Product News

Phone (315) 426-8110 or email donh@hybridcircuit.com

Solving PC Design Problems with Direct Bonding and Thick Films

By Terry J. Barber, Dynamic Hybrids, Inc., Syracuse, NY

Direct Bond Copper (DBC) has traditionally been the province of a few large companies. This process involves bonding highly conductive copper foils directly to substrates, and is especially useful for manufacturing hybrid circuits and packages with high power-handling capability. Substrates used are most commonly ceramic, alumina, and beryllia, which all have excellent high-temperature characteristics.

Suppliers who have a limited scope, catering to a specific service or single venture, cannot be competitive in today's market. Buyers are cautious, and companies in general are seeking to keep their manufacturing costs as low as possible. Many of them are looking to outsourcing as a viable option. Whether outsourcing or procuring product, it is important to partner with a subcontractor that can supply a wide range of products and capabilities as well as being responsive to the buyer's requirements, coupled with the experience and technology that is needed.

Controlling the manufacturing environment from start to finish becomes possible with this marriage of direct bond copper hybrid circuits and thick film hybrid circuits all under one roof.

While the DBC market has so long been handled by larger firms, thick film printing has been produced by smaller independent companies. One company, Dynamic Hybrids, Inc. (DHI), has broken this status quo by combining the benefits of DBC for a conductor base or heat sink, and the ability to screen print thick film pastes to form passive, conductive, resistive, or insulating circuit elements. With the ability to control environment, thick film copper can be incorporated along with these elements. This only heightens surface mount possibilities.

Thick film, including copper, engineering capabilities, and now DBC, top off this well rounded company that has the idea in mind that, “dynamite comes in small packages.” One benefit of hybrid circuits made from the rigid substrates of ceramic and alumina is that they can operate under more power and withstand a much higher temperature. Power dissipation of any device is limited by the medium to which it is mounted. This is critical for surface mount and chip devices. When the mounting medium is fiberglass (FR4), the boards have poor thermal conductivity. This causes higher component temperatures, and therefore increased reliability issues. DBC can take the power load with the ceramic/alumina as the insulating element. By utilizing thick film and/or DBC technology on ceramic it becomes possible to increase the circuit's ability to dissipate power dramatically. This type of substrate and circuit creation becomes especially attractive if a circuit design has suffered from heat-related component failure. It also provides a ready solution in situations where SMT board designs have been limited because of thermal considerations.

Multilayers on Ceramic

Multilayer copper traces thicker than 3 oz. are also difficult to achieve with a fiberglass board. DHI utilizes a minimum of three or more layers of dielectric between conductive layers, depending on application requirements. With today's substrates, DBC hybrid circuits can be printed that have as many as 10 conductor layers. Screen-printed resistors can be multilayered and laser trimmed from 10 ohms to 10 Megohms with less than 0.1 percent tolerances, and higher values can be achieved using special processes. Capacitors can also be multilayered and laser trimmed.

DBC can be double-sided and use feedthroughs for interconnection. Holes in the ceramic can either be utilized to attach power-generating components for the current-carrying ability or ground connections directly to the DBC. The holes can also be used for attaching to a heat sink. Wraparounds to meet the board designer's requirements are also available. This is especially helpful when there are real estate issues or shielding problems due to adjacent high-frequency interference.

In another area, meeting the special needs of operating in harsh environments can also be handled by DBC. In fact direct bonding is an especially appropriate technology to use in the manufacture of a hermetic package designed to operate in harsh environments. Off-hanging leads for input/output and pin connectors to the next higher assembly can be integrated in the design with no additional lead frames needed.

Combining these technologies is not only convenient for the customer, it also cuts costs and minimizes the conflicts of different processes used between companies.

There are three classes of DBC available, which can be etched in a heat-spreading pattern. Electroless plating atop the DBC is always an option that provides a solution to potential problems with oxidization when wire bonding and soldering. The sizes are as diversified as the applications, with the largest thick film printing size being 6 x 6-in., and the largest DBC size 3 x 5-in., and up to 12 mils thick. Combining these technologies is not only convenient for the customer, it also cuts costs and minimizes the conflicts of different processes used between companies. Shipping no longer involves a complex process of fragile pieces shuttling between companies — a procedure that can be both time-consuming and expensive. The process also can fit readily into each company's schedule, meeting difficult-to-impossible deadlines.

Dynamic Hybrids, Inc., founded in 1992, provides engineering and management people with many years of experience in the hybrid circuit industry. The company is well known as a high-quality, low-cost source for hybrid circuits. While it has primarily been a thick-film gold, silver, and copper manufacturer, DHI now offers direct bond copper technology, wirebonding, seam/seal welding, and solder assembly reflow — and this can all be in combination for a truly problem-solving hybrid product. Approximately 60 percent of the company's output is directed to the military sector, a fact that attests to the products' inherent reliability. Products range from high reliability microwave/radar applications to high volume commercial products. In addition, DHI offers design support options utilizing internal CAD design techniques, and the company is MIL-I-45208 compliant.

Using the available design and engineering expertise, upgrades can be implemented more easily when the design and production development issues are already to the engineers. This experience comes through for modifications of preexisting designs.

Facilities include state-of-the-art test equipment such as x-ray inspection to assure QC for Medical, Fiberoptic, Microwave, Military and Surface Mount Device assemblies. The company can create specialty designs and meet military applications, all including assembly as well as providing a variety of wirebonding and packaging capabilities to meet virtually any problem-solving hybrid need.

For more information, contact:

Dynamic Hybrids, Inc.,
1201 E. Fayette St.,
Syracuse, NY 13210.
Tel: 315-426-8110; Fax: 315-475-8460.
Web: http://www.hybridcircuit.com