Kester 979 Data Sheet

®

979

979

VOC-Free No-Clean Liquid Flux

VOC-Free No-Clean Liquid Flux

For Lead-bearing and Lead-free alloys

For Lead-bearing and Lead-free alloys

Product Description

Kester 979 is a VOC-free, no-clean flux formulation
for high quality, low-defect soldering of electronic
circuit board assemblies. This flux's finely tuned
activation system offers the best wetting available
in VOC-Free liquid flux technology and the shiniest
solder joints. Kester 979 also reduces micro
solderballing on glossy laminates and between
connector pins. Kester 979 will not attack properly
cured solder masks or FR-4 Epoxy-Glass
laminate. Kester 979 leaves a minimal amount of
residue after soldering. All remaining residues are
non-corrosive, non-conductive and do not need to
be removed.

Performance Characteristics:

• Biodegradable at pH of 2.0 or greater

• Chemically compatible with most solder masks
and board laminates

• Does not degrade Surface Insulation

Resistance

• No offensive odors

• Bright, shiny solder connections

• Classified as ORL0 per J-STD-004

• Compliant to Bellcore GR-78

Physical Properties

Specific Gravity: 1.020 ± 0.010

Antoine Paar DMA 35 @ 25°C

Percent Solids (typical): 4.5

Tested to J-STD-004, IPC-TM-650, Method 2.3.34

Acid Number: 40.0 ± 3.0 mg KOH/g of flux

Tested to J-STD-004, IPC-TM-650, Method 2.3.13

Thinner: DI Water

Reliability Properties

Copper Mirror Corrosion: Low

Tested to J-STD-004, IPC-TM-650, Method 2.3.32

Corrosion Test: Low

Tested to J-STD-004, IPC-TM-650, Method 2.6.15

Silver Chromate: Pass

Tested to J-STD-004, IPC-TM-650, Method 2.3.33

Chloride and Bromides: None Detected

Tested to J-STD-004, IPC-TM-650, Method 2.3.35

Fluorides by Spot Test: Pass

Tested to J-STD-004, IPC-TM-650, Method 2.3.35.1

SIR, IPC (typical): Pass

Tested to J-STD-004, IPC-TM-650, Method 2.6.3.3

Blank 979 PD

Day 1

Day 4

Day 7

2.8 ´1010W 1.9 ´ 1010W

1.5 ´1010W 1.1 ´ 1010W

1.2 ´1010W 9.1 ´ 109W

979 PU

2.3 ´ 1010W

1.2 ´ 1010W

9.6 ´ 109W

979

Application Notes

Flux Application:

Kester 979 can be applied to circuit boards by a spray or dip process. Flux deposition should be 120-240 mg

2

of solids/cm
flux from the circuit board and prevent dripping on the preheater surface.

Process Considerations:

The optimum preheat temperature for most circuit assemblies is 95-115°C (203-239°F) as measured on the
top or component side of the printed circuit board. Dwell time in the wave is typically 2-4 seconds. The wave
soldering speed should be adjusted to accomplish proper preheating and evaporate excess water, which
could cause spattering. For best results, speeds of 1.1-1.8 m/min (3½-6 ft/min) are used. The surface tension
has been adjusted to help the flux form a thin film on the board surface allowing rapid water evaporation.

Elimination of Splattering:

Since VOC-free fluxes are water-based, splattering can be a problem. Splattering occurs when water comes
in contact with molten solder, so it may be necessary to use forced air to drive off the water. Manufacturers
have reported that blowing hot air at 0.28-0.85 m3/hr (10-30 ft3/hr) greatly assists in drying the water off the
circuit boards.

Flux Control:

Acid number is normally the most reliable method to control the flux concentration of low solids, no clean
fluxes. Evaporative loss is minimal because this flux is water-based. To check concentration, a simple
acid-base titration should be used. PS-20 Test Kit and procedure are available from Kester.

(750-1500 mg of solids/in2). An air knife after the flux tank is recommended to remove excess

Cleaning:

Kester 979 flux residues are non-conductive, non-corrosive and do not require removal in most applications.
If residue removal is required, plain DI water at 43-54°C (110-130°F) may be used.

Storage and Shelf Life:

Because this formulation is water based, it is subject to freezing. A minimum storage temperature of 4°C
(40°F) is recommended. If frozen, the Kester 979 is easily reconstituted by stirring at room temperature.
Shelf life is 1 year from date of manufacture when handled properly and held at 4-25°C (40-77°F).

Health & Safety:

This product, during handling or use, may be hazardous to health or the environment. Read the Material
Safety Data Sheet and warning label before using this product.

World Headquarters: 800 W. Thorndale Avenue, Itasca, Illinois, 60143 USA

Phone: [phone] • Email: [e-mail] • Website: www.kester.com

Asia Pacific Headquarters

500 Chai Chee Lane

Singapore 469024

([phone]

[e-mail]

European Headquarters

Zum Plom 5

08541 Neuensalz

Germany

([phone]

[e-mail]

Japanese Headquarters

20-11 Yokokawa 2-Chome

Sumida-Ku

Tokyo 130-0003 Japan

([phone]

[e-mail]

The data recommendations presented are based on tests, which we consider reliable. Because Kester has no control over the conditions of use, we disclaim any responsibility connected with the
use of any of our products or the information presented. We advise that all chemical products be used only by or under the direction of technically qualified personnel who are aware of the poten­tial hazards involved and the necessity for reasonable care in their handling. The technical information contained herein is consistent with the properties of this material but should not be used in
the preparation of specifications as it is intended for reference only. For assistance in preparing specifications, please contact your local Kester office for details.

Rev: 22Mar10