Bonding Yields Better Parts

Bonding materials and heat sinks play a crucial role in the ongoing efforts to improve manufacturing efficiency. The tapes that keep chips in place during manufacturing are critical for keeping high-speed production lines running smoothly.

At the same time, these adhesive materials continue to do more to keep chips cool, an important factor as high-density semiconductors run at higher frequencies and generate more heat. Bonding materials can no longer serve just as attachment technologies — they must also help remove heat from microprocessors and other devices.

These materials often work in conjunction with heat sinks, which continue the task of transferring heat. As semiconductors continue to evolve, they will put more pressure on the adhesive materials that hold electronic products together.

Inherent tack assures precise placement

The Sil-Pad 1100ST Soft Tack family from the Bergquist Co. has inherent tack on both sides, with dual liners for easy placement needed for high-volume auto-dispensing applications. Thermal impedance for the fiberglass-reinforced and silicone-based material is 0.66C-in2/W at 50 psi.

The inherent tack eliminates the need for additional adhesive layers, simplifying assembly because the material can be repositioned on the target surface without quality problems.

Typical applications are the interface between automotive electronic control modules, power supplies, and motor controls. Standard sheet size is 12 × 12 inches, while rolls measure 12 inches x 250 ft. Both have a thickness of 0.012 inches. In 10,000 pieces, a 1 × 1 × 0.012 inch piece costs $0.115.

Aluminum heat sinks improve cooling by 40 Percent

Targeting BGAs and other hot components that don't get much air flow, Advanced Thermal Solutions is offering MaxiFlow heat sinks. The low profile heat sinks have a spread fin array that maximizes surface area for effective convection cooling. They are fabricated from lightweight extruded aluminum which minimizes thermal resistance from the base to the fins. With an air flow rate of just 100 linear feet per minute, device junction temperatures can be reduced by more than 40 percent below the temperatures achieved with other heat sinks.

MaxiFlow heat sinks are available in lengths and widths ranging from 10 x 10 mm to 60 x 60 mm, with heights starting at just 2 mm. Pricing begins at $2.50 in production quantities.

Conductive interface keeps hot chips cool

MH&W International is unveiling KoolBond, a thermally conductive interface that attaches heat sinks to hot PCB components. KoolBond consists of a fine woven, nickel-coated copper fiber matrix with a high-strength pressure sensitive adhesive. The woven copper closely conforms to irregular mounting surfaces on components and heat sinks, providing thermal impedance of 0.42°K sq inches/W in material thickness of 5 mils, and 0.74º K sq inches/W at 10 mil thickness.

Double-sided adhesive eliminates the need for screws, clips, or other hardware for mounting sinks to IC's, transistors, mosfets, op amps, and other components. A 10-mil thick KoolBond pad provides lap shear strength of 35.5 N/cm2. Its adhesive surfaces are protected by release liners for fast, peel and stick application.

The material comes in sheets and custom die-cut shapes, and it can be laser cut. Unit pricing for 5-mil thick KoolBond starts at $0.11 for 1 sq inch pieces in high-volume quantities.