AN1908 Freescale Semiconductor / Motorola, AN1908 Datasheet

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AN1908

Manufacturer Part Number
AN1908
Description
Solder Mounting Method for the MRF19090S and Similar Packages
Manufacturer
Freescale Semiconductor / Motorola
Datasheet
1.AN1908.pdf (8 pages)
MOTOROLA
SEMICONDUCTOR APPLICATION NOTE
Solder Mounting Method for the MRF19090S
and Similar Packages
Prepared by: Wendi Stemmons, Jerry Mason, Rich Wetz, Tom Woods, Mahesh Shah and David Runton
INTRODUCTION
method for a 90–Watt power device.
methodology is recommended for any ceramic/metal flange
device with similar materials and construction (copper
tungsten flange with ceramic insulator and Alloy–42 leads)
and up to 90 Watts of RF output power. This mounting method
involves soldering the CuW flange to a heatsink with the leads
soldered to a printed circuit board (PCB). Critical elements
that must be carefully addressed are mechanical stress of the
assembly and thermal management. The mounting method
described has adequately taken these issues into account. A
power life test evaluation was done as verification.
operates at 1.9 GHz with 90 Watts of output power. Similar
devices operate between 1.8 to 2.1 GHz with 90 Watts of output
power.
MOUNTING METHOD
solder mount assembly line with device leads solder attached
to a PCB and the flange soldered to a copper pallet. The
pallets were bolted to fan–cooled, finned aluminum heatsinks
with thermal compound on the interface. Power life testing
was done at a specific duty cycle and heatsink temperature.
REV 0
MOTOROLA SEMICONDUCTOR APPLICATION INFORMATION
The following document describes a solder mounting
Figure 1 shows the MRF19090S power transistor. This device
Assemblies of the new design were built in an automated
Motorola, Inc. 2001
Figure 2. MRF19090S 90–Watt Power Device
MRF19090S
Component
Board Construction
Freescale Semiconductor, Inc.
For More Information On This Product,
This mounting
Solder Preform
Go to: www.freescale.com
Copper Pallet
PCB
Assembly construction of a pallet with this device is shown in
Figure 2. Configuration of the pallets onto the aluminum
chassis is shown in Figure 3.
Figure 3. Full Assembly of Power Life Test
Figure 1. MRF19090S Power Transistor
Order this document
AN1908
by AN1908/D
1

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AN1908 Summary of contents

Page 1

... This mounting Figure 1. MRF19090S Power Transistor Assembly construction of a pallet with this device is shown in Figure 2. Configuration of the pallets onto the aluminum chassis is shown in Figure 3. Solder Preform PCB Copper Pallet Figure 3. Full Assembly of Power Life Test Go to: www.freescale.com Order this document by AN1908/D AN1908 1 ...

Page 2

... Freescale Semiconductor, Inc. AN1908 ASSEMBLY A challenging aspect of high volume manufacturing of any component in a board assembly involves the stack–up tolerance of the completed system. tolerances for the seating plane height of the component are 0.005 . Achievable tolerances of the PCB are 0.007 . The tolerances of the copper can be kept to recessed area where the component will sit ...

Page 3

... An actual board assembly used for the power life test is shown in Figure 9. 250 200 150 Solder Pad 100 mils minimum 0 0 Figure 7. Typical Solder Reflow Profile Go to: www.freescale.com AN1908 Maximum time above 150 C is 5.5 100 200 300 Time (seconds) for Sn/Pb/Ag Solder 3 ...

Page 4

... Freescale Semiconductor, Inc. AN1908 SCREEN PRINT SOLDER PASTE PLACE DEVICE FLANGE IN THE SLOT WITH LEADS OVER SOLDER PASTE SOLDER REFLOW IN CONVECTION REMOVE REUSABLE REFLOW THERMAL COMPOUND TO BACK Figure 8. Process Flow for Board Assembly For More Information On This Product MIL THICK STAINLESS STENCIL ...

Page 5

... The devices were powered at a 50% duty cycle for 2000 cycles, representing 1000 hours of cycling. Dissipated Power vs Time (One Cycle) Die Junction 175 TIME (MINUTES) Go to: www.freescale.com AN1908 of 0.65 C/W. Based plus the interface resistance. JC Power Die Junction at Room Temperature 5 ...

Page 6

... Freescale Semiconductor, Inc. AN1908 Lead and solder joint temperatures were measured on several PCBs using a scanning infrared microscope after the power cycling. Lead temperatures were found to be approximately 135 Watts of power dissipation and sink temperature. Figure 11 displays an image taken from the infrared microscope. Following the power life testing, solder joints were visually inspected and found to have no cracks after 2000 cycles ...

Page 7

... Freescale Semiconductor, Inc. For More Information On This Product, MOTOROLA SEMICONDUCTOR APPLICATION INFORMATION NOTES Go to: www.freescale.com AN1908 7 ...

Page 8

... ASIA/PACIFIC: Motorola Semiconductors H.K. Ltd.; Silicon Harbour Centre, 2 Dai King Street, Tai Po Industrial Estate, Tai Po, N.T., Hong Kong. 852–26668334 Technical Information Center: 1–800–521–6274 HOME PAGE: http://www.motorola.com/semiconductors/ For More Information On This Product, 8 are registered trademarks of Motorola, Inc. Motorola, Inc Equal MOTOROLA SEMICONDUCTOR APPLICATION INFORMATION Go to: www.freescale.com AN1908/D ...

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