Fluxes and solder pastes are specially engineered materials formulated with various applications in mind. The differences in the chemical formulations are such so that specific characteristics of a flux or solder paste can be achieved. You may require ultra-low or near zero residue amounts after reflow, or an enhanced oxygen barrier formulation to solve issues such as HiP or graping, or a formulation specifically for fine powders such as type 6 or type 7 for SiP pastes.
These are just a few examples of common requests which need very different flux/paste formulations. Due to the differences in formulations, the behaviour of different products can vary. Other characteristics that are likely to vary are the material lifetimes, the shelf life, floor life etc. We at Indium have found that different customers have different naming conventions for the various lifetimes and this prompted Dr Andy Mackie to write the following blog post which includes a table showing how we refer to the different material lifetimes…
https://www.indium.com/blog/materials-lifetimes-a-modest-proposal.php
To achieve the optimum performance from a flux or solder paste it is important that the material lifetimes are understood and also that you know what the recommendations of the manufacturer are. Recommendations are made based on material testing and experience and should be considered as a strong guideline. Please refer to the product technical data sheets which can be found on the Indium website www.indium.com or contact the Indium technical support team at askus@indium.com with any questions regarding lifetimes or any other technical queries.