Kester 951 Data Sheet

®

951

951

Low-Solids No-Clean Liquid Flux

Low-Solids No-Clean Liquid Flux

Product Description

Kester 951 is a halogen-free, non-rosin organic
flux designed for wave soldering conventional and
surface mount circuit board assemblies. The
extremely low solids content (2.0%) and nature of
the activator system results in practically
NO RESIDUE left on the assembly after soldering.
Boards are dry and cosmetically clean as they exit
the wave solder machine. There are no residues
to interfere with electrical testing. Kester 951
exhibits improved soldering performance to
minimize solder bridges (shorts) and excessive
solder defects. This flux is suitable for automotive,
computer, telecommunications and other
applications where reliability considerations are
critical. The surface insulation resistance on
soldered boards is higher than that provided by
typical organic water-soluble fluxes. Kester 951
contains a corrosion inhibitor such that no
corrosion products are formed when bare copper
surfaces are exposed to humid environments.

Performance Characteristics:

• Improves soldering performance

• Eliminates the need and expense of cleaning

• Non-corrosive tack-free residues

• Classified as ORL0 per J-STD-004

• Compliant to Bellcore GR-78

Physical Properties

Specific Gravity: 0.814 ± 0.003

Antoine Paar DMA 35 @ 25°C

Percent Solids (theoretical): 2.0

Acid Number: 14.3 mg KOH/g of flux

Tested by potentiometric titration

Thinner: 110

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 951 PD

Day 1

Day 4

Day 7

2.3 ´ 1010W 9.4 ´ 109W

1.3 ´ 1010W 7.8 ´ 109 W

9.8 ´ 109W 6.3 ´ 109W

951 PU

8.2 ´ 109W

7.5 ´ 109W

5.8 ´ 109W

951

Application Notes

Flux Application:

Kester 951 can be applied to circuit boards by a spray, foam or dip process. Flux deposition should be

2

120-240 mg of solids/cm
remove excess flux from the circuit board and prevent dripping on the preheater surface.

Process Considerations:

The optimum preheat temperature for most circuit assemblies is 93-110°C (200-230°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 solvent, 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 solvent evaporation.

Flux Control:

Acid number is normally the most reliable method to control the flux concentration of low solids, no-clean
fluxes. To check concentration, a simple acid-base titration should be used. PS-22 Test Kit and procedure
are available from Kester. Control of the flux in the foam flux tank during use is necessary for assurance of
consistent flux distribution on the circuit boards. The complex nature of the solvent system for the flux makes
it imperative that Kester 110 Thinner be used to replace evaporative losses. When excessive debris from
circuit boards, such as board fibers and from the air line build up in the flux tank, these particulates will redeposit
on the circuit boards which may create a build up of residues on probe test pins. It is, therefore, necessary
to clean the tank and then replenish it with fresh flux when excessive debris accumulates in the flux tank.

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

Cleaning:

Kester 951 flux residues are non-conductive, non-corrosive and do not require removal in most applications.

Storage and Shelf Life:

Kester 951 is flammable. Store away from sources of ignition. Shelf life is 1 year from date of manufacture
when handled properly and held at 10-25°C (50-77°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 West 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 Yokokawau 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