ISL8204M Ver la hoja de datos (PDF) - Intersil
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ISL8204M Datasheet PDF : 20 Pages
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ISL8204M, ISL8206M
Thermal Vias
A grid of 1.0mm to 1.2mm pitch thermal vias, which
drops down and connects to buried copper plane(s),
should be placed under the thermal land. The vias should
be about 0.3mm to 0.33mm in diameter with the barrel
plated to about 1.0 ounce copper. Although adding more
vias (by decreasing via pitch) will improve the thermal
performance, diminishing returns will be seen as more
and more vias are added. Simply use as many vias as
practical for the thermal land size and your board design
rules allow.
Stencil Pattern Design
Reflowed solder joints on the perimeter I/O lands should
have about a 50µm to 75µm (2mil to 3mil) standoff
height. The solder paste stencil design is the first step in
developing optimized, reliable solder joints. Stencil
aperture size to land size ratio should typically be 1:1. The
aperture width may be reduced slightly to help prevent
solder bridging between adjacent I/O lands. To reduce
solder paste volume on the larger thermal lands, it is
recommended that an array of smaller apertures be used
instead of one large aperture. It is recommended that the
stencil printing area cover 50% to 80% of the PCB layout
pattern. A typical solder stencil pattern is shown in the
Package Outline Drawing L15.15x15 on page 19. The gap
width between pad to pad is 0.6mm. The user should
consider the symmetry of the whole stencil pattern when
designing its pads. A laser cut, stainless steel stencil with
electropolished trapezoidal walls is recommended.
Electropolishing “smooths” the aperture walls resulting in
reduced surface friction and better paste release which
reduces voids. Using a trapezoidal section aperture (TSA)
also promotes paste release and forms a "brick like" paste
deposit that assists in firm component placement. A
0.1mm to 0.15mm stencil thickness is recommended for
this large pitch (1.3mm) QFN.
Reflow Parameters
Due to the low mount height of the QFN, "No Clean" Type 3
solder paste per ANSI/J-STD-00 is recommended. Nitrogen
purge is also recommended during reflow. A system board
reflow profile depends on the thermal mass of the entire
populated board, so it is not practical to define a specific
soldering profile just for the QFN. The profile given in
Figure 30 is provided as a guideline, to be customized for
varying manufacturing practices and applications.
300
250
PEAK TEMPERATURE +230°C~+245°C;
KEEP ABOUT 30s ABOVE +220°C
200
SLOW RAMP AND
SOAK FROM +100°C TO
150 +180°C FOR 90s~120s
100
50
RAMP RATE ≤1.5°C FROM +70°C TO +90°C
0
0
100
150
200 250
300 350
DURATION (s)
FIGURE 30. TYPICAL REFLOW PROFILE
17
FN6999.1
February 25, 2010
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