858020AK

10

REV. A DECEMBER 10, 2007

ICS858020

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.

THERMAL VIA

LAND PATTERN

SOLDER

PIN

SOLDER

PIN PAD

PIN PAD

PIN

GROUND PLANE

EXPOSED HEAT SLUG

(GROUND PAD)