Viscosity and tack are two important material properties that define a flux. People often “tack” them together as one, thinking they go hand-in-hand. Typically, this is the case, but not always. This blog discusses the differences between these properties.
The different flux and solder paste formulations mean that some products will have different material lifetimes than others. Understanding the lifetimes and following manufacturers recommendations can help to ensure you get the optimum performance from the material.
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Since the post solder residues of types R and RMA fluxes are considered non-corrosive, non-conductive and non-hydroscopic, flux removal is not usually necessary. If cleaning is desired this is best accomplished with a commercially available flux residue remover.
Best practice is to always remove RA residues in electronics applications.
Standard Packaging
These liquid soldering fluxes are packaged in 2 different size plastic containers:
1 U.S. pint (0.473 liter)
1 U.S. gallon (3.785 liter)
NC-506 Flux
Features
Suitable for Pin-Grid Array and standard Ball Grid Array applications
Excellent solderability to all common surface metallizations
No-clean residue
Can be used for printing, dipping, and pin transfer deposition
Offers high yields in BGA bumping process
Suitable for both Pb-Free or SnPb applications
Introduction
Ball Attach Flux NC-506 is a low viscosity thixotropic no-clean flux designed for use in ball attachment to substrates (BGA manufacturing). It is especially useful in applications requiring soldering to surface finishes with tenacious oxides, such as nickel. It can also be used wherever a no-clean ball attach flux is needed, and is suitable for a variety of different deposition methods.
Properties
Value
Test Method
Flux type Classification:
ROL1
J-STD-004 (IPC-TM-650: 2.3.32 and 2.3.33)
Typical Viscosity:
320kcps
Brookfield HB DVII+ -CP (5rpm)
SIR (ohms, post cleaning):
Pass (>109 after 7 days @ 85ºC & 85% RH)
J-STD-004 (IPC-TM-650: 2.6.3.3 IPC-B-24
Typical Acid Value:
103mg KOH/g
Titration
Typical Tack Strength:
250g
J-STD-005 (IPC-TM-650: 2.4.44)
Shelf Life:
6 months (-20°C to +5°C)*
Viscosity change / microscope examination
All information is for reference only. Not to be used as incoming product specifications.
WS-366 Interconnect Flux
Benefits
Excellent cleanability, residue can be removed with room temperature water
Can be used for printing, dipping, and pin transfer deposition
Offers high yields in BGA bumping process
Excellent solderability
Wide process window
Suitable for SnPb, Pb-Free, and high lead-containing applications
Designed for Flip-Chip applications
Introduction
WS-366 Interconnect Flux is a high viscosity paste-type flux designed for use in BGA bumping and board level attachment. It can also be used wherever a water-soluble flux with excellent cleanability is desired.
Properties
Flux type Classification:
H1
Color:
Amber to brown
Stencil Life:
>8 hours at room temperature
Shelf Life:
3 months at 0 to +30 °C
SIR (ohms, post cleaning):
Pass (>109 after 7 days @ 85ºC & 85% RH)
Typical Viscosity:
Brookfield:
425kcps at 5rpm
Halide Content:
<3% Cl equivalent
Acid Value:
30-50
Tack Strength:
100-400g
All information is for reference only. Not to be used as incoming product specifications.
Fluxless Soldering
Some applications are very sensitive to the use of a flux due to the post reflow residue that may be present. Also, flux may be a problem in a vacuum environment or in an application in which it must be free of corrosive or volatile materials.
If gold is used for the outer metalization on the parts to be joined, acceptable wetting may be possible without the use of a flux. If this is not possible, a reducing atmosphere may be used to remove the oxides and result in sufficient wetting. Below are suggestions and helpful hints for choosing a reducing atmosphere that fits your application.
The higher the reflow temperature the more effective the oxidation removal using a reducing atmosphere. A reflow temperature that is 350°C and above is the best for oxide removal.
Nitrogen or argon is sometimes used in fluxless soldering because it prevents the formation of oxides during reflow. However, these gases do not remove preexisting oxides on the metalization, only the hydrogen can do that.
Fluxless soldering is also used when joining the two substrates together where flux residue would be detrimental to the operation of the final product. For example, voiding due to flux entrapment can result in poor performance because of reduced electrical or thermal conductivity.
In an application where a reducing atmosphere is not practical, two or more metalizations can be joined using flux in the initial pre-coating of the substrates. After precoating is complete, the flux residue can be removed using an appropriate solvent. The cleaned parts can then be assembled without a flux and reflowed a final time to join them. This method is especially effective when fairly large pieces need to be joined and flux entrapment can not be tolerated.
Proven in PV module assembly processes, Indium Corporation's No-Clean Liquid Solar Tabbing Fluxes are non-corrosive, non-conductive, and provide excellent solderability on all types of silver metallizations. Formulated to provide a wide process window, Indium Corporation's Liquid Solar Photovoltaic Fluxes are compatible with Pb-Free and tin-lead alloys.
Liquid Tabbing Flux Product Specifications
Specifically developed for tabbing and stringing applications, Indium Corporation's Liquid Solar Fluxes work in popular module assembly processes utilizing conduction reflow, IR reflow, and convection reflow. Ideal for module assembly processes where high throughput is a necessity and minimum flux residue is a key requirement, Indium Corporation's line of Liquid Tabbing Flux provides excellent solderability on all type of metallizations.
