2013 IEEE 63rd Electronic Components and Technology Conference, 2013
ABSTRACT The work presented in this paper has been carried out in order to find means to improve ... more ABSTRACT The work presented in this paper has been carried out in order to find means to improve the existing methods of board-level drop reliability assessment to better represent the use environment loading conditions of modern portable electronic devices. To provide goals and guidance for the development work, eight commercially available smart phones from different manufacturers were evaluated for their free-fall drop response. The results show that the drop response can be divided conceptually into two parts: (i) forced bending/twisting of the component board at the moment of the impact, and (ii) subsequent (resonance) vibration of the component board. The strain magnitudes caused by the forced bending and twisting were much higher than those by the post impact vibrations. Furthermore, sharp strain peaks were often identified within a few milliseconds from the impacts. The results of the Finite Element simulations show that the distribution of strains on the component boards is highly nonuniform; The regions of high strain are localized because they are caused either by the forced bending (by surrounding covers and frames in part i) or by internal collisions between the component board and the surrounding mechanical structures (sharp strain peaks in part ii). The devices were characterized for maximum strain, average rate to maximum strain, vibration frequencies and maximum value of deceleration. The following goals were set for the development of a board-level drop test methodology: a test board that simulates the response of modern portable products should be able to produce board strain well above 3 500 μ (“micro-strain” = [10-6 m/m]) and mean rate to maximum strain close to 7 s-1. Reaching these objectives requires significant changes to the existing JESD22-B111 approach. An investigation on the effects of the shape of deceleration input pulse was carried out first, followed by modifications for the board support to fur- her increase the maximum strain and the average strain-rate of the JESD22-B111 compliant printed wiring board. The support was modified by replacing the four point supports by line supports at both ends of the rectangular shaped board. This approach can achieve the maximum strains of 5 000 μ when coupled with the optimized deceleration input. In addition to the increased strain and strain-rate, dampening of the board vibration became more effective, which is also in a better agreement with the typical drop response of portable electronic products.
2015 IEEE 65th Electronic Components and Technology Conference (ECTC), 2015
In this study, a novel side-impact test method is developed for shearing-off miniature electromec... more In this study, a novel side-impact test method is developed for shearing-off miniature electromechanical devices from the printed wiring boards (PWBs) of portable products. The test method is implemented by modifying a commercial IZOD pendulum impact test setup. The key modification is the replacement of the instrumented pendulum impactor with an instrumented “striker-bar” design. The pendulum instrumented with the “striker-bar” allows high impact velocity up to 3.54E+3 mm/s, and is specially designed for testing components with very low profile. In this study, this setup is used to test a miniaturized electromechanical devices, such as a micro-switch, whose low profile presents a significant challenge to repeatable side-impact testing. Both overstress impact tests and repetitive impact fatigue tests are conducted, to evaluate the interaction of the different parts of the entire electromechanical assembly, including the solder joints, pins, through-holes and housing of the package. Failure modes are documented and failure envelopes are developed by relating the measured durability to the impact parameters like impact velocity, fracture energy and force impulse.
A consortium composed of industrial and academic representatives has been working on an update fo... more A consortium composed of industrial and academic representatives has been working on an update for the widely-employed JESD22-B111 drop test standard for handheld electronics. To form a better understanding of the drop response of handheld devices, the group performed a product-level shock impact characterization for modern smartphones. The results of the product-level characterization showed that drop impacts frequently produce component board strains above 5000 μ (10 −6 ) and average rates to the maximum strain of above 7 s −1 , which are well above those produced under the impact conditions specified by the JESD22-B111 standard. These results initiated an investigation of ways to increase the maximum board strain and the average rate to the maximum strain. An investigation of the effects of the input deceleration pulse shape was carried out first and the results showed that an increase in the value of maximum deceleration and the duration of the pulse (i.e., an increase in the ch...
The aim of the product level drop response evaluation presented in this paper is to provide goals... more The aim of the product level drop response evaluation presented in this paper is to provide goals and guidelines for the development of a board-level drop test methodology that would better reproduce the field use loading conditions of modern portable electronic devices. Eight commercially available smart phones from different manufacturers were evaluated for their free-fall drop response. For this purpose, miniature accelerometer and strain gauges were attached to various locations on the component board inside the product covers. The maximum strain, average rate to maximum strain, frequency of the effective mode shapes, and maximum deceleration were determined from the measured strain and deceleration histories. The determined values showed significant variation from drop to another and device to another, but it was noteworthy that the extreme magnitude of the strain, average rate to maximum strain, and deceleration can be very high: values as high as 10,000 l (''micro-strain'' = [10 À6 m/m]), 26 s À1 , and 10 kG were measured, respectively. Post analyses of the strain histories revealed that the shock impact response of the devices can be conceptually divided into two consecutive periods: (i) forced high amplitude bending/twisting of the component board at the moment of impact, and (ii) subsequent lower amplitude (resonance) vibration of the component board while the device bounces back from the site of impact. Maximum train values reached during Period (i) were typically much higher than the typical strain peaks during Period (ii). However, during Period (ii) sharp strain peaks were often identified whose maximum value occasionally went well above the maximum value during Period (i). Furthermore, any resonance vibrations initiated by the impact forces were dampened efficiently in all device models. In order to form a better understanding of what is causing the very high strains, the drop response of one of the devices was simulated by employing the Finite Element Method (FEM). The FEM results showed that the regions of high strains are highly localized. During Period (i) they are caused by the forced bending of the board by the surrounding mechanical structures, and during Period (ii) by internal collisions between the vibrating component board and the surrounding mechanical structures. On the basis of the characterization of the commercial portable devices, the following goals were set for the development of a board-level drop test methodology: a test board that simulates the response of portable electronic products to a free-fall drop impact should be able to produce: (1) board strain well above 3500 l and (2) average strain rate as close as possible to 7 s À1. The experimental characterization of the mobile devices was carried out by Aalto University, while the device-level drop impact simulations were performed by Nokia.
Inspection on 95 failed connector contacts of 23 mobile phones shows that the contaminants at the... more Inspection on 95 failed connector contacts of 23 mobile phones shows that the contaminants at the contact areas are formed by various sizes of particles. They are adhered together. It seems that smaller ones accumulate the larger ones. The composition of contaminants is very complex, which include dust particles containing mainly silicates (quartz, mica, feldspar) and calcium compounds (gypsum, calcite and lime), wear debris of surface materials, corrosion products (sulfates, chlorides and oxides of copper and nickel) and high concentration of organics. Organic materials seem to act as adhesives at different temperatures. Contaminants causing failure usually located at or near the wear tracks. The most important function of micro-motion is to move the separated contaminants and accumulate them together at the contact; they also produce wear debris, and destroy the surface metal layer as well. High contact resistance is happened in several small regions at the contaminant that provide high enough thickness. Failure could be happened within very short time period (3-4 months) depends on the high resistance region is formed. Conventional ways of corrosion gas test, sand or artificial dust test, shock and vibration test can hardly simulate the failure of contact occurred in China.
2013 IEEE 63rd Electronic Components and Technology Conference, 2013
ABSTRACT The work presented in this paper has been carried out in order to find means to improve ... more ABSTRACT The work presented in this paper has been carried out in order to find means to improve the existing methods of board-level drop reliability assessment to better represent the use environment loading conditions of modern portable electronic devices. To provide goals and guidance for the development work, eight commercially available smart phones from different manufacturers were evaluated for their free-fall drop response. The results show that the drop response can be divided conceptually into two parts: (i) forced bending/twisting of the component board at the moment of the impact, and (ii) subsequent (resonance) vibration of the component board. The strain magnitudes caused by the forced bending and twisting were much higher than those by the post impact vibrations. Furthermore, sharp strain peaks were often identified within a few milliseconds from the impacts. The results of the Finite Element simulations show that the distribution of strains on the component boards is highly nonuniform; The regions of high strain are localized because they are caused either by the forced bending (by surrounding covers and frames in part i) or by internal collisions between the component board and the surrounding mechanical structures (sharp strain peaks in part ii). The devices were characterized for maximum strain, average rate to maximum strain, vibration frequencies and maximum value of deceleration. The following goals were set for the development of a board-level drop test methodology: a test board that simulates the response of modern portable products should be able to produce board strain well above 3 500 μ (“micro-strain” = [10-6 m/m]) and mean rate to maximum strain close to 7 s-1. Reaching these objectives requires significant changes to the existing JESD22-B111 approach. An investigation on the effects of the shape of deceleration input pulse was carried out first, followed by modifications for the board support to fur- her increase the maximum strain and the average strain-rate of the JESD22-B111 compliant printed wiring board. The support was modified by replacing the four point supports by line supports at both ends of the rectangular shaped board. This approach can achieve the maximum strains of 5 000 μ when coupled with the optimized deceleration input. In addition to the increased strain and strain-rate, dampening of the board vibration became more effective, which is also in a better agreement with the typical drop response of portable electronic products.
2015 IEEE 65th Electronic Components and Technology Conference (ECTC), 2015
In this study, a novel side-impact test method is developed for shearing-off miniature electromec... more In this study, a novel side-impact test method is developed for shearing-off miniature electromechanical devices from the printed wiring boards (PWBs) of portable products. The test method is implemented by modifying a commercial IZOD pendulum impact test setup. The key modification is the replacement of the instrumented pendulum impactor with an instrumented “striker-bar” design. The pendulum instrumented with the “striker-bar” allows high impact velocity up to 3.54E+3 mm/s, and is specially designed for testing components with very low profile. In this study, this setup is used to test a miniaturized electromechanical devices, such as a micro-switch, whose low profile presents a significant challenge to repeatable side-impact testing. Both overstress impact tests and repetitive impact fatigue tests are conducted, to evaluate the interaction of the different parts of the entire electromechanical assembly, including the solder joints, pins, through-holes and housing of the package. Failure modes are documented and failure envelopes are developed by relating the measured durability to the impact parameters like impact velocity, fracture energy and force impulse.
A consortium composed of industrial and academic representatives has been working on an update fo... more A consortium composed of industrial and academic representatives has been working on an update for the widely-employed JESD22-B111 drop test standard for handheld electronics. To form a better understanding of the drop response of handheld devices, the group performed a product-level shock impact characterization for modern smartphones. The results of the product-level characterization showed that drop impacts frequently produce component board strains above 5000 μ (10 −6 ) and average rates to the maximum strain of above 7 s −1 , which are well above those produced under the impact conditions specified by the JESD22-B111 standard. These results initiated an investigation of ways to increase the maximum board strain and the average rate to the maximum strain. An investigation of the effects of the input deceleration pulse shape was carried out first and the results showed that an increase in the value of maximum deceleration and the duration of the pulse (i.e., an increase in the ch...
The aim of the product level drop response evaluation presented in this paper is to provide goals... more The aim of the product level drop response evaluation presented in this paper is to provide goals and guidelines for the development of a board-level drop test methodology that would better reproduce the field use loading conditions of modern portable electronic devices. Eight commercially available smart phones from different manufacturers were evaluated for their free-fall drop response. For this purpose, miniature accelerometer and strain gauges were attached to various locations on the component board inside the product covers. The maximum strain, average rate to maximum strain, frequency of the effective mode shapes, and maximum deceleration were determined from the measured strain and deceleration histories. The determined values showed significant variation from drop to another and device to another, but it was noteworthy that the extreme magnitude of the strain, average rate to maximum strain, and deceleration can be very high: values as high as 10,000 l (''micro-strain'' = [10 À6 m/m]), 26 s À1 , and 10 kG were measured, respectively. Post analyses of the strain histories revealed that the shock impact response of the devices can be conceptually divided into two consecutive periods: (i) forced high amplitude bending/twisting of the component board at the moment of impact, and (ii) subsequent lower amplitude (resonance) vibration of the component board while the device bounces back from the site of impact. Maximum train values reached during Period (i) were typically much higher than the typical strain peaks during Period (ii). However, during Period (ii) sharp strain peaks were often identified whose maximum value occasionally went well above the maximum value during Period (i). Furthermore, any resonance vibrations initiated by the impact forces were dampened efficiently in all device models. In order to form a better understanding of what is causing the very high strains, the drop response of one of the devices was simulated by employing the Finite Element Method (FEM). The FEM results showed that the regions of high strains are highly localized. During Period (i) they are caused by the forced bending of the board by the surrounding mechanical structures, and during Period (ii) by internal collisions between the vibrating component board and the surrounding mechanical structures. On the basis of the characterization of the commercial portable devices, the following goals were set for the development of a board-level drop test methodology: a test board that simulates the response of portable electronic products to a free-fall drop impact should be able to produce: (1) board strain well above 3500 l and (2) average strain rate as close as possible to 7 s À1. The experimental characterization of the mobile devices was carried out by Aalto University, while the device-level drop impact simulations were performed by Nokia.
Inspection on 95 failed connector contacts of 23 mobile phones shows that the contaminants at the... more Inspection on 95 failed connector contacts of 23 mobile phones shows that the contaminants at the contact areas are formed by various sizes of particles. They are adhered together. It seems that smaller ones accumulate the larger ones. The composition of contaminants is very complex, which include dust particles containing mainly silicates (quartz, mica, feldspar) and calcium compounds (gypsum, calcite and lime), wear debris of surface materials, corrosion products (sulfates, chlorides and oxides of copper and nickel) and high concentration of organics. Organic materials seem to act as adhesives at different temperatures. Contaminants causing failure usually located at or near the wear tracks. The most important function of micro-motion is to move the separated contaminants and accumulate them together at the contact; they also produce wear debris, and destroy the surface metal layer as well. High contact resistance is happened in several small regions at the contaminant that provide high enough thickness. Failure could be happened within very short time period (3-4 months) depends on the high resistance region is formed. Conventional ways of corrosion gas test, sand or artificial dust test, shock and vibration test can hardly simulate the failure of contact occurred in China.
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