Abstract: Due to the influence of environmental protection packaging, the electronics industry is facing the challenge of turning to new materials and new process methods, and they are required to have the same reliability, manufacturability, price, and practicality. Pure tin or tinplate products will be the ultimate choice.
As people are increasingly aware of the impact of various industrial materials on the environment and health, the way materials are processed and used has also undergone great changes. In the electronics industry, the elimination of lead in surface treatment and the use of brominated and lanthanum-containing materials as flame retardants in casting mixtures has become the subject of current research and discussion since they are harmful to human health and the environment. .
The purpose of this article is to determine if the composition of pure tin and tin-copper as the final product is appropriate, and the reliability of the casting mixture without the bromine and antimony components. In addition, packaging products with these new materials were also evaluated to verify the effect of the higher reflux point temperature (260°C). The ultimate goal is to obtain environmentally friendly packaging products, and whether these packaging products will maintain equal or even better moisture sensitivity when the reflow temperature rises from 245°C to 260°C.
For component manufacturers, the use of tin-lead components instead of raw lead treatment should be easily controlled during the electroplating process, and they should have the same solderability, surface properties, and mechanical properties. Tin and tin-copper plating products (both of which are rough finished products) are suitable substitutes for tin-lead.
Although pure tin products have been widely used in ceramic products and other similar products, they cannot be used in fine resin equipment because the deposition phenomenon will continue to occur in the equipment over time to generate whiskers.
Recently, some electroplating chemical companies have made the latest technological breakthroughs regarding the whisker phenomenon. They have developed a pure tin deposit with a conical/polygonal structure, and the large particle size can suppress the production of such whiskers. Compared to tin-silver or tin-bismuth plating or lead-frame pre-plated palladium, pure tin has better practicality and lower price, and its application is more than other alloys used in lead-free processing. Easy to understand. Tin-copper products solve the problem of whiskers by adding trace amounts of copper (less than one percent) to pure tin products, which are abundant and less expensive than tin-silver, tin-bismuth and palladium. However, the presence of these two alloy compositions requires an increase in the temperature of the reflow process. Because the lead-free alloy has a higher melting point: pure tin is 232°C and tin-copper is 227°C. The most important factor in the increase in reflow temperature is the use of high-temperature solder materials such as tin-silver-copper.
Casting is another area where packaging processes are transformed into harmless materials. The compounds used must pass the UL Standard UL94-Vo test and require flame retarding ingredients. Halides and antimony oxides are often used for this purpose. However, these materials may produce highly toxic dioxins and furans when burned. Studies by mold compound manufacturers have shown that halogen-free, non-fluorene substitutes are primarily hydroxylated, with aluminum hydroxide and magnesium hydroxide being the most likely, or transition metal magnesium hydroxide (TMMHC). These components were selected as retardants after testing for mold properties through flammability, TGA characteristics, warpage and shrinkage, glass transition temperature (Tg), viscosity, and reliability.
The method assessment process is mainly performed by the following procedure:
Preparation of metal blocks and lead blocks ready for testing Ready for operation with unprocessed mixture Mold post-cure Pure lead or tin-copper for lead-free plating Marking trimming and forming Tendrils testing
The chemicals and conditions used in the pretreatment (evacuation and etching) and post-treatment (neutralization) of the plating process are the same as those in the tin-lead plating process. The test uses a pure tin metal ball as the anode. Representative packaging products MQFP28×28, MQFP14×20, LQFP14×14 and PLCC68L are used as testing tools. Test different packaging materials at higher reflow temperatures and compare their sensitivity to humidity. These packaging materials represent different packaging series, sizes, and thicknesses. Biphenyl compounds (such as LQFP) have better reliability and therefore are used as thinner packages, while OCN compounds (such as MQFP and PLCC) are used as larger packages.
During the pretreatment phase of the humidity sensitivity test, the peak reflow temperature was 245°C. The biggest difference in lead-free applications is that the reflow temperature is higher than 260°C. Scan before and after exposure to check if the packaging material can withstand higher heat applications.
Results and Discussion 1. Plating Quality: Tin-lead plating quality was typically tested on tin and tin-copper samples to determine the suitability of these alternative materials. It has been found that pure tin electroplating products have good similarities with tin-lead products in terms of thickness, surface/mechanical quality (including examination of tentacles), and solderability. The weldability was tested to Mil-Std-883D (steam aging time is 8 hours, resin-based welding processing time is 5 to 10 seconds, tin-lead welding processing time is 5±0.5 seconds), but the aging conditions are more stringent: It was baked at 155°C for 48 hours and evaporated for 16 hours. The ionic contaminant levels were also measured with ion traps. The test results were all below the maximum allowable value of 2 μg/in2 and the measured maximum was only 0.0023 μg/in2. Through the thermal conductivity trace analysis, the carbon content in the sediment is also very low, less than 0.01% (the specified limit is 0.05%). Through the same test, tin-copper plating and tin-lead plating have the same quality and solderability. The maximum level of ionic contaminants in Sn-Cu plating is 0.0022μg/in2, and the carbon content is less than 0.01%. Tin, lead, pure tin, and tin and copper have slightly different surface plating properties.
2. SEM/EDX analysis: Pure tin samples can be plated not only at the general density of high-speed applications, but also at high densities to check for differences in deposition patterns. We hope that the larger the density is, the rougher the surface will be, but we found that the surface pattern did not change and no burning occurred. Pure tin plating is generally stored at 50° C. for 18 months, and no whisker growth was observed under 30× magnification. This condition is true in both the unpressurized (straight) and stressed (curved) parts of the lead material.
The SEM (middle layer image) and cross-sectional analysis of the electroplated tin-copper were found to be similar to that of tin-lead. The cross-sectional analysis of tin is along the length direction and can distinguish between the bend and the straight part; and the tin-copper cross-sectional analysis is along the width direction.
3, electroplating processability: The actual investigation and evaluation of the high-speed electroplating production line found that the pure tin process is easier to control than tin-lead and tin-copper alloy systems. Compared with the tin-lead system, the pure tin system only needs to control three factors, and because it is a single metal, there is no problem that the alloy mixture is difficult to control. The content of tin and nucleic acid can be easily determined by titration, and the concentration of the additive can also be determined by UV-visible spectrometry. It is also certain that this special pure tin composition is suitable for high-speed electroplating processes, so it will not be necessary to spend extra money on tin-lead plating in the future.
Titration and UV-visible spectrometry can also be used for the chemical control of tin-copper processing. However, alloy mixtures are difficult to control. The content of copper in the electroplating layer must be less than one percent. At present, there is no suitable method to measure the composition. The coating containing tin, lead, and tin can often be measured by an X-ray fluorescence emitter (XRF). This method is not suitable for the tin-copper mixture because it is difficult to detect the copper content of the tin-copper coating on the surface of the copper product because both the plating layer and the main frame contain copper. Therefore, the basic material will have an impact on the measurement results. Merchants recommend a destructive test that dissolves all of the sediment and analyzes the composition by microparticle absorption spectrometry.
4. Humidity Sensitivity: Some conclusions have been drawn by testing packaging products. The current focus is on whether the packaging material itself can maintain a certain degree of integrity after 3X pretreatment at a reflow temperature of 260[deg.] C. (eg no delamination between the mixture and the plating layer). Unprocessed biphenyl compounds in LQFP packages can withstand 3 levels of pretreatment. The raw OCN component in MQFP/PLCC can only withstand 4 levels of pretreatment.
in conclusion
The test results clearly show that pure tin is a reasonable solution for lead-free packaging challenges. It can be stored for 672 hours at 85°C/85% relative humidity or 6 to 18 months at 50°C/85% relative humidity with no whisker growth. The reliability of temperature cycles, pressure tolerance, humidity, and high temperature storage is still being further measured. Further research is needed on how to achieve lower reflow temperatures and broader reliability.
As people are increasingly aware of the impact of various industrial materials on the environment and health, the way materials are processed and used has also undergone great changes. In the electronics industry, the elimination of lead in surface treatment and the use of brominated and lanthanum-containing materials as flame retardants in casting mixtures has become the subject of current research and discussion since they are harmful to human health and the environment. .
The purpose of this article is to determine if the composition of pure tin and tin-copper as the final product is appropriate, and the reliability of the casting mixture without the bromine and antimony components. In addition, packaging products with these new materials were also evaluated to verify the effect of the higher reflux point temperature (260°C). The ultimate goal is to obtain environmentally friendly packaging products, and whether these packaging products will maintain equal or even better moisture sensitivity when the reflow temperature rises from 245°C to 260°C.
For component manufacturers, the use of tin-lead components instead of raw lead treatment should be easily controlled during the electroplating process, and they should have the same solderability, surface properties, and mechanical properties. Tin and tin-copper plating products (both of which are rough finished products) are suitable substitutes for tin-lead.
Although pure tin products have been widely used in ceramic products and other similar products, they cannot be used in fine resin equipment because the deposition phenomenon will continue to occur in the equipment over time to generate whiskers.
Recently, some electroplating chemical companies have made the latest technological breakthroughs regarding the whisker phenomenon. They have developed a pure tin deposit with a conical/polygonal structure, and the large particle size can suppress the production of such whiskers. Compared to tin-silver or tin-bismuth plating or lead-frame pre-plated palladium, pure tin has better practicality and lower price, and its application is more than other alloys used in lead-free processing. Easy to understand. Tin-copper products solve the problem of whiskers by adding trace amounts of copper (less than one percent) to pure tin products, which are abundant and less expensive than tin-silver, tin-bismuth and palladium. However, the presence of these two alloy compositions requires an increase in the temperature of the reflow process. Because the lead-free alloy has a higher melting point: pure tin is 232°C and tin-copper is 227°C. The most important factor in the increase in reflow temperature is the use of high-temperature solder materials such as tin-silver-copper.
Casting is another area where packaging processes are transformed into harmless materials. The compounds used must pass the UL Standard UL94-Vo test and require flame retarding ingredients. Halides and antimony oxides are often used for this purpose. However, these materials may produce highly toxic dioxins and furans when burned. Studies by mold compound manufacturers have shown that halogen-free, non-fluorene substitutes are primarily hydroxylated, with aluminum hydroxide and magnesium hydroxide being the most likely, or transition metal magnesium hydroxide (TMMHC). These components were selected as retardants after testing for mold properties through flammability, TGA characteristics, warpage and shrinkage, glass transition temperature (Tg), viscosity, and reliability.
The method assessment process is mainly performed by the following procedure:
Preparation of metal blocks and lead blocks ready for testing Ready for operation with unprocessed mixture Mold post-cure Pure lead or tin-copper for lead-free plating Marking trimming and forming Tendrils testing
The chemicals and conditions used in the pretreatment (evacuation and etching) and post-treatment (neutralization) of the plating process are the same as those in the tin-lead plating process. The test uses a pure tin metal ball as the anode. Representative packaging products MQFP28×28, MQFP14×20, LQFP14×14 and PLCC68L are used as testing tools. Test different packaging materials at higher reflow temperatures and compare their sensitivity to humidity. These packaging materials represent different packaging series, sizes, and thicknesses. Biphenyl compounds (such as LQFP) have better reliability and therefore are used as thinner packages, while OCN compounds (such as MQFP and PLCC) are used as larger packages.
During the pretreatment phase of the humidity sensitivity test, the peak reflow temperature was 245°C. The biggest difference in lead-free applications is that the reflow temperature is higher than 260°C. Scan before and after exposure to check if the packaging material can withstand higher heat applications.
Results and Discussion 1. Plating Quality: Tin-lead plating quality was typically tested on tin and tin-copper samples to determine the suitability of these alternative materials. It has been found that pure tin electroplating products have good similarities with tin-lead products in terms of thickness, surface/mechanical quality (including examination of tentacles), and solderability. The weldability was tested to Mil-Std-883D (steam aging time is 8 hours, resin-based welding processing time is 5 to 10 seconds, tin-lead welding processing time is 5±0.5 seconds), but the aging conditions are more stringent: It was baked at 155°C for 48 hours and evaporated for 16 hours. The ionic contaminant levels were also measured with ion traps. The test results were all below the maximum allowable value of 2 μg/in2 and the measured maximum was only 0.0023 μg/in2. Through the thermal conductivity trace analysis, the carbon content in the sediment is also very low, less than 0.01% (the specified limit is 0.05%). Through the same test, tin-copper plating and tin-lead plating have the same quality and solderability. The maximum level of ionic contaminants in Sn-Cu plating is 0.0022μg/in2, and the carbon content is less than 0.01%. Tin, lead, pure tin, and tin and copper have slightly different surface plating properties.
2. SEM/EDX analysis: Pure tin samples can be plated not only at the general density of high-speed applications, but also at high densities to check for differences in deposition patterns. We hope that the larger the density is, the rougher the surface will be, but we found that the surface pattern did not change and no burning occurred. Pure tin plating is generally stored at 50° C. for 18 months, and no whisker growth was observed under 30× magnification. This condition is true in both the unpressurized (straight) and stressed (curved) parts of the lead material.
The SEM (middle layer image) and cross-sectional analysis of the electroplated tin-copper were found to be similar to that of tin-lead. The cross-sectional analysis of tin is along the length direction and can distinguish between the bend and the straight part; and the tin-copper cross-sectional analysis is along the width direction.
3, electroplating processability: The actual investigation and evaluation of the high-speed electroplating production line found that the pure tin process is easier to control than tin-lead and tin-copper alloy systems. Compared with the tin-lead system, the pure tin system only needs to control three factors, and because it is a single metal, there is no problem that the alloy mixture is difficult to control. The content of tin and nucleic acid can be easily determined by titration, and the concentration of the additive can also be determined by UV-visible spectrometry. It is also certain that this special pure tin composition is suitable for high-speed electroplating processes, so it will not be necessary to spend extra money on tin-lead plating in the future.
Titration and UV-visible spectrometry can also be used for the chemical control of tin-copper processing. However, alloy mixtures are difficult to control. The content of copper in the electroplating layer must be less than one percent. At present, there is no suitable method to measure the composition. The coating containing tin, lead, and tin can often be measured by an X-ray fluorescence emitter (XRF). This method is not suitable for the tin-copper mixture because it is difficult to detect the copper content of the tin-copper coating on the surface of the copper product because both the plating layer and the main frame contain copper. Therefore, the basic material will have an impact on the measurement results. Merchants recommend a destructive test that dissolves all of the sediment and analyzes the composition by microparticle absorption spectrometry.
4. Humidity Sensitivity: Some conclusions have been drawn by testing packaging products. The current focus is on whether the packaging material itself can maintain a certain degree of integrity after 3X pretreatment at a reflow temperature of 260[deg.] C. (eg no delamination between the mixture and the plating layer). Unprocessed biphenyl compounds in LQFP packages can withstand 3 levels of pretreatment. The raw OCN component in MQFP/PLCC can only withstand 4 levels of pretreatment.
in conclusion
The test results clearly show that pure tin is a reasonable solution for lead-free packaging challenges. It can be stored for 672 hours at 85°C/85% relative humidity or 6 to 18 months at 50°C/85% relative humidity with no whisker growth. The reliability of temperature cycles, pressure tolerance, humidity, and high temperature storage is still being further measured. Further research is needed on how to achieve lower reflow temperatures and broader reliability.
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