This month issue An Independent Journal Dedicated to the Advancement of Chip - Scale Electronics September - October 2000 Email the editor

By Ron Iscoff, Editor

Few segments of the semiconductor equipment market are watching the no-lead solder debate with more interest than the makers of reflow ovens. To this equipment manufacturing segment, the adoption of no-lead solders vs. conventional tin/lead-based alloys carries a host of practical, bottom-line-driven implications.

Figure 1. The ACCEL MicroPro offers a total system footprint its manufacturer describes as "a fraction of the traditional line footprint."

Additonally, since no-lead solder replacements demand higher reflow temperatures than lead-based solders, oven suppliers are faced with some very real concerns about time/temperature and, most significantly, process control. Finally, as reflow oven makers, themselves, are quick to point out, tools designed for SMT applications one or two decades ago have lost their utility for the CSP market.

Suppliers Bullish

However, even with lead-free solder questions hanging over the industry, oven suppliers are nothing if not bullish about business conditions over the next year or so.

"The market for solder reflow systems will continue to boom over the next year," predicts Eddy Nijhof, product line manager for Vitronics Soltec, Stratham, N.H.

The market, adds Nijhof, is being driven by such things as Internet and wireless technology, including cell phones and the Blue-tooth initiative.

David Muhs, president of Scientific Sealing Technology, Downey, Calif., is likewise bullish on prospects for next year. "The market will continue to grow," he says, "and users will look for systems that provide the lowest total cost of ownership while producing results with the highest possible quality."

Figure 2. The Quad Systems QRS Plus convection reflow oven can monitor and report specific temperatures at every PWB site during processing.

'Growth Phase'

Rich Feely, marketing manager for reflow oven maker Research International, Eden Prairie, Minn., concurs that reflow ovens are in a growth phase. "The market for solder reflow systems has grown steadily over the past few years. "Even when the semiconductor front-end business was in a slump," Feely adds, "back-end conversion to CSPs remained steady."

In addition, he says, "The days of using standard SMT ovens for specialized semi-conductor manufacturing are ending."

Vitronics Soltec's Nijhof agrees. It's time, he says, to bring reflow soldering gear out of the shadow of screen printers and pick-and-place equipment, and "to make people aware that while one may spend considerable money on this higher-cost equipment, without a good reflow system, high yields may not be achieved."

"In the past, reflow oven suppliers only offered their standard, SMT focused equipment to the packaging industry," observes Paul Knox, vice president/general manager for Speedline ACCEL, Plano, Texas.

Figure 3. The WB Series is a conduction system that employs RTC's TriBelt conveyor transport.

Form Factors

Knox says that as the advanced packaging market "gains significant momentum, there will be a small group of suppliers who will recognize that advanced package form factors-and therefore tool requirements-are very different from those used in SMT."

This recognition, contends Knox, "will lead to a revolution in the way equipment suppliers approach development programs."

For example, this year BTU International, North Billerica, Mass., introduced its new Pyramax reflow system. "In creating Pyramax, we re-examined every element of our products, from the technology to the construction, operation and maintenance," says Bob Bouchard, Pyramax product manager.

Figure 4. Scientific Sealing Technology's HV-2200 GT system is said to be ideal for MEMS assembly.

No-Lead Solders

With more questions than answers now circulating, suppliers of reflow systems are spending considerable thought (and resources) on meeting process specs for no-lead solders.

The reflow market will undergo "a single, significant change over the next year," as it deals with no-lead alternates, according to Jeff Stong, product marketing manager for Quad Systems Corp., Willow Grove, Pa.

While testing for no-lead alternatives is still underway, no-lead compounds "will affect the type of oven that is needed and the system options required," adds Stong. These may include such components as additional cooling zones, the number of heating zones, PWB temperature monitoring systems, flux containment, etc., he notes.

"Due to the higher temperatures required with no-lead pastes, the demand for such items as temperature monitoring and reporting systems (SPC) on ovens will become important," Stong adds.

"One (temperature) profile fits all is a thing of the past if highest quality soldering is to be obtained," observes Marc Aldecoa, sales coordinator for Sikama International, Santa Barbara, Calif. The emphasis in the future, he says, will be on process control, "with each product having its own profile.

Figure 5. Sikama's Ultra Profile 2000 employs a combination of conduction and convection heating.

Single Steps

Reflow equipment technologies will continue to compete and process engineers will search for ways to collapse multiple reflow steps into single, simultaneous steps, according to Selina De Rose, applications engineer for Radiant Technology Corp., Fullerton, Calif. Moreover, she adds, "Tooling and selective heat-flow patterns will become more sophisticated."

Dr. Skip Fehr, executive vice president and CTO for IC assembler IPAC, San Jose, says users like IPAC are looking for reflow ovens that offer such items as:

• Excellent temperature profile control

• Temperature profile repeatability

• Heat transmission through conduction

• Smooth mechanical handling of wafers and parts

• Belt-speed control (low speed and wide range)

With more than two dozen makers of reflow ovens doing business, the market is highly competitive, with each supplier trying to "one-up" the competition. Here are a few of the industry's offerings with features described by their manufacturers as unique:

• ACCEL MicroPro (Figure 1) integrates reflow, cleaning and handling in one system. The handling takes advantage of the rectangular form factor of BGAs/ CSPs, and processes CSPs at a 90 degree orientation, along their shorter width, which allows for maximum product density inside the oven and cleaner for maximum unit throughput.

• Quad Systems QRST Plus Series (Figure 2) The Quad QRST Plus reflow ovens are capable of monitoring and reporting specific temperature for every PWB process or at every PWB site throughout the oven.

• Radiant Technology Corp. (Figure 3) Radiant's WB series is a conduction system that employs RTC's unique TriBelt conveyeor transport.

• Research International The ChipFlo is the only reflow oven, says Research International, customized for high-volume BGA productions. The unit's exclusive low velocity nitrogen convection (LVNC) transfers heat without blowing molten solder off the substrate.

• Scientific Sealing Technology (Figure 4) All of Scientific Sealing's machines offer solder reflow in both a vacuum and pressurized inert atmosphere. This environment produces void-free reflow without the use of flux. Since these systems use power and gas utilizes during only a small part of the duty cycle, operating costs are kept low.

• Sikama International (Figure 5) Sikama's patented line of reflow and curing ovens combines bottom-up conduction/convection and top-down convection technology with precision temperature calibration and purity of atmosphere for ultimate control of the reflow process.

• Vitronics Soltec (Figure 6) Units employ convection technology with a panel heater for an optimal mix between IR and convection heating.

Figure 6. The Victronics Soltec XPM 820N system employs convection technology with a panel heater for an optimal mix between IR and convection.

Users Benefit

While reflow oven makers attempt to forecast the future of low-lead/no-lead solders as a basis for their equipment design guidelines, reflow users-perhaps more than reflow equipment suppliers-stand to benefit the most from a continuing list of system improvements.

Next