Know what you are getting! By K. R. Philpot Director of Applications, Microsemi-Lowell more than solutions - enabling possibilities Microwave Diode Packages:

here is no subject that causes more problems and confusion for users of microwave diodes than the effects of the diode package. Packages always limit the performance of the circuit design, sometimes in unexpected ways. This paper will discuss the different types of packages available, the attributes of each, and the effects one might expect when used in some common circuit applications. Packages are a necessary evil. In a perfect world, all designs would make use of the unpackaged die, installed eutecticly and wire bonded into the circuit. But microwave diode packages afford protection for the...

Circuit implications of package parasitics Varactor diodes used in Voltage controlled oscillators (VCOs) demand the very lowest package parasitic inductance. This value will directly affect the maximum frequency which can be achieved. Package parasitic capacitance will limit the bandwidth and tuning linearity of the VCO. Because VCOs do not require power to be dissipated in the varactor, package thermal resistance is usually not important. As a general rule PIN diode switch applications demand the lowest possible parasitic capacitance. This value directly limits the isolation that can be achieved...

Microwave There are 3 package types which can be used at microwave frequencies above 6 gHz. Ceramic packages are the best performing microwave package styles available. They are hermetic and the type of choice for military and space applications. They are also the most expensive. They combine low parasitic inductance, low parasitic capacitance and can have superior thermal resistance characteristics as well. Most products are available in ceramic packages. Outline 30 and 79 are good examples (Figures 1 & 2) Style 30 MMSM™ packages combine the attributes of excellent microwave performance, surface...

Stripline packages for microwave are usually also ceramic and can be completely hermetic or have epoxy encapsulation. They combine low parasitic inductance, low parasitic capacitance and are designed specifically for stripline or microstrip construction. They can however have high thermal resistance and are not the best choice for applications which will result in high device dissipation. Style 17 (Figure 4) is hermetic, style 127A (Figure 5) is epoxy encapsulated Surface Mount There are 6 types that can be used for surface mount applications. Once again some fall into more than one category:...

Enhanced Performance Surface Mount (EPSM™) packages offer solid consistent performance for applications up to 6 gHz. Both parasitic inductance and parasitic capacitance are very low compared to conventional plastic injection molded surface mount packages. Thermal resistance is moderate but superior to plastic as well. Additionally there are a wide range of outlines from which to choose. And most products we offer are available in EPSM. Figures 7, 8, and 9 show some common EPSM outlines. Metal Electrode Leadless Faced (MELF) packages are specially designed for PIN diodes. They have low values...

Plastic SOT-23 packaged devices are rugged economical packages suitable for low power applications with frequencies up to 2 gHz. They have moderately high levels of all parasitics but are ideal for less critical higher volume commercial use Figure 11 shows the SOT-23 style package. Thru Hole Glass axial packaged diodes have been around for many years and are still popular today for UHF frequencies and below. Their hermiticity and proven environmental design are favorites for military requirements. They have very high thermal resistance which makes them unsuitable for high power applications....

Need help choosing? Our applications engineering department is always available to discuss your requirement and help you choose the optimum device and package to suit your technical and budgetary needs. Contact Ken Philpot direct at (978) 442-5616 or e mail: [email protected] more than solutions - enabling possibilities Microsemi Lowell 175 Technology Drive Lowell, MA 01851 USA Phone: (978) 442-5600 Fax: (978) 937-3748 www.microsemi.com All trademarks are of Microsemi Corporation