AN1908 Freescale Semiconductor / Motorola, AN1908 Datasheet - Page 2

• Manufacturer Part Number: AN1908
• Description: Solder Mounting Method for the MRF19090S and Similar Packages
• Manufacturer: Freescale Semiconductor / Motorola

ASSEMBLY
component in a board assembly involves the stack–up
tolerance of the completed system.
tolerances for the seating plane height of the component are
tolerances of the copper can be kept to
recessed area where the component will sit. In the assemblies
built for the power life test, the recess in the copper pallet was
machined so that the device leads would be assembled with
a maximum lead tip deflection of 0.015 . The direction of the
lead deflection is important in controlling stresses on the
component and the solder joint. Figure 4 illustrates how the
lead deflection should always be toward the backside of the
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AN1908
0.005 . Achievable tolerances of the PCB are 0.007 . The
A challenging aspect of high volume manufacturing of any
2
Î Î Î Î Î Î Î Î Î
1.360
1.220
1.160
PCB
.200
.140
.000
Copper Pallet
Lead
Freescale Semiconductor, Inc.
For More Information On This Product,
Figure 5. Component Fixture Used for Reflow
4X ø
Figure 4. Direction of the Lead Deflection
Achievable device
ø.188
.120
0.003 in the
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.12
Clamp, Python Earless
Material: Glass Silicone (G–7)
MOTOROLA SEMICONDUCTOR APPLICATION INFORMATION
component. A fixture was used to deflect the leads at the tip
so they were in contact with the solder. This solder reflow
fixture also held the component in place during reflow. The
fixture used for this assembly is depicted in Figure 5. To solder
multiple components at one time, a simple fixture can be
designed to secure all of the components during the reflow
operation. Although the solder fixture used in the reflow of the
power cycling boards was screw mounted, this can be done
with several techniques—for example, using an array of pins.
All soldering is accomplished in one pass using 62/36/2
Sn/Pb/Ag and/or 63/37 Sn/Pb solder.
provide a structurally and electrically adequate solder fillet at
the drain and gate leads, as well as a void–free solder joint at
the source contact for good thermal and electrical performance.
4X BREAK EDGE 0.005
The soldering process and fixturing must be designed to
.190
2X .009
Î Î Î Î Î Î Î Î Î
Direction of Deflection
.580
.390
0 to 15 mils
2X .090