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Third, the formation of tin slag:
1 >, static molten solder oxidation
According to the theory of liquid metal oxidation, oxygen will be strongly adsorbed on the surface of molten metal, and the adsorbed oxygen molecules will be decomposed into oxygen atoms at high temperature, and the oxygen atoms will get electrons and become ions, and then combine with metal ions to form metal oxides. The whole oxidation process can be completed in an instant when the surface of molten metal is exposed to air. When a monolayer monomolecular oxide film is formed, the further oxidation reaction needs to be carried out through the oxide film in the form of electron movement or ion transfer, and the oxidation rate of static molten solder gradually decreases. Molten SnCu0.7 oxidizes faster than Snpb37 alloy.
Pilling-Bedworth) <1÷1÷ theory shows that whether the metal oxide film is dense or not is the key to oxidation resistance, and whether the oxide film is dense or not mainly depends on whether the volume of oxide after metal oxidation is larger than that before metal oxidation; The surface of molten metal is covered with a dense and continuous oxide film, which prevents oxygen atoms from diffusing inward or metal ions from diffusing outward, thus slowing down the oxidation rate. The composition and structure of oxide film are different, and its growth speed and mode are also different. After the molten SnCu0.7 and Snpb37 alloys are cooled and solidified at 260℃ under the same conditions, the surface of SnCu0.7 is rough, while the surface of Snpb37 is fine. From this point of view, the density integrity of the oxide film of liquid SnCu0.7 alloy is worse than that of Snpb37.
Alexei grigoriev of Harvard University < 2 > and others put a tin sample with a purity of 99.9999% into a crucible, heated it to 240℃ under ultra-low vacuum, and then filled it with pure oxygen. The oxidation process of molten tin was observed by X-ray diffraction, reflection and scattering. In their research, they found that molten tin had oxidation resistance before reaching the oxidation pressure. When the pressure reaches the range of 4× 10-4pa to 8.3× 10-4pa, oxidation begins. Under this oxygen partial pressure limit, the growth of oxide "islands" on the surface of molten tin was observed. The surface of these islands is very rough, and the X-ray specular reflection signal on the clean surface of tin is uniformly weakened, which can prove the existence of oxide fragments. The X-ray diffraction pattern of surface oxide is not matched with any known tin oxide, only two Bragg peaks appear, and the scattering phasor is √3/2, and the face-centered cubic structure with clear intensity is observed. The surface structure of molten liquid tin was measured by tangential incidence scanning (GID) and compared with the known tin oxide. It can be said that at this temperature and pressure, the oxide phase structure of molten liquid tin in pure oxygen is different from that of SnO or SnO2.
In addition, the standard free energy of formation of SnO2 is different from PbO at different temperatures. The former has a low free energy of formation and is easier to generate, which explains why the oxide slag increases greatly after lead-free. Table 1 lists the Gibbs free energy of oxide formation, and it can be seen that SnO2 is easier to form than other oxides. Usually, the oxide film of static melting solder is a mixture of SnO2 and SnO.
According to the distribution law, oxides can be partially dissolved in molten liquid solder, and at the same time, due to the solubility difference, metal oxides diffuse inward, and the oxygen content in internal metals gradually increases, which can explain to some extent why alloy metals extracted (or reduced) at high temperature are easier to oxidize and have more oxide slag. With the different composition and structure of oxide film, the growth rate, growth mode and distribution coefficient of oxide in solder melt will be very different, which is closely related to the composition of solder. In addition, oxidation is also related to temperature, partial pressure of oxygen in gas phase, absorption and decomposition speed of oxygen on the surface of molten solder, bonding ability between surface atoms and oxygen atoms, density of surface oxide film, dissolution and diffusion ability of products, etc.
Table 1 Standard Gibbs Free Energy of Oxide
oxide
△G0f。 T (oxygen atom)/(kilojoule/gram)
298K
400 thousand
500 thousand
600 thousand
Decline politely.
- 188.8
- 178.8
- 168.7
- 159.5
stannic dioxide
-260. 1
-249.7
-239.7
-228.8
copper oxide
- 129.4
- 1 19.7
- 1 1 1.0
10 1.7
Ag2O
- 10.5
-3.8
2.5
8.8
2 >, dynamic melting solder oxidation
Shuangfeng is widely used in wave soldering process. The first peak is the trickle peak, whose wave width is relatively narrow and the flow rate of molten solder is relatively fast. The second wave peak is laminar wave, the wave surface is flat and stable, such as mirror surface, and the flow velocity is slow. On the surface of the wave, the newly melted solder is constantly in contact with oxygen. Oxidation slag is formed when molten solder flows rapidly, which is very different from static oxidation. There are three forms of dynamically formed welding slag:
A. The molten solder in a tin furnace with an oxide film on its surface is oxidized at high temperature through the mutual contact between its surface exposed to air and oxygen. This oxide film is mainly formed on the relatively static surface of molten solder in tin furnace, and its main component is SnO. As long as it does not damage the surface of the molten solder, it can isolate the air and protect the molten solder inside from further oxidation. This surface oxide film usually accounts for about 10% of the oxidation residue.
B, black powder The particles of this powder are very large, which are generated at the junction of the molten solder surface and the shaft of the mechanical pump, and are distributed around the shaft in a circular shape and piled up together. The high-speed rotation of the shaft will rub against the molten solder, but because of the good thermal conductivity of the molten solder, the temperature of the molten solder around the shaft is not higher than other areas. The formation of black powder is not caused by the increase of friction temperature, but the vortex formed by the surface of molten solder around the rotation of the shaft. With the movement of the shaft, the oxide is spheroidized due to friction. At the same time, friction can increase the surface energy of solder particles and aggravate oxidation; Accounting for about 20% of the oxidized slag.
C. In the wave crest generator of the oxide slag mechanical pump, there is a violent mechanical stirring action, which forms a violent vortex movement in the solder bath. Due to unreasonable design, the surface of the solder bath rolls violently. These eddies and tumbling movements form the phenomenon of oxygen absorption, and the oxygen in the air is continuously sucked into the molten solder. Due to the limited oxygen absorption, the oxidation process inside the molten solder can not be carried out as fully as the liquid level, so a large number of silvery sandy (or tofu-like) oxide slag is produced inside the molten solder. This kind of slag forms a lot, oxidizes in the molten solder, and then floats to the liquid surface to accumulate in large quantities, even occupying most of the space of the solder bath, blocking the pump cavity and flow channel, eventually leading to the continuous decline of the peak height and even damaging the pump blades and shafts; The other is that the contact area between the molten solder and oxygen in the air increases during the reflow of the molten solder to the solder tank, and at the same time, a violent eddy current motion is formed in the molten solder tank, forming oxygen absorption phenomenon, thus forming a large number of oxide slag. These two kinds of slag usually account for 70% of the total oxide slag, which is the biggest waste. The application of lead-free solder will produce more oxide slag, and SnCu is more than SnAgCu. The typical structure is 90% metal plus 10% oxide.
Japanese scholar Tadashi Takemoto < 3 > and others tested three kinds of solders, SnAg3.5, SnAg3.0Cu0.5 and Sn63Pb37, and found that the weight of oxide slag of all solders increased linearly, and the growth rate of oxide slag of the three solders was almost the same, that is, the growth rate had little to do with the composition of the solders. The formation of oxide slag is related to the fluid flow of molten solder. The instability of fluid and waterfall effect may cause the absorption of oxygen and the tumbling of molten solder, which makes the formation process of oxide slag more complicated. In addition, from the process point of view, the factors affecting the formation of oxide slag include peak height, welding temperature, welding atmosphere, peak disturbance, type or purity of alloy, type of flux used, PCBA content passing through the peak and quality of original solder.
Fourth, the structure of tin oxide slag
Generally speaking, tin slag is mainly composed of tin oxide SnO2 (namely tin ash), tin Sn wrapped in tin oxide and a small amount of carbonized substances, and the proportion of tin Sn wrapped in tin oxide is at least over 50%, and some even as high as 90% (the specific content depends on the situation of slag fishing).
Tin oxide (tin ash) in tin slag is usually SnO2, gray powder, square, hexagonal or orthogonal crystal; The density is 6.95g/cm3; Melting point1630℃; Structural formula: o: SnO; Molecular weight:150.69; Sublimate at 1800 ~ 1900℃; Insoluble in water, alcohol, dilute acid and lye; Slowly dissolving in hot concentrated alkali solution and decomposing, and fusing with alkali to generate stannate; Dissolved in concentrated sulfuric acid or concentrated hydrochloric acid; Tin content: more than 70%-90%.
Verb (abbreviation of verb) Measures to reduce oxidation slag
Scholars and enterprises at home and abroad have done a lot of research on the measures to reduce the oxide slag of lead-free wave soldering, mainly in the following aspects:
1 & gt； And is protected by nitrogen.
Nitrogen protection is an effective measure to reduce the generation of oxide slag, and separating air from molten solder with nitrogen can effectively reduce the generation of oxide slag. Because the wettability of lead-free solder is obviously weaker than that of traditional lead solder, and it is easy to oxidize, lead-free welding under nitrogen protection has become one of the commonly used technologies.
When welding in nitrogen atmosphere, the oxidation degree of lead-free solder decreases obviously with the decrease of oxygen solubility. When the oxygen solubility under nitrogen protection is lower than 50ppm or less, the lead-free solder will not be oxidized basically, and better welding quality can be obtained. When the oxygen solubility is 50-500ppm, the amount of oxidation slag can be reduced by about 85%-95%.
Linde launches SOLDERFLEX? In the inert gas protection system of LIS wave furnace, the wave soldering equipment was reformed, that is, the stainless steel structure with wave soldering groove was extended into the solder pool, and a plurality of gas injection pipes and gas control operation panels were configured, so that inert gas directly acted on most places where oxide slag was generated to control the generation of oxide slag. It is said that the oxygen content in the welding zone can be controlled at about 100PPM, and the oxide slag can be reduced by 50%-80%.
According to the data provided by Claude cars AC 4 and others, there is almost no difference in the relative content of oxide slag reduction for different alloy types. Table 2 shows the research results of foreign scholars.
Table 2 Comparison of oxide slag formation of lead-free solder under atmospheric conditions and nitrogen protection conditions < 5 >
Alloy type
Oxide slag formation (g/h)
Under atmospheric conditions
Under the protection of nitrogen
ITRI laboratory
Commercial wave soldering equipment
ITRI laboratory
Commercial wave soldering equipment
SnCu0.7
28.7
908
1.68
45
SnAg3.5
22.8
72 1
1.2 1
36
SnAg2Cu0.8Sb0.5
19.8
626
0.98
3 1
SnIn20Ag2.8
Eight hundred
40
Nitrogen protection will also bring disadvantages, mainly increasing the production and operation cost of solder beads on the surface of PCBA, and the usually saved solder is not enough to offset the operation and maintenance cost of purchasing liquid nitrogen or nitrogen generator. However, from the quality of solder and the use of expensive lead-free solder, whether it is economical or not is another matter. In a word, before using nitrogen protection system, it should be carefully calculated and considered.
2 > Research and Application of Electromagnetic Pump
If the wave crest generator of the mechanical pump is not designed properly, there will be strong mechanical stirring, which will form strong vortex motion and liquid surface tumbling in the solder tank, forming oxygen absorption phenomenon, and oxygen in the air will be continuously sucked into the molten solder, forming a large number of oxide slag, and then floating on the liquid surface to accumulate continuously. 1969, Swiss scholar R.F.J.PERRIN first put forward a new scheme of pumping molten metal solder by electromagnetic pump. In the mid-1970s, KRISTN Company of Switzerland used this technology to launch a series of single-phase AC conducted electromagnetic wave peak welding machines (6TF series) for the first time in the industry. 1982, France also obtained a patent for similar technology. In the late 1980s, the 20th Research Institute of China Ministry of Electronic Industry invented a single-phase induction electromagnetic pump for molten metal, and made a prototype. The development of power technology has opened up a new way to produce melting solder peaks in microwave peak welding equipment. He removed all the rotating parts of the mechanical pump (including the motor). Different from the conductive electromagnetic pump invented by Swiss scholars, it completely removed the conductive current and its generation system, and made great progress in technology.
At present, there are two kinds of electromagnetic pumps: single-phase induction and multi-phase induction. The advantages of electromagnetic pump are:
A, never wear, long life and convenient maintenance.
B, the wave crest is stable, which reduces the oxidation of molten solder and can automatically cancel the grid voltage.
C, comprehensive utilization of energy and high efficiency.
D, the dynamic characteristics of solder wave crest are good.
E, wave soldering flux temperature drop is small.
Disadvantages: there are also fluid instability and waterfall effect, and the tin slag formed by these phenomena cannot be reduced. At present, electromagnetic pumps are more expensive, far less widely used than mechanical pumps.
Study on 3 \u Tin Slag Separation Device
That is, the tin slag reduction machine in the industry, Cookson Company has developed a device for automatically removing oxide slag. He specially designed a nozzle to guide the flowing molten solder to the designated position, and automatically skimmed the oxide slag to the collection device with a skimmer. Below the collecting device is a hot roller for collecting and compressing oxidation slag. Solder that can be obtained separately is collected, sorted and guided to flow into a high-temperature furnace, and finally formed for reuse. The unusable waste residue Sno2 (namely tin ash) is accumulated in the container for cleaning and recycling. It is said that the efficiency of slag cleaning is 80% higher than that of manual cleaning.
Japanese scholar Tadashi Takemoto < 3 > and others used a self-developed tin slag separation and reuse device in the experiment, which was attached to the tin furnace. The wave soldering machine can work for 8 hours, while the tin slag separation system (OSS) can work for half an hour. It is said that this system can reduce oxidation slag by half.
Japan Qianju Company has introduced a solder recycling equipment, the principle of which is to put oxide residues into the equipment, add specially treated sesame seeds after heating, and mix and stir with the oxide residues. Sesame oil will reduce the oxides in the oxide residue mixture and adsorb them all on sesame seeds, thus realizing the separation of solder and oxide.
In addition, Japanese and Hong Kong manufacturers have introduced separators to separate tin slag by mechanical stirring, and a domestic manufacturer has introduced a tin slag reduction machine that relies on chemical action. It is said that the reduction rate can reach about 80%.
The equipment belongs to off-line separation processing. Due to the physical separation method, the tin oxide slag SnO2 cannot be reduced to tin Sn. We see the so-called reduced tin, but it is pure tin mixed with tin slag in real time. The high temperature, pressure and friction of the reducing agent in the working state will make the tin slag reoxidize the pure tin mixed in it when it is compacted. According to the distribution law, oxides can be partially dissolved in molten liquid solder. At the same time, due to the solubility difference, the metal oxide diffuses inward, and the oxygen content in the internal metal gradually increases, which makes the solder quality worse. Most solder manufacturers use phosphorus to improve their oxidation resistance. The antioxidant elements in the alloy solder precipitated (or reduced) at high temperature have been consumed, so the solder treated by this method is very easy to oxidize and has more oxide slag. It takes up space, needs special personnel to operate, consumes electricity and makes noise, and the processes of salvage, transportation, storage and repair are complicated, which increases the management cost. In the case that the reduction rate itself is not high, it is better to directly exchange tin bars with manufacturers, and subtract the rent of equipment occupation space+storage space rent+employee salary+electricity fee+equipment input. Because it is easy to cause secondary pollution and consume electric energy, the feasibility of using this kind of equipment will also be questioned when the power supply itself is very tight!
All the above methods are based on the principle of physical separation to separate pure tin and Sn mixed in oxide slag. Although the production of oxide slag can be reduced to a certain extent, the oxidized SnO2 can not be reduced to tin Sn by this method at all, and the tin precipitated by high temperature heating is easier to be oxidized and produce more tin oxide slag. After removing the related costs, the purpose of saving costs can not be achieved at all! Therefore, most electronic manufacturing enterprises are looking for a chemical product that can not only resist oxidation but also reduce SnO2 to Sn.
4 > Use of anti-oxidation solder
Japanese scholar Tadashi Takemoto [3] and others added P and Ge elements to solder for research. The alloy solders used in the experiment are SnAg and SnAgCu, and the specific chemical composition is shown in table 3. The equipment is a small wave crest tin furnace with a capacity of 15KG and a test temperature of 250℃. The experimental results show that the weight of oxidation slag increases linearly with time. Adding a small amount of Ge and P can effectively reduce the weight of oxide slag, and adding P can reduce the weight of oxide slag to about 50%. The chemical analysis of oxidation slag shows that among the trace elements contained in oxidation slag, the addition of Ge is 2-9%, and the phosphorus is more than 4.5 times. The main component of oxide slag is SnO, the oxygen content is about 5at%, and 90% of oxide slag is composed of metal.
Table 3 Chemical Composition of Various Solder Alloys
raw material
Simplified Chinese characters
Element mass percentage (%)
(Reacting to what others say or expressing anger or annoyance) Hmm.
copper
P
germanium (Ge)
other
tin
SnAg3.5
Salvation Army (Salvation Army)
3.56
Balance (same as balancing)
SnAg3.5P0.003
SA30P
3.48
0.00325
Balance (same as balancing)
SnAg3.5P0.006
SA60P
3.50
0.006
Balance (same as balancing)
SnAg3.5P0.0 1
SA 100P
3.48
0.0092
Balance (same as balancing)
SnAg3.5Ge0.05
SA5Ge
3.50
0.050
Balance (same as balancing)
SnAg3.5Ge0. 1
SA 10Ge
3.5 1
0.090
Balance (same as balancing)
SnAg3.5Cu0.7
SA7C
3.48
0.7 1
Balance (same as balancing)
SnAg3.0Cu0.5
SA5C
3.04
0.53
Balance (same as balancing)
SnAg3.0Cu0.5P0.004
SA5C40P
3.03
0.5
0.004
Balance (same as balancing)
SnAg3.5Cu0.7Ge0.05
SA7C5G
3.5 1
0.67
0.049
Balance (same as balancing)
SnAg3.5Cu3.50.7Ge0. 1
SA7C 10G
3.5
0.68
0. 1
Balance (same as balancing)
SnCu0.5Ag0.3
Cardiac arrest
0.34
0.49
Balance (same as balancing)
SnCu0.5Ag0.3P0.004
SCA40P
0.34
0.49
0.004
Balance (same as balancing)
Domestic scholars have also proposed to add various trace elements such as TI, Ga, Re, Sb, In and Ni. To lead-free solder with different alloys to reduce the generation of oxide slag, have achieved certain results. At present, the lead-free solders used in domestic wave soldering industry are mainly SnCu and SnAgCu. Most solder manufacturers use P element to improve the oxidation resistance, but with the extension of time and the consumption of trace elements, the oxidation resistance will gradually fail. So there is the emergence of antioxidant reductant!
Research and application of tin slag reducer (powder)
The generation of oxide slag is closely related to the flow behavior of molten solder. The more unstable the fluid is, the more disturbed it is, and the easier it is to absorb oxygen, resulting in a large increase in oxide slag. Up to now, the formation mechanism of solder oxide slag mixture in wave soldering process is not clear enough. For electronic production enterprises that use wave soldering, it is best to choose wave soldering equipment with reasonable injection system design, less oxide slag and convenient salvage of oxide slag, and then cooperate with antioxidant reductant with high cost performance to reduce oxide slag finally.
Because the antioxidant trace elements in lead-free solder tend to condense on the surface of molten solder before Sn, and combine with oxygen in the air, the trace elements are rapidly consumed and the solder loses its antioxidant effect. Fluid instability and waterfall effect, as well as oxygen absorption caused by molten solder tumbling; According to the distribution law, oxides can be partially dissolved in molten liquid solder, and at the same time, due to the solubility difference, metal oxides diffuse inward, and the oxygen content in solder alloy increases gradually for various reasons. Therefore, adding antioxidant reductant into the solder melting furnace is the most practical and effective measure, which can reduce the generated tin oxide slag immediately without accumulation, and at the same time effectively prevent the further generation of oxide slag. Therefore, domestic and foreign merchants have successively introduced tin slag (tin oxide slag, also known as tin slag in SnO2 industry) as antioxidant reductant (powder).
Necessary conditions for antioxidant reductant:
A>, must meet the requirements of environmental protection, without affecting the working environment of the production site and the alloy composition of the solder;
The residue after b> reaction is not sticky or can't fly away, which will not pollute the surface of PCBA and existing production equipment (such as wave soldering, etc.). );
C> is non-flammable, non-corrosive, does not change the existing production process, and does not affect the daily maintenance of existing equipment;
The dosage of d> is small, the reduction rate is high, and the residue after reaction is easy to handle, and it is best to be biodegradable. Really save energy and reduce consumption for enterprises from the perspective of environmental protection.
A company in Taiwan Province Province has developed a kind of tin slag reducing powder, which mainly absorbs various impurities and oxides to avoid oxidation and heat loss of molten solder. It is said that the use of reducing powder can reduce solder oxidation by about 95%. Disadvantages are heavy smoke and pungent smell. When using this reduced powder, the wave soldering equipment must be improved, and the residue after reaction is sticky and turns into hard solid after cooling, which brings some inconvenience to the daily maintenance of the equipment.
The molten solder surfactant developed by American P.Kay Metal Fein-Line Partnership Company has two functions when it comes into contact with molten solder: one is to form a protective film on the surface of molten solder to protect the solder from oxidation, and the other is to make the active component react with metal oxide, dissolve in the active agent, and suspend between metal oxide particles and residual active agent as an organometallic compound. The active agent does not react with metal until the agent is consumed, and only reacts with oxide residue, which is smokeless and tasteless. When the metal oxide in the oxide slag is dissolved, the arrangement of the interconnected oxides is open, and any metal trapped in the oxide slag gathers and flows back to the molten solder. And its components are not influenced by the components of the active agent. It is said that this technology can reduce the cost of solder by 40%-75%; The disadvantage is that the wave soldering equipment must be improved when using this reducing agent. After the reaction, the residue is sticky and turns into a hard solid after cooling. It is difficult to clean the equipment or PCBA and may even block the nozzle, which brings some inconvenience to the daily maintenance of the equipment. Once you accidentally touch the PCB, it will be difficult to clean it, which will affect the electrical performance of the product and the reliability of solder joints! And the reduced solder cost is equal to the cost of using the active agent.
Shicun-JR07 tin slag antioxidant reductant developed by Shenzhen Qiqi Xinhua Technology Co., Ltd. is a polymer organic compound, which is compounded by various surfactants, wetting agents and dispersants through scientific methods. Does not contain any heavy metals, and is soluble in most organic solvents and water; The PH value is neutral between 6 and 7; Excellent high temperature resistance (ignition point above 330℃) and volatility resistance (almost non-volatile), almost smokeless, tasteless, non-sticky, non-corrosive, and has anti-oxidation and reduction functions; The dosage is small, and the reduction efficiency is high, reaching more than 90%; According to Flextronics' evaluation report, after deducting the use cost of Shicun-JR07 tin slag antioxidant reductant, the amount of solder can be saved by 38%. Evaluation reports of Foxconn, Shenzhou, Xudian, PRIMAX, GBM, HUNTKEY, etc. All of them gave a high evaluation of Shicun-JR07 tin slag antioxidant reducing agent. The product is easy to operate, and can be directly added into the tin bath to reduce tin slag, thus directly reducing the amount and times of tin slag fishing. Improve the production efficiency and the utilization rate of solder; Will not change the effective composition of solder; Do not pollute PCBA；; ; High reduction efficiency; Excellent high temperature resistance and volatility, residue is non-sticky, fragile, easily soluble in water, biodegradable, will not sink to the bottom of the cylinder, do not worry about blocking the nozzle or impeller, which is conducive to equipment maintenance. Daily maintenance of the equipment can only be wiped with a wet rag.
ICHIMURA-JR07 tin slag antioxidant reductant can separate tin wrapped in oxide slag, and can also reduce tin oxide (SnO2) to usable tin (Sn). Moreover, the effective components in the antioxidant reductant combine with the oxygen element O2 in the air before Sn, which obviously reduces the oxygen O2 content in the solder melt, prevents the solder melt from further oxidation, enhances the fluidity of the surface of the solder melt, and effectively helps the welding of PCBA.
The products have completely passed SGS, SIR, MSDS, STIR, slicing and other tests or certifications.
The process of oxide reduction can be roughly regarded as: O2+R = OXRX；; PbOx+R = p b+ OR( 1)； SnOy+R = Sn +OR (2), where: PbOx is lead oxide, R is liquid reductant, Pb is reduced lead, OR is oxide, SnOy is tin oxide, and Sn is reduced tin. In the process of regeneration of antioxidant reducing agent for ICHIMURA-JR07 tin slag, the liquid covering chemical displacement reaction reduction method was successfully adopted. This reducing agent is a non-toxic organic material, biodegradable, and its own and oxides are harmless to human beings and the environment. On the one hand, the temperature is controlled in a relatively low range below 280℃, far below the temperature of lead smoke above 400℃ (the temperature of tin slag reducer); On the other hand, the surface coverage of liquid reductant also effectively inhibits the escape of lead smoke; The water solubility of the product determines that it contains a small amount of water, and the small amount of smoke seen during use is actually water vapor; This not only effectively reduces the lead and tin oxide in welding slag, but also effectively avoids the pollution of residue and lead smoke to the environment.
The advantages of Shicun-JR07 tin slag antioxidant reductant are as follows:
A & gtPH 6-7 is neutral, non-flammable, non-corrosive and non-sticky;
, ; B> is almost smokeless, tasteless, halogen-free, does not contain any heavy metal components, and conforms to DOES.
The consumption of c> is small, and the reduction rate is high, reaching more than 90%, which effectively improves the product quality and the utilization rate of solder;
D> will not change the effective composition of solder; Do not pollute PCBA, and do not worry about blocking the nozzle or impeller;
E> reduces the oxygen content in molten solder, enhances the fluidity and wettability of solder, and effectively helps PCBA welding;
F> can operate online without changing equipment and increasing personnel, and directly add tin bath to reduce the amount and times of tin slag fishing.
The residue after g> reaction is muddy, non-sticky, fragile and easily soluble in water, which is beneficial to the daily maintenance of equipment;
The residue after h> reaction can be hydrolyzed or biodegraded; Really save energy and reduce consumption for enterprises from the perspective of environmental protection.
My> products have passed SGS, MSDS, SIR, STIR, slicing and other testing certifications. , truly belongs to environmental protection and energy-saving products.
How to distinguish tin slag;
This question is really difficult to answer. I am a tin smith. To learn to distinguish the smell of tin slag, I have to observe it regularly. But I can make a preliminary statement: grab a handful of tin slag and put it in a spoon, then heat it on the stove, and stir it constantly with objects or chopsticks with high melting point until the tin in the tin slag melts. After cooling, slowly pour the tin water on the ground to see the surface. You can also pour it for a long time, so it looks like a strip. After cooling, the tin bar can be folded repeatedly by hand, and the tin-lead alloy above 50 degrees will make a "rustling" sound, but the specific degree is unclear in a few words.
Recovery and identification of tin slag: generally, gray has high tin content, the color with high lead content is dark, the color with high tin content is slightly yellow, and there is a click when bending hard. ...