• Alloy: Sn63/Pb37
• Type 3 powder (90 percent metal load)
• Quantity: 600g cartridge
• Wide reflow process window
• Consistent fine-pitch print deposition

RMA-SMQ51A is a rosin-based, mildly activated, air reflow, solder paste ideally suited for high speed assembly processes. Due to RMA-SMQ51A’s high tack value and exceptional tack endurance, placement machines can run at full speed. In addition, its wide processing window allows it to be used with standard eutectic Sn/Pb, Sn/Pb/Ag, and high-temperature alloys including Au/Sn, Pb/Sn, and Pb/Sn/Ag.

RMA-SMQ51A prints ultrafine-pitch with full and consistent deposition. Excellent wetting is observed with OSP, Au/Ni, and HASL metallizations.

Alloys

Indium Corporation manufactures low-oxide spherical powder composed of Sn/Pb and Sn/Pb/Ag in a standard Type 3 mesh size. Other non-standard mesh sizes are available upon request. The weight ratio of the flux/vehicle to the solder powder is referred to as the metal load and is typically in the range of 83–92% for standard alloy compositions.

Storage and Handling Procedures

Refrigerated storage will prolong the shelf life of solder paste. The shelf life of RMA-SMQ51A is 6 months when stored at <10°C. Storage temperatures should not exceed 25°C. When storing solder paste contained in syringes and cartridges, they should be stored tip down.

Solder paste should be allowed to reach ambient working temperature 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 container size. Paste temperature should be verified before use. Jars and cartridges should be labeled with date and time of opening.

Printing

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:

• Discrete components—A 10–20% reduction in stencil aperture area may significantly reduce or eliminate the occurrence of mid-chip solder beads. The “home plate” design is a common method for achieving this reduction.
• Fine-pitch components—A surface area reduction is recommended for apertures of 20mil pitch and finer. This reduction will help minimize solder balling and bridging that can lead to electrical shorts. The amount of reduction necessary is process-dependent (5–15% is common).
• A minimum aspect ratio of 1:5 is suggested for adequate release of solder paste from stencil apertures. The aspect ratio is defined as the width of the aperture divided by the thickness of the stencil.

Cleaning

RMA-SMQ51A meets no-clean requirements. The flux can be removed, if necessary, by using a commercially available flux residue remover.

Stencil Cleaning: This is best performed using an automated stencil cleaning system for both stencil and misprint cleaning to prevent extraneous solder balls. Most commercially available stencil cleaning formulations including isopropyl alcohol (IPA) work well.

Compatible Products

Rework Flux: TACFlux 007