This project consists of three parts. The first part is aimed to summarize list of actual packaging systems and especially systems using 3D construction. Project continues in the second part, which is more practical and contains design and production of organic and inorganic testing substrates for lead-free soldered 3D structures. Last experimental part is about tests performed on soldered substrates and evaluation of results of these practical tests.

This work is considered about changes of electric conductivity in lead-free soldered joint's affected by current and thermal stress. The theoretical part describes factors influencing the solder joint electric conductivity and solder joint reliability. The basis of the practical part is the design of the testing method of the soldered joint's electric conductivity. The aim of this part is to measure and observe changes of solder joint electric conductivity after current and thermal stress in various material a procedural combinations.

The thesis deals with problems concerning lead free soldering especially the study of the structure of solder joints and their reliability. The thesis evaluates lead free solder alloys. The theoretical part includes basic principles of soldering and methods of investigating solder joints reliability. The experimental part deals with the impact of water cooling and vibration on solder joint structure. Both methods are tested and are evaluated with regard to their reliability. The used tests include X-ray inspection, optical inspection, mechanical tests, investigating joint structure with electrone microscope.

This research work is dealing with impact and size of the thermoelectric that may influence DC circuits. Main part of this thesis is to build experimental equipment for measurement of the thermoelectric and following usage this equipment for detection of the size the thermoelectric voltage for lead and lead-free solders. The theoretical part of this work deals with creation and usage of the thermoelectric in electrical engineering industry. In this particular part of this work is an example how the thermoelectric influence DC circuits. Then I describe thermoelectric generation from the motherboard to the die. The practical part of this thesis is focused on the development of the equipment for measuring of the thermoelectric of different types of materials. The Thermoelectric has been measured on two types of the lead, six types lead-free solders and on four types of the thermocouple wires. It has been measured within the range from 0°C to 80°C. In the end of this work is summary, where is reviewed witch of solders is the best for an applications affected by the thermoelectric.

The project contains theoretical research of electrotechnical manufacture for lead-free reflow soldering. It contains characterization of soldering processes. Includes variations of solder paste printing, principles of part placing and also reflow soldering process. The project appoints possibilities of testing solder joints strength, mainly focused on mechanical vibrations. It describes a design and preparation of solder joint strength test methods by mechanical vibrations. It compares influence of vibrations on part types and solder alloys.

The Master thesis deals with technology of mounting QFN packages on to the printed circuits boards. Describes also influence of shape and size of soldering pads and the amount of soldering paste with respect to the quality and the reliability. In first part overview of existing packages is summarised. Second part describes design of testing board and the factors which leads to eliminating errors during manufacturing process.

The endeavor to have more efficient solar cells and as environmentally beneficial as possible are the driving forces for this work. The way to reach this is by research to better the understanding of the mechanisms and parameters that govern the performance of solar cells. New materials are essential to develop because the current ones lack stability and are water, temperature and UV-radiation sensitive. In this work the lead (Pb2+), which is poisonous and hazardous is intended to be replaced in the organic metal halide (OMH) perovskite structure. This is tested with gold or silver combined with bismuth and silver by itself. Also trimethylsulfonium gold or silver iodides are investigated. The methylammonium cation is also substituted to cesium. The perovskite material both absorbs light and transports charges in the solar cells. Materials based on AuI/AgI, BiI3 and CH3NH3I and AuI/AgI and [Me3S]I and AgI, BiI3 and CsI were synthesized and analyzed by XRD on thin film and mesoporous substrate and Raman spectroscopy to determine material structure and bonding. J-V measurements were performed to see the function in solar cells. After this conductivity and absorption parameters were determined by an electrical conductivity test and UV-vis absorption spectroscopy. XRD measurements indicate that the perovskite structure could have been obtained because the materials match with the XRD spectra of [20] foremost T3, T5 and T6, Cs1 and Cs2. In T7 some new structure is formed. The bismuth could be partially substituted by silver as the metal cation. The samples are quite amorphous, but still containing crystalline peaks, the product material could be a mixture of a crystalline and an amorphous phase. The crystalline phase could have the desired perovskite structure. To have mesoporous TiO2 as substrate seem to enhance a more crystalline structured material. All the materials seem to have formed some new structures because the pure reactants does not seem to be present, exceptions could be P1 and T1 that contained AuI. The change of cation from methylamine to cesium though results in a shift of the peak positions because of the change of cation size as in [20], but the structure is most likely the same. Raman spectroscopy indicate that there is a change in structure, some new bond being present, when increasing the methylamine ratio for the presumed methylammonium silver bismuth iodide perovskites. This concerns materials T5, T6, T7 with increasing ratio of methylamine. This new bond is most pronounced in T7 where the methylamine content is the highest. Both Silver and bismuth iodide bonds seem to be present and cannot be coupled to be the pure reactants recrystallizing and some new bonds of these are present in all materials to some extent. The organic bond vibration has low intensity and might indicate that there is not so much organic cation present in the product and thus the probability of having the desired product anion decreases. The solar cells made with Spiro-OMeTAD were 700-4000 times more efficient than those made with Sulphur polymer HTM. Solar cells made with Spiro-OMeTAD as HTM gives slightly higher efficiency when increasing the methylammonium cation ratio. For cesium as cation the combined metal cation constellation with bismuth and silver gives a little higher efficiency than bismuth alone. Methylammonium as cation gives a higher efficiency than cesium. Solar cells made with Sulphur polymer HTM show approximately 3-30 times higher efficiency with methylammonium as cation compared to cesium as cation. HTM material seem to affect the perovskite material making some of the cells completely transparent and some of them paler, water in the solvent chlorobenzene can be a possible explanation. The transparency can be the reason for the low efficiency obtained for the solar cells. Also the measurement methodology of these solar cells can also have been false, measuring the contacts, and the etching procedure could be another source of this. The solar cells had quite low efficiencies compared to [20], although same presumed material and procedure has been used and thus there might be something wrong in the accuracy of the manufacturing. The cells should probably been made several times and possible sources of error should be analyzed and corrected for. The materials were all relatively conductive. P1 gave the highest conductivity, almost three times higher than for methylammonium lead iodide that has a conductivity of 1,1x10-4 s/cm [3]. Increasing the methylammonium ratio gave an increase of the conductivity both with bismuth and silver as metal cations and silver alone. The increase of the methylammonium ratio might result in a new structure formed which has lattice planes that are more conductive. A change of gold to silver for the trimethylsulfonium iodide materials gave a large decrease in conductivity. The materials have different absorption curves meaning that they have different bandgaps and this indicates differences in structure. The bandgaps of all materials are indirect contrary to what is proven to be the case for perovskites that are believed to have direct bandgaps in general. To have indirect bandgaps requires a shift in momentum in the electronic transitions and is not as beneficial as having direct bandgaps. Compared to methylammonium lead iodide that has a direct bandgap of 1,6 eV, the bandgaps are at least 0,5 eV higher and range between 2,2-2,36 eV. P1 had a low bandgap of 1,6 eV meaning it absorbs a wide range of wavelengths. The conductivity does not seem to be the obstacle and the cells that are not transparent absorb light. It is highly possible that the low solar cell performance, at least to a certain extent, has to do with the production process. The low scan rate could also affect the low efficiencies and HTM Spiro-OMeTAD should be used. Currently the efficiency of the perovskite materials with silver/bismuth, gold/bismuth and silver are too low, and not able to substitute lead in the perovskite structure solar cells. Neither trimethylsulfonium gold or silver iodide cells nor cesium perovskites have enough efficiency at present. The conductivities for the materials are promising and the materials that are not completely transparent absorb light. / Strävan att utveckla effektivare solceller och så miljövänliga som möjligt är drivkrafterna för det här arbetet. För att uppnå detta krävs forskning för att förbättra förståelsen för vilka mekanismer och parametrar som styr hur väl solcellerna fungerar. Det är nödvändigt att ta fram nya material, då de nuvarande brister i stabilitet, de är framförallt känsliga för vatten, temperatur och UV-strålning. I det här arbetet är syftet att byta ut bly (Pb2+), som är giftig och kopplad till hälsorisker, i den organiska metall halid (OMH) perovskit strukturen. Detta görs med guld eller silver i kombination med vismut och silver självt. Även trimetylsulfonium- guld eller silver undersöks. Metylammonium katjonen substitueras också mot cesium. Perovskit material absorberar både ljus och transporterar laddningar i solceller. Material baserade på AuI/AgI, BiI3 och CH3NH3I and AuI/AgI och [Me3S]I and AgI, BiI3 and CsI syntetiserades. Dessa analyserades, med XRD på dels ett substrat av tunn film och dels ett mesoporöst och Raman spektroskopi, för att bestämma strukturen på materialet och bindningar. J-V mätningar utfördes för att se hur materialen fungerade som solceller. Efter detta utfördes mätningar av konduktiviteten och absorptions parametrar bestämdes genom ett elektriskt konduktivitetstest respektive UV-vis absorptions spektroskopi. XRD mätningarna indikerar att perovskit strukturen kan ha erhållits eftersom spektrumen överensstämmer med de i [20], framförallt för T3, T5 och T6, Cs1 och Cs2. I T7 bildas någon ny struktur. Vismut skulle kunna vara delvis utbytt mot silver som metalkatjon. Proven är relativt amorfa, men uppvisar kristallina toppar och produkten skulle kunna vara en blandning av en kristallin och amorf fas, där den kristallina fasen skulle kunna ha den eftersträvade perovskit strukturen. Mesoprös TiO2 som substrat verkar öka graden av kristallinitet hos materialen. Samtliga material verkar ha bildat någon ny struktur eftersom reaktanterna i sin rena form inte verkar finnas. Undantag skulle kunna vara P1 och T1, vilka innehåller AuI. Bytet av katjon från metylammonium mot cesium resulterar i ett skifte av topparna troligen beroende av skillnaden i storlek mellan katjonerna, liksom påvisas i [20], men strukturen är förmodligen densamma. Raman spektroskopin indikerar en förändring i strukturen, någon ny bindning finns, hos materialen när metylammonium andelen ökas för de förmodade metylammonium silver vismut jodid perovskiterna. Detta gäller materialen T5, T6, T7, där andelen metylammonium ökar. Den nya bindningen är mest uttalade i T7, där metylammonium andelen är den högsta. Både silver och vismut jodid bindningar verkar finnas och kan inte kopplas till att de rena reaktanterna har rekristalliserats och nya bindningar av dessa finns i alla material till en viss grad. Den organiska bindningens vibration har låg intensitet och kan tyda på att det inte finns så mycket organisk katjon i produkten och således minskar sannolikheten att ha den eftersträvade anjon produkten. Solcellerna gjorda med Spiro-OMeTAD var 700-4000 gånger mer effektiva än dom gjorda med Svavel polymer HTM. För solcellerna gjorda med Spiro-OMeTAD som HTM ger en ökning av metylammonium katjon andelen en ökad effektivitet. För cesium som katjon med den kombinerade metalkatjon konstellationen med vismut och silver, blir effektiviteten högre än om vismut är metalkatjon självt. Metylammonium som katjon ger en högre effektivitet än cesium. Solceller gjorda med Svavel polymer HTM visar ungefär 3-30 gånger högre effektivitet med metylammonium som katjon jämfört med cesium som katjon. HTM materialet verkar påverka perovskit materialet och göra några av cellerna helt transparenta och de andra blekare. Klor benzen användes som lösningsmedel och denna kan ha innehållit vatten och kan vara orsaken till färgskiftningen. Detta kan vara orsaken till den låga verkningsgraden som erhölls för solcellerna. En annan möjlig förklaring skulle kunna vara metoden för mätningarna. Denna kan ha varit felaktig, då kontakten troligen har varit det som har mätts och etsningsprocessen skulle kunna vara en orsak till detta. Solcellerna uppvisar ganska låg effektivitet i jämförelse med [20], trots att samma material och procedur har använts och således kan det vara något fel i precisionen av framställningen. Cellerna skulle förmodligen gjorts om ett antal gånger och möjliga felkällor borde utretts och åtgärdats. Materialen var överlag relativt konduktiva. P1 gav den högsta konduktiviteten, nära tre gånger högre än metylammonium bly jodid, som har en konduktivitet på 1,1x10-4 s/cm [3]. En ökning av andelen metylammonium gav en ökning av konduktiviteten både med vismut och silver som metalkatjon och silver självt. Ökningen av andelen metylammonium skulle kunna resultera i ett en ny struktur uppkommer som har plan som är mer konduktiva. Utbytet av guld mot silver för trimetylsulfonium jodid materialen gav en markant sänkning av konduktiviteten. Materialen har olika absorptionskurvor vilket innebär att de har olika bandgap och detta indikerar olikheter i strukturen. Bandgapen för alla material är indirekta, trots att bandgapen för perovskiter i regel är direkta. Att ha indirekta bandgap kräver ett skifte i momentum i de elektroniska energiöverföringarna och är inte så fördelaktigt som att ha direkta bandgap. I jämförelse med metylammonium bly jodid, som har ett direkt bandgap på 1,6eV, är bandgapen minst 0,5 eV högre och varierar mellan 2,2-2,36 eV. P1 hade ett lågt värde på bandgapet, 1,6 eV, vilket innebär absorption av ett brett spektrum av våglängder. Konduktiviteten verkar inte vara den faktor som är orsaken till den låga effektiviteten hos solcellerna och de celler som inte är transparenta absorberar ljus. Det är högst troligt att den låga effektiviteten har sin förklaring, åtminstone delvis, i produktionsprocessen för solcellerna. Den relativt låga skanningshastigheten kan också vara en orsak för den låga effektiviteten och HTM Spiro-OMeTAD bör användas. I dagsläget är effektiviteten för perovskitmaterialen med silver/vismut, guld/vismut och silver för låg och har inte möjlighet substituera bly i perovskit solceller. Inte heller trimetylsulfonium guld eller silver jodid cellerna och inte heller cesium perovskiternas effektivitet räcker till i dagsläget. Konduktiviteten för materialen är lovande och materialen som inte är transparenta absorberar ljus.

Avzinkningshärdiga och blyfria mässingslegeringar används i stor utsträckning för att ersätta blyinnehållande mässingslegeringar som används för dricksvattensapplikationer. På grund av det begränsade antalet korrosionsstudier av dessa legeringar är syftet med denna studie att belysa hur vattensammansättning, temperatur och exponeringstid kan påverka legeringarnas korrosionsegenskaper. Tre avzinkningshärdiga mässingslegeringar studerades i kranvatten; två blyfria mässingslegeringar (CW511L och CW724R) och en blyinnehållande mässingslegering (CW602N) som betraktades som ett referensmaterial. En kombination av elektrokemiska, mikroskopiska och ytanalystekniker användes för att utforska korrosionstyp, mekanismer samt korrosionshastighet. Även om samtliga legeringar visade godkända egenskaper i avzinkningstestet enligt ISO 6509-1:2014 var målet att bedöma deras korrosionsbeteende i kranvatten. Vattenkemin justerades för att undersöka effekten av pH, kloridkoncentration och alkalinitet hos de tre mässingslegeringarna under kortvarig exponeringstid (24 timmar). Vattnets korrosivitet varierade beroende på mässingslegeringens sammansättning. Det visade sig att CW511L var känsligare för höga kloridkoncentrationer (44.7 mg/L) och hög alkalinitet (310 mg/L) än för lågt pH (6.9). Det motsatta observerades dock för både CW724R och CW602N. Testvattnets aggressivitet påverkades också av temperaturen när den ökades från 22 °C till 50 °C under exponering i 24 timmar. Medan ingen tydlig avzinkning upptäcktes observerades en kombination av både allmän och lokal korrosion i varierande utsträckning mellan de olika legeringarna. Initieringen av det lokala korrosionsangreppet varierade både med testvattnets kemi och med legeringssammansättningen. Medan CW724R och CW602N bägge uppvisade hög känslighet för lokal korrosion i vattnet med högst pH (8.2), var CW511L mer känslig i det vatten med lågt pH (6.9) vid 50 °C. Effekten av exponeringstid undersöktes i vattnet med högst pH (8.2) för de tre mässingslegeringarna upp till 72 dagar. Korrosionshastigheten baserad på viktminskning visade en förväntad hög korrosionshastighet som minskade med kontinuerlig exponeringstid, vilket ledde till en låg korrosionshastighet för alla tre mässingslegeringarna efter 72 dagar. De blyfria mässingslegeringar uppvisade ur detta perspektiv goda korrosionsegenskaper som är konkurrenskraftiga med mässing som innehåller bly. / Dezincification resistant (DZR) and lead-free brass alloys continue to be widely applied replacing lead containing brasses in the drinking water sector. Due to the limited number of corrosion studies of these alloys in tap water, the present thesis was initiated with the aim to understand how the water type, its temperature and exposure duration can affect the corrosion behavior. Three DZR brass alloys were studied in order to evaluate their corrosion behavior in tap water of varying characteristics. The alloys included were two lead-free brasses (CW511L and CW724R) and a leaded brass alloy (CW602N) considered as a reference material. A combination of electrochemical, microscopic and surface analytical techniques were adopted to explore the corrosion form, mechanisms and corrosion rate. While these alloys passed the dezincification test as per ISO 6509-1:2014, the aim was to assess their corrosion performance in tap water. The influence of water chemistry parameters including pH, chloride concentration and alkalinity on the corrosion resistance of the three DZR alloys was investigated in short-term exposures (24 h). Depending on the brass alloy, the corrosivity of the test waters varied. The results show grade CW511L to be more sensitive in tap water of higher chloride concentration (44.7 mg/L) and alkalinity (310 mg/L) compared with low pH (6.9). However, opposite results were obtained for both CW724R and CW602N. The corrosivity of the test water was also affected by the temperature when increased from 22°C to 50°C during 24 h of immersion. While no dezincification features were observed on the surfaces, a combination of general and localized corrosion was observed to a largely variable extent between the alloys. The extent of initiation of localized corrosion varied with test water and alloy composition. While CW724R and CW602N showed similar high susceptibility to localized corrosion in the alkaline (pH 8.2) tap water, CW511L was more prone to pitting corrosion in tap water of low pH (6.9). The effect of exposure duration was explored in the alkaline test water for the three brasses up to 72 days. Corrosion rates based on weight loss showed an expected initial high corrosion rate which declined with continuous immersion, leading to low and similar corrosion rates for all three brass alloys after 72 days. Thus, at given test conditions, the lead-free brasses showed good corrosion behavior being competitive to the performance of lead containing brass. Therefore, lead-free brass alloys are good candidates to substitute lead-containing brasses in tap water applications.

abstract: As the microelectronics industry continues to decrease the size of solder joints, each joint will have to carry a greater current density, making atom diffusion due to current flow, electromigration (EM), a problem of ever-increasing severity. The rate of EM damage depends on current density, operating temperature, and the original microstructure of the solder joint, including void volume, grain orientation, and grain size. While numerous studies have investigated the post-mortem effects of EM and have tested a range of current densities and temperatures, none have been able to analyze how the same joint evolves from its initial to final microstructure. This thesis focuses on the study of EM, thermal aging, and thermal cycling in Sn-rich solder joints. Solder joints were either of controlled microstructure and orientation or had trace alloying element additions. Sn grain orientation has been linked to a solder joints’ susceptibility to EM damage, but the precise relationship between orientation and intermetallic (IMC) and void growth has not been deduced. In this research x-ray microtomography was used to nondestructively scan samples and generate 3D reconstructions of both surface and internal features such as interfaces, IMC particles, and voids within a solder joint. Combined with controlled fabrication techniques to create comparable samples and electron backscatter diffraction (EBSD) and energy-dispersive spectroscopy (EDS) analysis for grain orientation and composition analysis, this work shows how grain structure plays a critical role in EM damage and how it differs from damage accrued from thermal effects that occur simultaneously. Unique IMC growth and voiding behaviors are characterized and explained in relation to the solder microstructures that cause their formation and the possible IMC-suppression effects of trace alloying element addition are discussed. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2019

No description available.