5.4: Surface-Mount Components

The majority of the RF and microwave design effort goes into developing modules and interconnecting modules on circuit boards. With these the most common type of component to use is surface-mount. Figure 5.3.3(a) shows a two-terminal element, such as a resistor or capacitor, in the form of a surface-mount component. Figure 5.3.3(b and c) show the use of surface-mount components on a microwave circuit board.

Designation	Size (inch x inch)	Metric Designation	Size (mm x mm)
$01005$	$0.016 \times 0.0079$	$0402$	$0.4\times 0.2$
$0201$	$0.024 \times 0.012$	$0603$	$0.6\times 0.3$
$0402$	$0.039 \times 0.020$	$1005$	$1.0\times 0.5$
$0603$	$0.063 \times 0.031$	$1608$	$1.6\times 0.8$
$0805$	$0.079 \times 0.049$	$2012$	$2.0\times 1.25$
$1008$	$0.098 \times 0.079$	$2520$	$2.5\times 2.0$
$1206$	$0.13 \times 0.063$	$3216$	$3.2\times 1.6$
$1210$	$0.13 \times 0.098$	$3225$	$3.2\times 2.5$
$1806$	$0.18 \times 0.063$	$4516$	$4.5\times 1.6$
$1812$	$0.18 \times 0.13$	$4532$	$4.5\times 3.2$
$2010$	$0.20 \times 0.098$	$5025$	$5.0\times 2.5$
$2512$	$0.25 \times 0.13$	$6432$	$6.4\times 3.2$
$2920$	$0.29 \times 0.20$	$-$	$7.4\times 5.1$

Table $\PageIndex{1}$: Sizes and designation of two-terminal surface mount components. Note the designation of a surface-mount component refers (approximately) to its dimensions in hundredths of an inch.

$L_{\text{nom}}$ $(\text{nH})$	$900\text{ MHz}$		$1.7\text{ GHz}$		SRF $(\text{GHz})$	$R_{\text{DC}}$ $(\Omega)$	$I_{\text{max}}$ $(\text{mA})$
	$L\:(\text{nH})$	Q	$L\:(\text{nH})$	Q
$1.0$	$0.98$	$39$	$0.99$	$58$	$16.0$	$0.045$	$1600$
$2.0$	$1.98$	$46$	$1.98$	$70$	$12.0$	$0.034$	$1900$
$5.1$	$5.12$	$68$	$5.18$	$93$	$5.50$	$0.050$	$1400$
$10$	$10.0$	$67$	$10.4$	$85$	$3.95$	$0.092$	$1100$
$20$	$20.2$	$67$	$21.6$	$80$	$2.90$	$0.175$	$760$
$56$	$59.4$	$54$	$75.4$	$48$	$1.75$	$0.700$	$420$

Table $\PageIndex{2}$: Parameters of the inductors in Figure 5.5.1(a). $L_{\text{nom}}$ is the nominal inductance, SRF is the self-resonance frequency, $R_{\text{DC}}$ is the inductor’s series resistance, and $I_{\text{max}}$ is the maximum RMS current supported.

A two-terminal surface-mount resistor or capacitor is commonly called a chip resistor or chip capacitor. These can be very small, and the smaller the component often the higher the operating frequency due to reduced parasitic capacitance or inductance. Common sizes of two-terminal chip components are listed in Table $\PageIndex{1}$. With a chip resistor or chip capacitor, the parasitic inductance determines the maximum operating frequency with the self-resonant frequency, in the case of a chip capacitor, being when the capacitance resonates with the parasitic inductance. The usable maximum frequency is below the self-resonant frequency.

Figure 5.5.1(a) shows an inductor in a surface-mount package and details are shown in Figure 5-7(b). This inductor is wound on a dielectric former, which, unfortunately, increases the inductor’s parasitic capacitance. The resonance of this capacitance with the inductance establishes the self-resonant frequency (SRF) of the inductor. The inductor is useable as an inductor at a frequency backed-off from the SRF. The parasitic capacitance is reduced if the inductor has an air core, as for the inductors shown in Figure 5.5.1(c), with details shown in Figure 5.5.1(d). The air enables the inductor performance to be improved if the size remains the same or the inductor is smaller for comparable performance. The performance of the two types of inductors is listed in Tables $\PageIndex{2}$ and 5.5.1.