AN1923 Motorola / Freescale Semiconductor, AN1923 Datasheet - Page 2

• Manufacturer Part Number: AN1923
• Description: AN1923 Application Note Mounting Method with Mechanical Fasteners for the MRF19090 and Similar Packages
• Manufacturer: Motorola / Freescale Semiconductor

ASSEMBLY
component in a board assembly involves the stackup
tolerance of the completed system.
tolerances for the seating plane height of the component are
expected to be
can be kept to
component will sit. In the assemblies built for the power life
test, the recess in the copper pallet was machined to a depth
dimension such 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
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0.005 . Achievable tolerance of the PCB thickness is
A challenging aspect of high volume manufacturing of any
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0.007 . The tolerance for the cavity depth
0.003 in the recessed area where the
Figure 5. Component Fixture Used for Reflow
Figure 4. Direction of the Lead Deflection
Achievable device
MOTOROLA SEMICONDUCTOR APPLICATION INFORMATION
the lead deflection should always be toward the backside of
the 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, 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. The PCB, device and
solder reflow fixture can be assembled to a pallet or a reflow
boat for the solder reflow step.
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