Description:
WS353 water soluble solder paste has been developed in response to electronics manufacturers demand for an all-purpose, reliably consistent water-soluble solder paste. WS353 offers extended stencil life and tack time, robust environmental tolerance and printing characteristics, excellent activity, a broad cleaning process window, and compatibility with both tin-lead and lead-free solder alloys. WS353 can be used in fine pitch printing applications and
has proven effective in the assembly of 0201 components. WS353 provides consistent printing characteristics and slump resistance during high-speed printing. The excellent activity of WS353 makes it a suitable choice when soldering to standard or difficult-to-wet parts, including lead-free alloys and finishes. In addition, WS353 has proven to substantially reduce voiding under micro-BGAs. The residues of WS353 may be cleaned easily in straight water, with the result being exceptional electrical reliability. In addition, WS353 is designed to not foam during washing, even in high-pressure wash systems.
Features:
- Broad Printing Process Window
- Excellent Wetting
- Easily Cleaned Residues
- Lengthy Stencil Life and Tack Time
- Reduces Voiding Under BGAs
- Low Foaming during Washing
- Halide-Free
Handling and Storage:
WS353 has a refrigerated shelf life of 6 months at 4° C (40° F) - Allow the solder paste to warm up completely and naturally to ambient temperature (8 hrs.) prior to breaking the seal for use. Do not force warm. - Mix the product lightly and thoroughly (1-2 mins. max) to ensure even distribution of any separated material - Do not store new and used paste in the same container, and reseal any opened containers while not in use. - Replace the internal plug and cap of the 500 gram jars to ensure the best possible seal.
Paste Application:
Apply sufficient paste to the stencil to allow a smooth, even roll during the print cycle (a bead diameter of ½ to 5/8 inch is normally sufficient to begin.) - Apply small amounts of fresh solder paste to the stencil at controlled intervals to maintain paste chemistry and workable properties. WS353 provides the necessary tack time/force for today’s high-speed placement equipment. - Ensuring proper support of PCBs during assembly and handling will enhance product performance and reliability.
Printing:
- Snap-off distance = on contact (0.00”)
- PCB Separation Distance = .030-.100”
- PCB Separation Speed = Slow-Medium
- Squeegee Pressure =1-1.7lbs/ In. of blade
- Print Speed .5 – 4 inches per sec
Cleaning:
WS353 can be cleaned easily with normal tap water. Deionized water is recommended for the final rinse. A temperature of less than 120° F is sufficient for removing residues. An in-line or other pressurized spray cleaning system is suggested, but is not required.
Paste Tech Tips: Problems and Possible Causes:
- Bridging - excessive solder, pad component solder ability, alignment
- Solder Balls - low preheat temperature, oxidized or excess paste, too rapid initial ramp up
- Tomb Stoning - excessive delta temperature, rapid heat rate, component to pad mismatch, paste registration
- Discolored Joints - excessive peak temperature, board paste component contamination, excessive soak time
- White Residue - solder paste oxidation, excessive time at temperature
- Beading - excess solder paste, component placement
- Leaching - excessive reflow time or temperature
Reflow Profile (Sn/Ag/Cu):
RTS Profile Guidelines:
- The typical rate of rise for the RTS profile is .9 – 1.2°C/
- The profile should be a straight line or concave; it should
- Peak temperature is 235 - 245° C. Time above liquidus is 45 ± 15. The total profile length should be between 2.5 – 3.5 minutes
- Cool down should be controlled within 4° C/second.
