ICS858020 Datasheet, PDF (10/14 Pages) Integrated Device Technology – LOW SKEW, 1-TO-4 DIFFERENTIAL-TO-CML FANOUT BUFFER

ICS858020
LOW SKEW, 1-TO-4
DIFFERENTIAL-TO-CML FANOUT BUFFER
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
4. 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, refer to the
Application Note on the Surface Mount Assembly of Amkor’s
Thermally/Electrically Enhance Leadfame Base Package,
Amkor Technology.
SOLDER
PIN
EXPOSED HEAT SLUG
S OL D ER
PIN
PIN PAD
GROUND PLANE
THERMAL VIA
LAND PATTERN
(GROUND PAD)
PIN PAD
FIGURE 4. P.C.ASSEMBLY FOR EXPOSED PAD THERMAL RELEASE PATH –SIDE VIEW (DRAWING NOT TO SCALE)
858020AK
10
REV. A DECEMBER 10, 2007