BOARD DESIGN CONSIDERATIONS
The amount of solder applied to the chip capacitor will influence the reliability of the
device. Excessive solder can create thermal and tensile stresses on the component
which could lead to fracturing of the chip or the solder joint itself. Insufficient or
uneven solder application can result in weak bonds, rotation of the device off line or lift-
ing of one terminal off the pad (tombstoning).
The volume of solder is process and board pad size dependent. WAVE SOLDERING exposes the
devices to a large solder volume, hence the pad size area must be restricted to accept an amount of solder which is not detrimental to
the chip size utilized. Typically the pad width is 66% of the component width, and the length is .030” (.760 mm) longer than the termi-
nation band on the chip. An 0805 chip which is .050” wide and has a .020” termination band therefore requires a pad .033” wide by
.050” in length. Opposing pads should be identical in size to preclude uneven solder fillets and mismatched surface tension forces which
can misalign the device. It is preferred that the pad layout results in alignment of the long axis of the chips at right angles to the solder
wave, to promote even wetting of all terminals. Orientation of components in line with the board travel direction may require dual
waves with solder turbulence to preclude cold solder joints on the trailing terminals of the devices, as these are blocked from full expo-
sure to the solder by the body of the capacitor.
Restrictions in chip alignment do not apply to SOLDER REFLOW or VAPOR PHASE processes, where the solder volume is con-
trolled by the solder paste deposition on the circuit pads. Pads are designed to match or slightly exceed the width of the capac-
itor, with length .030” (.760 mm) greater than the chip terminal band width, to provide a wetting area for a full solder fillet.
7
RECOMMENDATIONS
Preheat/Cooling rates not to exceed 120°C/minute.
DT spikes to max temperature not to exceed 100°C
250
225
200
175
150
125
100
75
50
20
40
60
80
100
120 140
160
180
200
SECONDS
SOLDER ATTACHMENT RECOMMENDED PROFILES
SOLDER WAVE
VAPOR PHASE
SOLDER REFLOW
NOVACAP
publishes
a
Technical Brochure which pro-
vides detailed information on the
properties
of
ceramic
chip
capacitors, dielectric behavior,
product classifications, test and
quality standards, and other
information relevant to their
use. The NOVACAP Technical
Brochure is available upon
request. For quick reference
see the Brochure on the
NOVACAP Website at
www.novacap.com.
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
