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Surface Mounting Guide

MLC Chip Capacitors

PCB BOARD DESIGN

To avoid many of the handling problems, AVX recommends that MLCs be located at least .2" away from nearest edge of

board. However when this is not possible, AVX recommends that the panel be routed along the cut line, adjacent to where the

MLC is located.

Solder Tip

Solder Tip

Preferred Method - No Direct Part Contact

Poor Method - Direct Contact with Part

No Stress Relief for MLCs

Routed Cut Line Relieves Stress on MLC

COMMON CAUSES OF

MECHANICAL CRACKING

The most common source for mechanical stress is board

depanelization equipment, such as manual breakapart, v-

cutters and shear presses. Improperly aligned or dull cutters

may cause torqueing of the PCB resulting in flex stresses

being transmitted to components near the board edge.

Another common source of flexural stress is contact during

parametric testing when test points are probed. If the PCB

is allowed to flex during the test cycle, nearby ceramic

capacitors may be broken.

A third common source is board to board connections at

vertical connectors where cables or other PCBs are con-

nected to the PCB. If the board is not supported during the

plug/unplug cycle, it may flex and cause damage to nearby

components.

Special care should also be taken when handling large (>6"

on a side) PCBs since they more easily flex or warp than

smaller boards.

REWORKING OF MLCs

Thermal shock is common in MLCs that are manually

attached or reworked with a soldering iron. AVX strongly

recommends that any reworking of MLCs be done with hot

air reflow rather than soldering irons. It is practically impossi-

ble to cause any thermal shock in ceramic capacitors when

using hot air reflow.

However direct contact by the soldering iron tip often caus-

es thermal cracks that may fail at a later date. If rework by

soldering iron is absolutely necessary, it is recommended

that the wattage of the iron be less than 30 watts and the

tip temperature be <300ºC. Rework should be performed

by applying the solder iron tip to the pad and not directly

contacting any part of the ceramic capacitor.