Appendix C TRF3762 QFN Installation Using a Hakko Hot Air Rework Station
C.1
USEFUL LINKS
Appendix C
www.ti.com
The TRF3762 devices are optionally sampled separately from the board (TRF3671EVM-X). This guideline
is designed to help the person evaluating these parts to install the sample device on the board provided.
The EVM board has an immersion gold plating. Due to gold leaching into the solder joint, it is a best
practice to tin the pads and wick off the extra solder. Using a solder with silver content helps but is
unnecessary.
Apply solder paste to each pad including the center ground; do not skimp when applying paste to the
center ground. It is recommended to use a type 6 Sn62Pb36Ag2 alloy with an 82% loading in an EFD
dispensing system; solder paste can be applied manually with a dental pick.
Under a microscope, place the device inside the square silkscreen labeled U2. Pin 1 of the device is
designated by a round dot on the package; pin 1 on the board is designated by an asterisk and a slightly
mitered corner.
Use a tool like a dental pick or the point of a hobby knife (like an X-ACTO™ knife) to position the part so
that the device leads are centered on the traces. The solder paste may smear; this is not an issue at this
point.
Place the board in the Hakko Omnivise, and position it over the Hakko preheater. With the preheater set
at 200
°
C, let the part heat up for 30 seconds. Place the Hakko hot air nozzle (A1130, this is a 0,44-mm
diameter nozzle) over the device. With the temperature set at 343
°
C and the air flow set at 15
liters/minute, turn on the hot air rework station. This setting can be adjusted lower if adjacent components
are being disturbed. Letting the board thermally soak over the preheater along with letting the hot air come
up to temperature while blowing on the part provides a thermal ramp profile. This helps to ensure a good
solder joint.
Watch the device as it heats up; when the solder paste reflows, let the part continue to heat for 15
seconds. Remove it from the heat. Inspect the part immediately, and verify that there are no solder shorts
and that there is connection at all pins. A soldering iron with a tip radius of 0.008 at 370
°
C works well for
this; add extra flux when doing rework.
To clean the flux residue from the board: spray the board with a flux cleaner, lay a thin absorbent tissue
over the board, and brush the board through the tissue. The absorbent tissue wicks up the
flux-contaminated solvent. Blow the board dry with compressed air. If spurs are present, additional
cleaning in an ultrasonic cleaner and subsequent baking may be necessary.
Hakko Products:
http://www.hakkousa.com/2006/default_1.asp?Assistant=Dinky
Solder Paste, Flux, Dispenser:
http://www.efd-inc.com/mikros/index.html
http://www.efdsolder.com/
12
TRF3762 QFN Installation Using a Hakko Hot Air Rework Station
SLWU056 – June 2008
