CY7C65640A Datasheet, PDF (19/21 Pages) Cypress Semiconductor – TetraHub™ High-Speed USB Hub Controller

16.0 Package Diagram
The TetraHub is available in a space-saving 56-pin QFN (8 × 8 mm)
Figure 16-1. 56-Lead QFN 8 x 8 MM LF56A
CY7C65640A
51-85144 *F
Note. The bottom metal pad size varies by product due to die
size variable. If metal pad design or dimension are critical with
your board designs, please contact a Cypress Sales office to
get the specific outline option.
16.1 Quad Flat Package No Leads (QFN) Package
Design Notes
The QFN (Quad Flatpack No Leads), being a lead free
package, the electrical contact of the part to the Printed Circuit
Board (PCB) is made by soldering the lands on the bottom
surface of the package to the PCB. Hence special attention is
required to the heat transfer area below the package to provide
a good thermal bond to the circuit board. A Copper (Cu) fill
should be designed into the PCB as a thermal pad under the
package. Heat is transferred from the TetraHub through the
device’s metal paddle on the bottom side of the package. Heat
from here is conducted to the PCB at the thermal pad. It is then
conducted from the thermal pad to the PCB inner ground plane
by a 5 x 5 array of via. A via is a plated through-hole in the PCB
with a finished diameter of 13 mil. The QFN’s metal die paddle
must be soldered to the PCB’s thermal pad. Solder mask is
placed on the board top side over each via to resist solder flow
into the via. The mask on the top side also minimizes
outgassing during the solder reflow process.
Please follow the layout guidelines provided in the PCB layout
files accompanied with the CY4602 TetraHub Reference
Design Kit. The information in this section was derived from
the original application note by the package vendor. For further
information on this package design please refer to the appli-
cation note “Surface Mount Assembly of AMKOR’s
MicroLeadFrame (MLF) Technology”. This application note
Document #: 38-08019 Rev. *I
Page 19 of 21
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