• Quantity: 1 Gallon
• Meets the requirements of J-STD-004 Type ROL0
• More heat-stable than rosin-free formulas
• More active than most other no-clean formulas
• Wide process window for soldering larger and/or thick circuit boards

WF-9940 is Indium Corporation’s most active and heat-stable low-solids rosin-containing no-clean wave solder flux. WF-9940 was developed to meet the original requirements of J-STD-004 as a ROL0 and for effectively soldering through-hole and mixed-technology assemblies. It performs well with both tin-lead and lead-free solders. WF-9940 is very heat-stable and well-suited for selective soldering applications. With strong soldering performance, WF-9940 passes all common reliability requirements. It is non-corrosive and does not contribute to detrimental circuit board insulation resistance degradation or electrochemical migration.

Physical Properties

As received, Indium Corporation’s WF-9940 flux is light amber in color. This amber color is a result of more than one-half of the 3.63% flux solids being composed of amber-colored rosin or rosin derivatives. The balance of the flux is an anhydrous alcohol and aliphatic hydrocarbon blend having a flash point of 54°C. This solvent blend ensures an even distribution of flux solids both during storage and during spray flux deposition. The specific gravity of WF-9940—0.795 at 25°C—is measurably higher than that of pure isopropyl alcohol. However, in contrast to higher solids content fluxes, specific gravity is not the best method to quality control WF-9940. This is because flux solids content is relatively low and small amounts of water contamination can confuse specific gravity measurements. While in-process quality control of WF-9940 is not generally required, the best method to ensure both solids content and activity level is by acid value titration.

Indium Corporation Compatible Products

• Solder Paste: Indium8.9 or Indium10.1
• Cored Wire: CW-807, CW-808, Core 230-RC
• Flux Pen: FP-500 (rosin-containing)

Indium Corporation’s wave soldering fluxes have been designed to be fully compatible with Indium solder paste, cored wire, and rework flux, and are also expected to be compatible with many of Indium’s competitors’ products. For example, WF-9940 Wave Solder Flux is not only compatible with Indium8.9HF Solder Paste, but also with our 5.8LS, 8.9 series, 92 series, and 10 series. Indium Corporation determines compatibility primarily by matching flux chemistry. However, a select number of the wave, reflow, and rework product combinations have been thoroughly tested to ensure that the combined flux residues meet the electrical and reliability requirements of IPC J-STD-004

The J-STD-004 copper mirror test is performed per IPC-TM-650 method 2.3.32. To be classified as an “L” type flux, there should be no complete removal of the mirror surface. WF-9940 shows no complete removal of the copper mirror and, therefore, is classified as a ROL0.

Copper corrosion is tested per IPC-TM-650 method 2.6.15. This test gives an indication of any visible reactions that take place between the flux residue after soldering and copper surface finishes. In particular, green copper corrosion (formed as copper-chloride) should not be seen.

Surface Insulation Resistance (SIR) Test Data

The Surface Insulation Resistance test is performed per IPC-TM-650 Method 2.6.3.3, using boards prepared per IPC-TM-650 Method 2.6.3.3. All boards soldered with WF-9940 pass the requirements of having exhibited no dendritic growth, no visible corrosion, and a minimum insulation resistance of 100 megohms (1 x 108 ). The values shown on the two adjacent graphs show the number of Ohms times ten to the power of the vertical axis. The IPC-TM-650 SIR is a 7-day test and gives a general idea of the effect of the flux residue on the electrical properties of the surface of the circuit board.

Electromigration (ECM) Test Data

The electromigration test is performed to IPC-TM-650 method 2.6.14.1 with boards prepared using IPC-TM-650 method 2.6.3.3. The test conditions for this test are 496 hours at 65°C ± 2°C and 88.5% ± 3.5% RH. To pass this test, there should be no visible corrosion and no dendritic growth that decreases line spacing by more than 20%. In addition, the insulation resistance should not drop more than one order of magnitude after the first 96-hour stabilization period when a bias voltage is applied.

Shelf Life

The shelf life for this product is 2 years in an unopened container stored at less than 32.2°C (90°F). Shelf life for an opened container will vary depending on storage conditions, including open time, temperature, and humidity. For the longest shelf life of an opened container, replace the cap to reduce alcohol evaporation and store it in a cool, dry environment.

Residue Removal Recommendations

All of Indium Corporation’s no-clean fluxes, including this formula, are designed to be electrically safe under normal consumer electronic and telecommunication operating conditions. Unless otherwise specified, electrically safe means that the post-soldering residues pass J-STD-004 SIR and ECM testing. However, it is understood that some customers desire to remove residues for cosmetic reasons, improved in-circuit testing, improved compatibility with specific conformal coatings, or where the operating parameters of the circuit board may be in extreme conditions for a prolonged period.

If the removal of no-clean flux residues is desired, the most commercially available cleaning agents will be effective. Indium Corporation’s Technical Support Engineers work closely with cleaning agent vendors and have confirmed flux residue removal capabilities from several vendors using their recommended products and parameters. It is unlikely that users of Indium Corporation’s no-clean products will need to change their current residue removal materials and parameters from those currently used.