible programming of dispense parameters, including auger rotation, RPM and programming resolution to fractional degrees of rotation.

Conclusion

Don't look for great deal more horsepower in dispensing equipment that already delivers good repeatability, high throughput and placement accuracy-nor for a lot more automation.

For the next generation, however, expect dispensing tools to deliver reduced cost of ownership and increased incremental enhancements with major software tweaks, more reliable pumps and better dispensing nozzle mechanisms.