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V•I Chip Voltage Transformation Module

V048K160T015

Rev. 1.0

Page 13 of 15

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.

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 Inboard (BGA) application and 0.9-0.9:1 for

the Onboard (J-Leaded).

Pick and place

Inboard (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. Onboard (J-Leaded) modules should be placed

within ±5 mils.

To maintain placement position, the modules should not be subjected

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.

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.

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.

The J-Lead versions 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 should 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.

Case Temperature, 208ºC

Joint Temperature, 220ºC

239

165

91

16

degC

183

Soldering Time

Figure 24—Thermal profile diagram

Figure 25— Properly reflowed V•I Chip J-Lead