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2-3 Low-temperature lead-free solder pastes（138℃）

2-3-1 Product Characteristics:

1）Adopt lead-free environment-protection alloy and meet the RoHS directive.
   
 2）New Technical support, special chemical formula, provide with favorable wettability to make up for poor wettability of lead-free alloy to ensure high reliability.
 
 3）Little residue after reflowing which has no corrosion and good electrical insulation. 
 
 4）Adopt high-efficiency thixotropic agent to prevent subseidence as preheating and printing. 
 
 5）Meet the American standard of ANSI/J-STD-004 flux (ROLO).
 
 6）The diameter of tin powder is accurately controlled between 25μm to 45μm, and the flux is specifically made to insure continuously printing and fine pattern.
 
 7）Advanced moisture-keeping technology and persistent viscidity ( viscosity above 48 hours), more than 8 hours of valid working life.
 
 8）The residue is clear and has little influence to test.
 
 9）Light soldered point and other excellent performance.

2-3-2 Designation, Melting Point and Alloy Compositions

2-3-3 WH-138G-M (Sn42Bi58) Shelf Management:

1) Store the paste between 4℃ to 8℃ is the best.It will take at least 0 hours to re-warm from refrigerator to room temperature.
   
 2) Churn up the paste before use. It will take 5min by automatic churning machine and 10min by hand.
 
 3) In use at any time to ensure that only opened a bottle of paste. Guarantee at any time in the production of fresh solder paste is used to reduce the negative impact of the environment. Has openings for the solder paste, tightly covered when not in use inside and outside the cover. Solder paste to prevent drying or oxidation, to extend the service life of solder paste.
 
 4) Use the paste according to the principle of FIFO.
 
 5) Make sure the paste rolling continuously when printing, and the height 1/2 equal to 3/4of the scraper’s. Initial monitoring of the viscosity of solder paste. Smooth rolling can be omitted to make a better printed solder paste to the stencil opening, more beautiful graphics.
 
 6) Transfer the PCB with paste on to the next procedure as soon as possible(within 1 hour). Solder paste to prevent drying, viscosity change and maintain the viscous.
 
 7) Don’t leave the paste on PCB more than 1 hour to avoid jam on PCB. 
 
 8) Collect the used paste with a new vessel.Old solder paste to avoid the impact of the new solder paste . Storage used by the light of paste solder paste storage conditions. Mix up the used paste and fresh paste by 1:3, and the used paste can be refined as the fresh one. 
 
 9）Attention: Please read the MSDS before operation. Avoid contacting the paste by skin and clothes. If contacted, sweep off the paste by solvent with alcohol in. Avoid inbreathing vapor from reflowing. Wash hands after soldering operation. 

2-3-4 WH-138G-M (Sn42Bi58) Screen Print Parameters

Stainless steel or rubber,with a shore scleroscope hardness of above 80-90
   
 Print Speed： as fast as to 150mm/s
 
 Wettability and Temperature ：less than 60% RH at 22-28oC

2-3-5 WH-138G-M Sn42Bi58 Reflow Profile

Parameters for temperature profile

1）The highest haetaing rate is 2.5℃/s in pre-heating zone. Rising over fast will cause tin-balling.
   
 2）Keep the temperature. In the range of 150-210℃ and the temp. rise no bigger than 2.5 degree/s during the soaking zone, which lasts regularly from 60 s to 90 s. 
 
 3）The peak temperature. In the reflowing zone changes in the range of 225℃ to　255℃. It will stay for from 40 s to 70 s over 217℃.
 
 4）The cooling rate applied in the cooling segement must be less than 4℃/s.

Additional: The curve should be made according to shape of the plate and function of the devices. The circumstance parameter is suggested to be 25±2℃ by temperature. And 45-65% by humidity