RMA-155 Solder Paste - SAC305, T4 (88.5 Percent), 600g Cartridge
RMA-155 Solder Paste for Military, Aviation, and Medical Applications
RMA-155 Solder Paste was designed to offer a balanced performance, making it ideal for high-complexity boards with a variety of component sizes. Compatible with both SnPb and SAC alloys, RMA-155 delivers consistent transfer efficiencies, excellent response-to-pause, and a strong oxidation barrier, even for long and hot profiles. It is halogen-free, resists graping (even on small components and tiny deposits), prevents head-in-pillow, and minimizes voiding for BGAs and large thermal planes (QFNs).
RMA-155 solder paste conforms to the RMA classification for QQ-S0571F and offers proven performance similar to Indium’s best-in-class, award-winning Pb-free solder pastes.
Alloys
Indium Corporation manufactures low-oxide spherical powder composed of a variety of Pb-free alloys that cover a broad range of melting temperatures. Types 4 and 3 powders are standard offerings with SAC alloys. The metal load is the weight percent of the solder powder in the solder paste and is dependent upon the powder type, alloy, and application.
Storage
Refrigerated storage will prolong the shelf life of solder paste. The shelf life of RMA-155 is 6 months when stored at <10°C. Solder paste packaged in cartridges should be stored tip down.
Solder paste should be allowed to reach ambient working temperature prior to use. Generally, the paste should be removed from refrigeration at least 2 hours before use. The 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 the 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 of stencil aperture has significantly reduced or eliminated 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 20 mil 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).
- For optimum transfer efficiency and release of the solder paste from the stencil apertures, industry-standard aperture and aspect ratios should be adhered to.
Cleaning
RMA-155 is designed to be reliable without needing to be cleaned. However, the flux can be removed, if necessary, by using a commercially available flux residue remover (i.e., semi-aqueous, solvent-based, or vapor degreaser).
Stencil cleaning is best performed using isopropyl alcohol (IPA) as a solvent. Most commercially available stencil cleaners also work well.
Compatible Products
- Rework Flux: TACFlux 020B, TACFlux 089HF
- Cored Wire: CW-807
- Wave Flux: WF-7745, WF-9945