PCB Mounting Guidelines

Optimizing X2Y Performance with Proper Attachment Techniques

Use of solder mask beneath component is NOT recommended because of flux/contaminant entrapment.

Optimizing X2Y Performance on the PCB

X2Y capacitors deliver excellent performance in EMI/RFI filtering and Power Bypass applications. Physical and electrical placement on the PCB is critical in achieving good results. A low inductance, dual ground connection is mandatory.

For EMI Filter applications, low inductance PCB routing examples are shown in figures 1 and 2. Figures 3-5 show unbalanced and high inductance connections and should be avoided. For more information  see X2Y EMI Filter Evaluation and PCB Design Guidelines.

EMI Filter Applications: stray inductance must be minimized between signals and the A and B capacitor pads.G1 and G2 connections should be low inductance connections as well. Use star or daisy chain routes, rather than "T" to capacitor pads as show in Figure 1. Read: NEW - X2Y EMI Filter Evaluation & Design Guide for comprehensive information.

Figure 1	Figure 2	Figure 3
Figure 4	Figure 5

PDN Bypass applications

For PDN / Bypass applications the figures on the right compare the X2Y recommended layout against a poor layout. Because of its long extents from device terminals to vias, and the wide via separation, the poor layout exhibits approximately 200% L1 inductance, and 150% L2 inductance compared to recommended X2Y layouts. For more information see X2Y Power Bypass Mounting.

Lab Soldering Precautions

Ceramic capacitors (X2Y® and standard MLC types) can be easily damaged when hand soldered. Thermal cracking of the ceramic body is often invisible even under a microscope.  Factors that increase thermal cracking risk:

1. 4 terminals to solder can increase hand-soldering time and temperature exposure
2. Pb-free solders have higher reflow temperatures
3. Low inductance connections to ground are inherently good heat-sinks

A damaged component may exhibit a short circuit immediately and not recover, or may operate with intermittent Insulation Resistance (IR) levels. If you are not achieving expected results and have followed the other guidelines carefully, check to see you are adhering to the soldering guidelines below:

• Always pre-heat the PCB and component to within 50°C of solder reflow temperature at 2°C/sec. maximum.
• Use contact-less hand solder tools such as a hot air pencil, IR lamp, etc.
• Avoid over-heating of the ceramic component, temperature limit: 260°C for 20-30 seconds max.
• Use a soldering iron as last resort; 20W max. tip, NO CONTACT with ceramic, limit solder time to 5 seconds max.

A reliable, cost effective prototype PCB reflow soldering process is possible using a household toaster oven. There are several good procedures available on-line by googling "Toaster Oven Soldering"

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