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Reflow temperature curve

1, the higher the melting point of a sharp narrowing of the process window, tin-lead solder has a melting point is 183 ° C, its complete liquefaction temperature of 205 ° C to -215 ° C, while the printed circuit board of the temperature limit of 230 ° C -240 ° C, the existing process margin of 15 ° C to -35 ° C; commonly used lead-free solder melting point is 217 ° C to -220 ° C, the complete liquefaction temperature of 225 ° C to -235 ° C, the PCB board temperature limit has not changed, the process margin narrowed to 5 ° C to -15 ° C, narrow process margin requirements the reflow oven now with high repeat accuracy, as well as with a tight board temperature difference.
2, liquefaction time lengthened: the traditional lead solder paste liquefaction time of 40s-60s; liquefaction time is generally of lead-free solder paste
60s-90s.
The following is the difference of the two lead-free reflow profile with traditional leaded solder paste curve.


FIG ① is a graph of the typical lead.
Guarantee liquefaction time and liquefaction temperature can be seen from Figure (2) there must be a high peak temperature of about 260 ° C, PCB board and component which is bound to cause thermal shock or damage.
Solution:
Preheating temperature constant flux before ① melting tin;
(2) use two or more heating temperature zone to do welding temperature zone;
③ independent temperature reduced in size, while increasing the number of heating zones, easy to process adjustments;
④ the same production capacity as far as possible to reduce the overall dimensions of the heating zone, in order to reduce oxidation;
(5) recommended the use of nitrogen protection technology (non-essential);

⑥ new design of the intermediate support means to reduce the deviation of the distribution of the intermediate support means becomes large. Mingzhandaohang: nsk imported bearings skf bearings timken bearings


                                     
Several commonly used lead-free substitute

Alloy solder paste application: 96,5 Sn / 3,5 Ag melting point of 221 ° C to 95,5 Sn / 4,0 Ag / 0,5 Cu melting point of 217 ° C.
2, alloy solder wave soldering and hand soldering applications: 99,3 Sa / 0,7 Cu melting point of 227 ° C.
(Terms of materials, several new solder paste has been put on the market, but can not replace the existing lead-tin solder, they all need to make process adjustments, new solder paste is the main difference with respect to traditional solder paste melting point is relatively commonly used lead-free solder paste typically have a melting point of 217 ° C to -225 ° C)


                                              
Lead substitute requirements
Price: Many vendors are required to price can not exceed 63Sn/37Pn, but finished lead-free alternatives than 63Sn/37Pb high 35%.
2, melting point: Most manufacturers require a minimum of 150 ° C solidus temperature to meet the work requirements of the electronic equipment. The liquidus temperature depending on the application.
The Wave soldering electrode: for successful wave soldering, liquid temperature should be lower than 265 ° C.
The manual welding solder wire: liquid temperature should be lower than the soldering iron operating temperature 345 ° C.
Solder paste: The liquidus temperature should be lower than 250 ° C.
3, the conductive.
4, good thermal conductivity.
5, the smaller the range of solid-liquid coexistence: most of the experts suggested that this temperature range is controlled at 10 ℃, in order to form a good solder joint solidification range is too wide, it is possible to solder joint cracking occurs, the electronic products premature damaged.
6, low toxicity: alloy composition must be non-toxic.
7, has a good wettability.
8, good physical properties (strength, tensile, fatigue Tuberculosis): alloy must be able to to provide Sn63/Pb37 attainable strength and reliability, and not by the device on the projection angle welds.
9, production repeatability and consistency of the solder: As the electronic assembly process is a high-volume manufacturing process, requiring the repeatability and consistency to maintain a high level, if certain alloy composition is not in bulk conditions under repetitive manufacturing, or its melting point in the mass production of larger changes due to the change of the ingredients, it can not be taken into account.
10 Joint Appearance: solder joint appearance with the appearance of the tin / lead solder should be close.
11, supply capacity.
12, compatibility with lead: the short term will not immediately be transferred to a lead-free system, so the lead may still be used in PCB pads and component terminals, such as doped solder such as drill, may cause the solder alloy lowering the melting point is very low, the intensity is greatly reduced.


                                                     
Why lead-free process
Lead is a toxic heavy metal body excessive absorption of lead can cause poisoning, ingestion of low levels of lead may impact on human intelligence, nervous system and reproductive system, the global electronics assembly industry annually consumes about 60,000 tons solder, but also increased year by year the lead salt thus formed industrial waste causes serious environmental pollution, thus reducing the use of lead has become the focus of the world, many large companies in Europe, Japan is vigorously accelerate the development of alloys lead-free alternatives and planning began in 2002 in the assembly of electronic products to gradually reduce the use of lead. 2004 completely eliminated. (Traditional solder composition 63Sn/37Pb, in the electronic assembly industry, Pb is widely used). Mingzhandaohang: nsk imported bearings skf bearings timken bearings


                                     
Nuo Sida Shenzhen Technology Co., Ltd. Technical Support


Nuo Sida, Shenzhen Science and Technology Co., Ltd. was established in 1993, the company specializes in producing fully automatic screen printing presses, ive soldering, wave soldering, reflow, SMT peripheral equipment. Nuo Sida brand wave soldering share in the domestic high volume, with more than 10 years of experience to serve our customers. Fully automatic screen printer vigorously after several years of development, has reached the international advanced level, following the DEK, MPM after one pair of fully automatic screen printer R & D, production has the experience and the strength of the manufacturer. NSP3000 fully automatic screen printer is the emphasis on high-speed, repeatability and flexibility excellent platform for high-volume applications including fine pitch QFP, SOP, BGA, CSP, 0402,0201, high-density electronic components provide high accuracy The degree of mass imaging operation.

The ive peak after two years of development and testing, the indicators have reached the international level to address the traditional ive soldering capacity issues. Truly high-volume production requirements, while addressing the precision welding and modular design, with equipment upgrades requirements. When upgrading production more than one combination into a production line to achieve greater production capacity.

      
Adhering to the "high-tech, high-quality, excellent service," the purpose, adhere to international standardization, professional approach, Nuo Sidas lead-free wave soldering, lead-free reflow has been successfully exported to the United States, Japan, Korea, Singapore, Malaysia, Indonesia, Thailand, Brazil and other countries, and there is an agency Nuo Sida products with good quality and good service customers alike.

"Customer is God" is the Nuo Sidas aim has always been sincere to provide customers with the highest quality equipment and superior after-sales service. We would like to work together to progress, brilliant. Mingzhandaohang: nsk imported bearings skf bearings timken bearings

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