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A publication of the National Electronics Manufacturing Center of Excellence

January 2010

SMT Component Reliability for RF Applications

ISO 9001:2000 Certified

Michael D. Frederickson, EMPF Director

Barry Thaler, Ph.D. • bthaler@aciusa.org

EMPF Technical Director Empfasis Technical Editor

Paul Bratt • pbratt@aciusa.org Empfasis Editor

In this Issue SMT Component Reliability

for RF Applications ........................................1 Ask the EMPF Helpline!................................2 Mechanical Drop Shock Testing....................3

Tech Tips: Die Attach Dispensing Methods .......................................4

Manufacturer’s Corner: FocalSpot, Inc.........5 Reliability Concepts........................................6 Training Center Course Schedule ................12

ACI Technologies, Inc.

One International Plaza, Suite 600 Philadelphia, PA 19113 610.362.1200 • fax: 610.362.1290 Helpline: 610.362.1320 web: www.empf.org • www.aciusa.org

Industrial Advisory Board

Gerald R. Aschoff, The Boeing Company Jane Krueger, Rockwell Collins Richard Kidwell, ITT Industries, Avionics Division Gary Kirchner, Honeywell Dennis M. Kox, Raytheon Gregory X. Krieger, BAE Systems Edward A. Morris, Lockheed Martin Andrew Paradise, Northrop Grumman

T h e E M P F r e c e n t l y c h a r a c t e r i z e d t h e r e l i a b i l i t y o f s u r f a c e m o u n t R F c o m p o n e n t s . T h e R frequency band of interest was the X band (10.7 to 11.7GHz). A two pronged test for reliability of circuit card assemblies (CCA) was designed for both extreme thermal cycling and vibration. The rapid thermal cycling and extreme vibration testing simulates the total stress encountered by the assembly over the life of the product but accomplishes it in a relatively short period of time. In order to perform the reliability testing, a test vehicle consisting of a printed circuit board with test structures and components, was designed, fabricated, and assembled at the EMPF. F

Surface mount technology (SMT) components were selected that are both commonly used and have operating ranges up to the X band of the RF spectrum. A digital attenuator in a quad flat pack, no lead (QFN) package was used with supporting chip components in 0402 and 0603 sizes. Two surface mount hybrid couplers with different leads were installed, one with L leads and one with castellated leads. Side launch SMA connectors with through-hole ground connections were installed to allow connection to the spectrum analyzer.

The frequency range of the attenuator is up to 13GHz while the other RF components are less than 4GHz based on their application in the actual circuit.

CCA Design and Assembly

The test vehicle was designed to simulate a proposed board stackup and allow the mounting of the SMT RF components. Each board has six RF paths that pass through the components (Figure 1-1). To observe any effects of vibration and thermal cycling on the laminated board, three RF paths were designed with no components to act as controls.

Figure 1-1: Section of test vehicle with digital attenuator and couplers.

The component manufacturer’s data sheets were used to define the shapes and sizes of both the pads on the CCA and the cutouts for the solder paste stencil. The stencil thickness was 0.005" to allow the proper solder volume on the 0402 and 0603 chip component ends. The larger, castellated lead coupler required a stencil having a “window pane” feature to reduce the volume of solder used to solder the large center ground to the ground plane.

The solder paste selected is the type typically used for military assemblies (63/37 tin-lead solder with a no clean flux and a J-STD-004 classification of

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