AD9854ASQ Analog Devices Inc, AD9854ASQ Datasheet - Page 41

• Manufacturer Part Number: AD9854ASQ
• Manufacturer: Analog Devices Inc

Specifications of AD9854ASQ

• Lead Free Status / RoHS Status: Not Compliant

THERMALLY ENHANCED PACKAGE MOUNTING GUIDELINES
This section provides general recommendations for mounting
the AD9854ASQ (the thermally enhanced exposed heat sink
package) to printed circuit boards. The exceptional thermal
characteristics of this package depend entirely on proper
mechanical attachment.
Figure 64 shows the package from the bottom and the dimen-
sions of the exposed heat sink. A solid conduit of solder must be
established between this pad and the surface of the PCB.
Figure 65 depicts a general PCB land pattern for an exposed
heat sink device. Note that this pattern is for a 64-lead, not an
80-lead, device, but the relative shapes and dimensions still
apply. In this land pattern, a solid copper plane exists inside the
individual lands for device leads. Also, the solder mask opening
is conservatively dimensioned to avoid any assembly problems.
Figure 64. Package Bottom and Exposed Heat Sink
Figure 65. General PCB Land Pattern
10mm
SOLDER MASK
OPENING
THERMAL LAND
14mm
Rev. D | Page 41 of 52
The thermal land itself must be able to distribute heat to an
even larger copper plane, such as an internal ground plane.
Vias must be uniformly provided over the entire thermal pad
to connect to this internal plane. A proposed via pattern is
shown in Figure 66. Via holes should be small (12 mil, 0.3 mm)
so that they can be plated and plugged. These holes provide the
mechanical conduit for heat transfer.
Finally, a proposed stencil design is shown in Figure 67 for
screen solder placement. Note that if vias are not plugged,
wicking occurs, which displaces solder away from the exposed
heat sink, and the necessary mechanical bond is not established.
Figure 67. Proposed Stencil Design for Screen Solder Placement
Figure 66. Proposed Via Pattern
AD9854