V048K020T080 Datasheet, PDF (13/15 Pages) Vicor Corporation – VI Chip - VTM Voltage Transformation Module

Application Note (continued)
PRELIMINARY
V•I Chip Soldering Recommendations
V•I Chip modules are intended for reflow soldering processes.
The following information defines the processing conditions
required for successful attachment of a V•I Chip to a PCB.
Failure to follow the recommendations provided can result in
aesthetic or functional failure of the module.
Inspection
For the BGA-version, a visual examination of the post-reflow
solder joints should show relatively columnar solder joints with
no bridges. An inspection using x-ray equipment can be done,
but the module’s materials may make imaging difficult.
Storage
V•I Chip modules are currently rated at MSL 5. Exposure to
ambient conditions for more than 72 hours requires a 24 hour
bake at 125ºC to remove moisture from the package.
Solder Paste Stencil Design
Solder paste is recommended for a number of reasons, including
overcoming minor solder sphere co-planarity issues as well as
simpler integration into overall SMD process.
63/37 SnPb, either no-clean or water-washable, solder paste
should be used. Pb-free development is underway.
The recommended stencil thickness is 6 mils. The apertures
should be 20 mils in diameter for the In-Board (BGA)
application and 0.9-0.9:1 for the On-Board (J-Leaded).
The J-Lead version’s solder joints should conform to IPC 12.2
• Properly Wetted Fillet must be evident
• Heel fillet height must exceed lead thickness plus solder thickness.
Removal and Rework
V•I Chip modules can be removed from PCBs using special tools
such as those made by Air-Vac. These tools heat a very localized
region of the board with a hot gas while applying a tensile force
to the component (using vacuum). Prior to component heating
and removal, the entire board sho©uld be heated to 80-100ºC to
decrease the component heating time as well as local PCB
warping. If there are adjacent moisture-sensitive components, a
125ºC bake should be used prior to component removal to
prevent popcorning. V•I Chip modules should not be expected to
survive a removal operation.
Pick & Place
In-Board (BGA) modules should be placed as accurately as
possible to minimize any skewing of the solder joint; a maximum
offset of 10 mils is allowable. On-Board (J-Leaded) modules
should be placed within ±5 mils.
To maintain placement position, the modules should not be
subjected to acceleration greater than 500 in/sec² prior to reflow.
Reflow
There are two temperatures critical to the reflow process; the
solder joint temperature and the module’s case temperature. The
solder joint’s temperature should reach at least 220ºC, with a
time above liquidus (183ºC) of ~30 seconds.
The module’s case temperature must not exceed 208 ºC at
anytime during reflow.
239
183
165
degC
91
Joint Temperature, 220ºC
Case Temperature, 208ºC
16
Soldering Time
Figure 25—Thermal profile diagram
Because of the ∆T needed between the pin and the case, a forced-
air convection oven is preferred for reflow soldering. This
reflow method generally transfers heat from the PCB to the
solder joint. The module’s large mass also reduces its
temperature rise. Care should be taken to prevent smaller
devices from excessive temperatures. Reflow of modules onto a
PCB using Air-Vac-type equipment is not recommended due to
the high temperature the module will experience.
Vicor Corporation
Tel: [phone]
vicorpower.com
Figure 26— Properly reflowed V•I Chip J-Lead.
V•I Chip Voltage Transformation Module V048K020T080 Rev. 1.2 Page 13 of 15