Indium Corporation manufactures low-oxide spherical powder composed of a variety of Pb-Free alloys that cover a broad range of melting temperatures. Type 3 powder is the standard offering with SnAgCu, SnAg, and SnSb Pb-free alloy systems. The metal percent is the weight percent of the solder powder in the solder paste and is dependent upon the powder type and application.
Refrigerated storage will prolong the shelf life of solder paste. The shelf life of Indium3.2 is no less than 4 months when stored at <5°. Solder paste packaged in cartridges and syringes should be stored tip down.
When refrigerated, solder paste should be allowed to reach ambient working temperatures prior to use. Generally, paste should be removed from refrigeration at least 2 hours before use. Actual time to reach thermal equilibrium will vary with the container size, and the solder paste temperature should be verified before use. Jars and cartridges should be labeled with the date and time of opening. It is not recommended to remove worked paste from the stencil and mix it with the unused paste in the jar because this may alter the rheology of the unused paste.
Stencil Design:
Electroformed and laser cut/electropolished stencils produce the best printing characteristics among stencil types. Stencil aperture design is a crucial step in optimizing the print process. The following are a few general recommendations:
| Solder Paste Bead Size | 20–40mm in diameter |
| Print Speed | 150mm/second |
| Squeegee Pressure | 0.018–0.027kg/mm of blade length |
| Underside Stencil Wipe | Start at once per every 5 prints and decrease frequency until optimum value is determined |
| Solder Paste Stencil Life | >12 hours (<60% RH and 22–28°C) |