ICS8735-21 Datasheet, PDF (14/20 Pages) List of Unclassifed Manufacturers – 700MHZ, DIFFERENTIAL-TO-3.3V LVPECL ZERO DELAY CLOCK GENERATOR

ICS8735-21
700MHZ, DIFFERENTIAL-TO-3.3V LVPECL ZERO DELAY CLOCK GENERATOR
VFQFN EPAD Thermal Release Path
In order to maximize both the removal of heat from the package
and the electrical performance, a land pattern must be
incorporated on the Printed Circuit Board (PCB) within the footprint
of the package corresponding to the exposed metal pad or
exposed heat slug on the package, as shown in Figure 6. The
solderable area on the PCB, as defined by the solder mask, should
be at least the same size/shape as the exposed pad/slug area on
the package to maximize the thermal/electrical performance.
Sufficient clearance should be designed on the PCB between the
outer edges of the land pattern and the inner edges of pad pattern
for the leads to avoid any shorts.
While the land pattern on the PCB provides a means of heat
transfer and electrical grounding from the package to the board
through a solder joint, thermal vias are necessary to effectively
conduct from the surface of the PCB to the ground plane(s). The
land pattern must be connected to ground through these vias. The
vias act as “heat pipes”. The number of vias (i.e. “heat pipes”) are
application specific and dependent upon the package power
dissipation as well as electrical conductivity requirements. Thus,
thermal and electrical analysis and/or testing are recommended to
determine the minimum number needed. Maximum thermal and
electrical performance is achieved when an array of vias is
incorporated in the land pattern. It is recommended to use as many
vias connected to ground as possible. It is also recommended that
the via diameter should be 12 to 13mils (0.30 to 0.33mm) with 1oz
copper via barrel plating. This is desirable to avoid any solder
wicking inside the via during the soldering process which may
result in voids in solder between the exposed pad/slug and the
thermal land. Precautions should be taken to eliminate any solder
voids between the exposed heat slug and the land pattern. Note:
These recommendations are to be used as a guideline only. For
further information, please refer to the Application Note on the
Surface Mount Assembly of Amkor’s Thermally/Electrically
Enhance Leadfame Base Package, Amkor Technology.
PIN
SOLDER
EXPOSED HEAT SLUG
SOLDER
PIN
PIN PAD
GROUND PLANE
THERMAL VIA
LAND PATTERN
(GROUND PAD)
PIN PAD
Figure 6. P.C. Assembly for Exposed Pad Thermal Release Path – Side View (drawing not to scale
IDT™ / ICS™ 3.3V LVPECL ZERO DELAY CLOCK GENERATOR
14
ICS8735AM-21 REV. A JULY 31, 2008