ics8535ag-21t Integrated Device Technology, ics8535ag-21t Datasheet - Page 9

• Manufacturer Part Number: ics8535ag-21t
• Description: Low Skew, 1-to-4 Lvcmos-to-3.3v Lvpecl Fanout Buffer
• Manufacturer: Integrated Device Technology

VFQFN EPAD T
In order to maximize both the removal of heat from the package
and the electrical perfor mance, a land patter n 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 3. 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”)
IDT
ICS8535BI-01
LOW SKEW, 1-to-4 LVCMOS/LVTTL-TO-3.3V LVPECL FANOUT BUFFER
™
/ ICS
™
3.3V LVPECL FANOUT BUFFER
F
IGURE
PIN PAD
HERMAL
3. P.C.A
PIN
SSEMBLY FOR
R
ELEASE
SOLDER
GROUND PLANE
P
E
ATH
XPOSED
P
AD
EXPOSED HEAT SLUG
T
THERMAL VIA
HERMAL
9
R
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.
ELEASE
P
ATH
–S
LAND PATTERN
(GROUND PAD)
IDE
SOLDER
V
IEW
(D
ICS8535BGI-01 REV. B JANUARY 8, 2008
RAWING NOT TO
PIN
PIN PAD
S
CALE
PRELIMINARY
)