Solder Connection

Solutions in Soldering Technology

WS-820 Water Soluble Solder Paste

ALPHA® WS-820 is a lead free, halide free, solder paste, offering the ideal combination of printability and reflow profile process window with excellent cleanability in a lead free alloy solder paste. 

Formulated to meet the requirements of water soluble solder lead free applications, and it was developed to  increase the reflow profile window of WS-819, while offering exceptional post reflow cleanability and low BGA voiding.  

This paste is designed to enable users of WS-609, WS-709 and WS-809 and other leading water soluble paste brands to comply with RoHS and customer based demand for lead free materials.

Key Products Features & Benefits:

  • Excellent print volume and print volume repeatability down to 12 mil (0.3mm) features.
  • Able to spread and wet using straight ramp or soak reflow profiles in air.
  • High spread/wetting lead free paste compatible with lead free alloys and surface finishes.
  • High Reflow Yield with IPC Class II Voiding Performance when used to solder BGA components.
  • Excellent wetting characteristics on all common surface finishes (including Entek HT OSP). JIS Spread 88.6% on Entek HT OSP. 
  • Cleanable with water based cleaning systems.
  • J-STD Classification: ORH0


Product Number : WS820

Prod. No. 153515
WS820 SAC305 T3 500GM POT

Data Sheets and Info

Health & Safety

Technical Bulletin

Product Guide

ROHS Certificate


Q - What is colophony and can it cause any health issues?
A - Colophony is a generic term for rosin, this is the sap or sticky substance that derives from pine and spruce trees. Its "stickiness" lends itself to being used in a wide range of products. We have traditionally used this product in fluxes due to these specific properties it can however lead to breathing difficulties and skin sensitivity. Always use fume filtration when soldering and change filters regularly.

Q - What is the difference between rosins and resins?
A - The terms are often used interchangeably, but rosin is a naturally occurring substance, and resin is either a modified rosin or completely synthetic material. Rosins are plant based products and are subject to more natural variation than resins, however resins are commonly used in newer flux formulations due to their more consistent performance.

Q - Do I need to change my printing process when I go to finer printing from size 3 to size 4 paste?
A - Generally when changing from T3 to T4 there is not much difference in printing setup. Depending upon the paste used you may have to make slight adjustments to print parameters such as release speed as aperture fill is greater with finer powders on small apertures but this is just to optimise the print as you would do when changing any paste. It’s by no means certain you will need to do this but it may give you further benefits.

Q - Do I need to change my printing process when I go to Ultra Fine printing from size 4 to size 5 paste?
A - The biggest change will be going to PS5 and its not so much the printing parameters changing but the stencils are invariably a lot thinner and so you need good support and setup such as making sure you have a release distance of 3 mm set (the distance over which release speed is controlled as the stencil acts more like a drum skin) I would also run with the minimum pressure to avoid stencil damage (coining) this is as most PS stencils are <100µm typically 75µm in thickness. It’s not as bad with PS4 as most stencils are in the 100µm or slightly above range and are more robust.

In all cases (can’t really think of an exception) smaller powder sizes go hand in hand with printing smaller features. Smaller features as we approach Area Ratio 0.66 and in some cases people try to/do operate in the region of AR 0.6-0.66 mean that the printing process has to be good, you have to “respect the fundamentals” i.e. board support, calibration of such things as print height, squeegee condition, decent PCB quality, registration etc.

Again more a feature of small apertures rather than the powder size of paste itself you may need to look at what is your maximum ‘abandon’ time with any paste if you run a start stop process and work to it i.e. don’t exceed and use automatic under screen cleaning where needed. Smaller apertures tend to ‘clog’ more readily and so may need a more frequent aperture clean regime.

Associated Products

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