61 No Clean Tacky Flux

BOW ELECTRONIC SOLDER
TECHNICAL BULLETIN
BOW # 61
NO CLEAN TACKY FLUX

Description :

Bow 61 is a no clean tack flux that is specifically formulated for use in all BGA and CSP applications. This product is a flux of the RMA type (mildly activated wood rosin). Bow 61 features high tack and provides excellent wetting to a variety of surfaces. This flux will remain tacky for 48 hours and can be reflowed in either air or N2. Bow 61 leaves a clear residue that needs no solvent cleaning.

Application Recommendations:

Stencil Printing:
Typical printing protocols for solder pastes apply. Contact printing with the stencil thickness being equivalent to the desired flux deposit should be used. Metal squeegees should be used to minimize scooping. Attack angles of 45°C are optimal. Stencil life of eight hours can be obtained if the ambient conditions are controlled to below 25°C and relative humidity between 40 and 60%.

Dip Application:
Bumps should be dipped to 0.5 mils or slightly less to transfer sufficient volume. Flux depth on the applicator should be set to allow for enough flux to be present to compensate for the maximum variability of bump height on the chip to leave the minimum deposit on the smallest bump. Flux depth should also be maintained to keep flux a minimum of 1.0 mil from the chip surface to avoid flux creep on the die surface. Applicator life of 8 hours can be achieved if the ambient conditions are maintained below 25°C and relative humidity between 40 and 60%.

Reflow Parameters:
Most conventional reflow equipment can be utilized with either air or N2 atmosphere. Standard reflow profile for bulk soldering is adequate, with preheats that promote even temperature distribution across the board or component. Temperatures at least 20°C above liquidus should be achieved with the time above liquidus being maintained for 30 to 60 seconds.

Storage and Shelf Life:
Six months shelf life is guaranteed if stored in a dry environment with temperatures between 5 and 25°C in their original sealed package. Storage for periods longer than 2 months should be done at temperatures between 5 and 10°C to insure that minimal separation takes place in the package. Syringes should be stored tip down. Used material should not be returned to its original container after being used to avoid contamination and shelf life issues.

Physical Properties
% Solids	49.0 +/-0.5%
Viscosity @ 25°C	10 to 20 Kcps
Peak Tac Force	4.1 g/mm2
Density	0.9 +/-0.5 g/ml
1Haake PK100 viscometer, PQ 1B sensor @ 13.6 S1 2IPC TM-650-2.4.44

Residue Properties:
Flux Activity1	LO
SIR1	>1x108 Ohms
SIR2	>2x104 Megaohms
Electromigration2	Pass
Copper Mirror1	Pass
CI-/Br_ (AgCrO4)	Pass
1IPC J-STD-004 2Bellcore TR-NWT-000078 Issue