The definition of lead-free

◆The toxicity of lead

The U.S. environmental protection agency (epa) : lead and its compounds are 17 kinds of serious damage to human life and natural environment is one of the chemicals; Lead in industrial waste by groundwater system into the animal or human food chain; In the human body excessive amounts of lead will cause nerve disorders, developmental delays, hemoglobin and regeneration system to reduce and cause anemia and high blood pressure; The occupational safety and health administration (osha) standards: adult should be lower than 50 mg/dl, blood lead levels in children's blood lead levels should be lower than 30 mg/dl.

◆The definition of lead-free

So far there is no international general definition; Can be reference standard: pipe welding lead in solder and flux should be lower than 0.2 wt % (USA), 0.1 wt % (Europe); International standard organization (iso) proposal: electronic combination of lead solder alloy should be less than 0.1 wt %.

◆The development of lead-free solder process

In 1991 and 1993: the United States senate "Reid bill", put forward requirements of electronic solders will lead control under 0.1%, American industry strong opposition, died;

Nemi since 1991, the NCMS, nist, dit, NPL, pcif, itri, jiep organization on lead-free solder research, such as consumption could exceed $20 million, is still in continue;

In 1998: Japanese consumer electronics method, driving business development lead-free electronic products;

In 1998: Japanese consumer electronics method, driving business development lead-free electronic products;

January 2000: nemi lead-free solder, recommended to the industry standardization of sn - 3.9 - ag - 0.6 - cu for reflow soldering, sn - 0.7 - cu or sn - 3.5 ag for wave soldering;

June 2000: the United States ipc lead - free roadmap published version 4, suggested in 2001 by American business utilizing electronic products, implement comprehensive utilizing in 2004;

August 2000: Japan jeita lead - free roadmap published version 1.3, corporate Japan suggest standardize lead-free electronics assembly in 2003;

In January 2002, the eu's lead - free roadmap1.0 edition published, according to the results of the questionnaire survey to the industry to provide important statistics about utilizing;

On February 13, 2003, the European parliament and the European Union ministers meeting organization, formally approved the directive effect of weee and rohs, force since July 1st, 2006, sales of electronic products in the European market must be lead-free electronic products; Individual types of electronic products (except temporarily)

In March 2003, the ministry of information industry for the pollution prevention and control measures for the administration of electronic information products production, proposed since July 1, 2006 on the market of the national key regulatory electronic products not contain pb within the directory.

Three aspects to choose the most appropriate flux

For users, select flux is not the more expensive the better, more is not well-known manufacturers must be good, the key question is "to choose to suit their own product characteristics and process characteristics of flux", according to the flux of the research and development and promotion experience for many years, according to the selection of flux problem, summarizes the three persons experience for inside and outside of reference:

1. Combined with product selection flux.

The grade of the product itself and the characteristics of the product itself, is the first consideration when choosing flux condition, high-grade products, such as computer motherboard, boards and other computer peripheral products such as the motherboard or high precision products, generally choose high grade no clean flux, there are a few customer use cleaning type flux welding again after cleaning, useful solvent cleaning type type water flux. Such a high grade product, no matter be a choice from cleaning flux and the flux, first of all to ensure that after welding can be *, because in the plate when the condition is good, generally on the flux of the tin is not too big a problem, and residue or the existence of residual ion, the biggest hidden danger is the inner product. We suggest that such products choose high-grade no clean flux, the flux activity of moderate, residues after welding, ion condition residues can be controlled in 1.5 mu gnacl/cm2, greatly strengthened the comparability of products after welding. If not very at ease, with no clean solder flux can also choose to clean type, after welding cleaning it is currently in one of the most used in electronic assemblies; If you need to choose clean type flux, in order to promote environmental protection cause, we suggest the customer to choose water flux, the flux welding effect is good, easy to clean after welding, high after cleaning can let a guest * sex more at ease.

Best in class products can choose not to or containing halogen containing halogen rarely low solid content from cleaning flux, such as high-end motherboard of telephone, a CD player, choose such flux, plate surface is bright and clean, the residue after welding is less, do not contain halogen or rarely halogen basic can guarantee the electrical properties after welding, general won't cause problems such as leakage or electrical interference.

Lower class electronic products, generally plank is poorer, more for single bare copper or precoating board, if you choose high-grade no clean without residual flux, welding effect may be poor, on the other hand, may be because of the damaged board face the original coating white phenomenon. This case we suggest prednisone scent flux activity will be selected, while the plate after welding residual is more, but the effect of tin and * can be guaranteed.

At present, online materials, transformers, coils and small chip (SMD) transformer components such as pin tin plating, most customers choose no clean flux, at the request of the customers from cleaning, we recommend no clean with no residue containing rosin flux, the flux activity is moderate, the tin effect is good, no residue after welding, component pin will not cause corrosion, another bright spot is smooth, and has good wettability, the solder can meet most customers want "climb" effect.

To sum up, in combination with product selection flux, is to fully understand the characteristics of their products, including the grade of the product, the situation of the circuit board, components of pin from several aspects such as comprehensive consideration, and then select the suitable for their own product of flux.

2. According to the requirements of customers choose flux.

Most in choosing flux will be put forward to the customer's requirements, particularly electronic products suppliers or factory of OEM brand, its customers or the inspection is more strict in this respect, some manufacturers can not meet the requirements to produce their own or has the certain difficulty, but the product outgoing to contract, but to ask for the same or higher conditions. Common customer requirements are the following several aspects:

(1). Tin solder on full. This is more than 90% of the guests will ask request, tin solder to full activity must choose appropriate, good wettability flux.

(2). The plate no residue or white phenomenon. Customer facing such a demand, most vendors will choose no clean flux, if caused by plate problem white after welding, after welding cleaning solution to optional.

(3). The bright spot. 63/37 article tin welding of solder joints under normal circumstances are relatively light, if the content of tin is low or impurity levels of solder joints is relatively not so bright; The average flux solder joint will not cause the effect of extinction, unless is extinction type flux; Rosin flux than excluding rosin flux solder joints is relatively light, if add the bright spot in the flux, solder joint will be more bright after welding.

(4). Wuxi beads, even welding or virtual welding, welding and other adverse conditions. These conditions is a typical bad in the electronic welding, general vendors will have to compare the strict detection and control, has studied the quality management knows that such a slogan "is a good product to instead of the inspection", this sentence tell us, if we can in the condition of poor control of welding process, will be more important than do again after repair. To ensure good quality in the production, the correct selection of flux is important, because we have been analyzed, on these bad could and flux are related. Therefore, select the activity, good wettability flux, coupled with a good process to cooperate, is fundamental to avoid these adverse factors.

(5). No leakage and so on poor performance. If the customer have such request, try not to choose highly reactive flux or halogen content is higher, if the plate shape must use such flux, we can through the solution for cleaning, if because of the cost of cleaning or considering the requirements of environmental protection, under the condition of the products, and other conditions permit, select water flux is also a good way.

Above mainly electronics assemblies processing enterprises as an example to discuss, such manufacturers of finished product is the circuit board processing completed, without looking like a finished product machine, so, when the guest can directly for inspection solder joints; If after completion of welding and assembly of finished products manufacturers, the guests are seldom open the casing to test welding, and this time, we should consciously manufacturer's own internal strengthen quality control, after welding assembly process, can be used more than customer's request, to require its own process, welding process, because we all know that "the process is the process of the customer", only every moment, every little bit, continuously strengthen the qualities of our products will be able to progress and improve.

3. Choose flux according to equipment and process conditions.

Equipment status, determines the status of the welding process, the process is a key link in the process of choosing flux; Is a simple example, if the spray wave oven choose rosin flux, may be not appropriate, because of high solid content in a relatively short period of time, it is possible to block spray nozzle; If it is foaming wave soldering chose only suitable to spray flux, foaming effect is not so good. According to the equipment and process condition choose flux has the following several aspects:

(1). Manually tin furnace.

Manual when soldering tin furnace, flux with foaming and foaming two cases, rarely see manual spray when mass production. When not foaming, can choose the flux range is wide; Have a foaming process, we should choose foam flux with better effect, both manual and automatic welding, we on foaming better standards are the same, the first: the bubble to small, not too big; Second: the bubble size uniform; Third: foam as far as possible some more lasting.

Because no preheating process manual tin stove, some do not contain no clean with no residue of rosin flux, we generally do not recommend to the customer, use of such a flux with beads, and other harmful may; If the customer must insist on such flux, we suggest or try again after confirmed.

(2) foaming wave soldering furnace.

Foaming wave furnace must choose foam type flux, currently besides rosin flux foaming effect is better, no clean with no residue and no clean low residual flux foaming problem has been solved, as for the criteria of foam has been discussed above.

(3). Spray wave soldering furnace.

Spray wave furnace in addition to the flux of rosin content is higher, the selection of flux sort is more, if you can choose not to contain no clean of rosin flux effect will be better. At present, some no clean flux can foam can spray, for such process select flux will not have too big problem.

(4). The double wave soldering furnace.

Double wave soldering furnace mainly for the production of tiles and plug-in conventional circuit board, at this point, the circuit board welding surface before and after the need to pass two peaks; The first wave is higher (also called takanami or turbulence), main effect is to weld, make preliminary fixed element; The second wave is relatively flat (also called flat or rectifier wave), mainly for plastic solder joints. In the process, often encounter the problem is, flux, when after the first wave of the activator or wetting agent and so on have been fully decomposed, so in the second wave, the flux has actually does not work, at this time appear easily even adverse conditions such as welding, icicles. In order to solve this situation, we suggest customers to use a slightly higher solid content, activator and wetting agent to withstand heat flux; Manufacturer and flux in order to solve such a problem, often added in the flux distribution of the activator and wetting agents, to make the flux to withstand different temperature section, after the first wave of welding can still play the role of the run-off.

Category: professional knowledge