In the beginning, when SMT assembly first began penetrating the board assembly market, it was thought that surface mount would work for office computer production, but never in critical areas such as military and medical applications. Today, it seems that these are two of the rock-steady areas to be in if you’re an EMS provider.
Much progress has occurred along the way to increase SMT assembly. In 1999, the FCC opened up bandwidth frequencies, spurring development of new markets for miniature low-power RF devices and specialized communication protocols for monitoring medical conditions and delivering medication to patients. Implanted medical devices, such as heart monitors, could communicate with external devices, uploading data to doctors for review without physically transporting patients to the hospital. In drug delivery, new electronics-controlled equipment allows patients to deliver their own medicine but with the added safety of dose and frequency control.
As assemblies shrink, board real estate becomes an issue. Especially with mixed-technology (through hole and SMT) boards, tight spacing makes soldering through-hole and SMT assemblies difficult for small medical devices. Selective soldering can resolve this challenge. This latest soldering development handled the density issue and met high heat requirements for soldering. For those connectors, capacitors, and digital displays still requiring through-hole plus SMT components, selective soldering fits.
Some mixed-technology PCB designs can still be wave soldered with carriers and masking, but stacked and double-sided assemblies are too intricate to be given this individualized approach to mass interconnection. Most assemblies using RF components are too complex to hand solder all of the through-hole devices without errors. Selective soldering equipment can be programmed to handle both in- and off-line programming. The equipment integrates easily with the rest of the automated production equipment.
The selective soldering process — with mini solder wave nozzles beneath the circuit boards, handling precise dip, drag, and small wave actions while flux is handled by spray, drop jet, or ultrasonics — is now a familiar sight. Through programming, the equipment can control the process and maintain line speeds.
Radio (RF) technology has grown at Merrimack-N.H.-based BAE Systems, where the firm recently completed its first real-time test of improved wireless communication technology. War fighters can now dispense critical communications without interruption during battle. The technology allows more traffic on networking systems. It gives users an advantage during air-to-air, air-to-ground, and soldier-to-soldier communications.
Under a $15.5 million Defense Advanced Research Projects Agency (DARPA) contract, BAE is developing wireless radios that can untangle interfering digital communications signals. The DARPA Interface Multiple Access (DIMA) program aims to increase network capacity and performance in highly congested mobile networks. The radios will allow multiple transmissions to occur simultaneously on one frequency and can support as many as five simultaneous conversations into the same time and frequency slot, even in the presence of severe near-far interference.
“With current technology, bandwidth is shared through assignment of unique time slots, frequency slots, or code words for each user, significantly limiting network performance,” said Brian Pierce, Ph.D., DARPA. “DIMA buys back the capacity loss caused by those limitations with technology that separates multiple, interfering digital signals.”
Known as multi-user detection, BAE Systems’ real-time technology enables users to communicate simultaneously on the same channel without centralized control or infrastructure. Recent experiments validated the technology in a mobile, ad-hoc network environment and demonstrated the vehicle-mounted DIMA radio’s ability to receive up to five simultaneous transmissions from different users while traveling at 15 mph.
“By next March, we expect to operate at speeds greater than 30 mph in highly interfering scenarios, and may even operate as high as 60 mph,” said Joshua Niedzwiecki, manager of BAE Systems’ communications and signal exploitation research group. “This would further validate the technology in more operational scenarios. If fielded in Iraq, for example, it could prove vital in areas where interfering electronic transmissions reduce the amount of transmittable military communications.”
With new applications and specialized equipment, both medical and military markets hold steady for EMS assembly inside the U.S. Both serve a growing need for RF communications in monitoring and communications.
Gail Flower, editor at large
Read Editorial Advisory Board member Craig Hunter's take on SMT in rugged applications: SMT Components Toughen Up for Rugged Applications