2 research outputs found

    Study of ionic contamination in electronic product assembly

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    Dissertação de mestrado em Chemical Analysis and Characterization TechniquesThe ever-growing demand for better PCB (printed circuit board) performance as well as component miniaturization and increasing density, are all challenges the automotive industry is facing nowadays. However, these alterations in the PCB layout alongside changes in production materials and techniques may jeopardize product reliability. One of the factors that has the ability to threaten PCB functioning is the introduction of ionic contaminants that increase the probability of electrochemical reactions and premature circuit failures. Methods have been created along the years in order to evaluate the presence of these contaminants on printed boards; one of them is the ROSE (Resistivity of Solvent Extract) test. This thesis aimed to study the ionic contamination in electronic product assembly using the CM22 contaminometer, a ROSE test machine. Essentially, this project was divided in two studies. The first one was the study of ROSE machine response and establishment of parameters to test its performance at Bosch Car Multimedia Portugal S.A. The results revealed that although the relation between the machine response and the dissolved contamination was linear, there was some disparity in values of PCBs from the same product family. The temperature and regeneration time of the extraction bath were identified as possible influencers of this discrepancy. Further tests showed temperature is not a significant factor for this behaviour and, at lower contamination levels, the regeneration time has little impact. The second study intended to evaluate the ionic contamination levels of printed circuit boards in 5 different stages of their production run. This research revealed that the ROSE levels of the PCBs obtained from the supplier decrease during the first steps of the process. Solder paste application, component insertion and reflow steps do not introduce much ionic residues on the board surface. Yet, the most important conclusion to this study is that the flux used for rework and selective soldering greatly increases surface contamination presence. In conclusion, the CM22 ROSE contaminometer is suitable to monitor processes in assembly plants. It can detect contamination trends at a process line and can be used as process control tool especially in a no-clean soldering process like the one used in Bosch. For this reason, the evaluation of ionic content should be carried out in different stages of PCBA production since it can be very deceptive to do them only after reflow process as it normally done.A crescente demanda por melhor desempenho de PCBs (placas de circuito impresso), bem como a miniaturização de componentes e o aumento da sua densidade, são desafios que a indústria automóvel enfrenta atualmente. No entanto, as alterações no seu design juntamente com as mudanças nos materiais e técnicas de produção podem comprometer a fiabilidade destas placas. Um dos fatores que tem a capacidade de ameaçar o funcionamento de um PCB é a introdução de contaminantes iónicos capazes de criar falhas elétricas no circuito. Vários métodos foram criados para avaliar a presença destes contaminantes em placas impressas; um deles é o teste ROSE (Resistividade do Extrato Solvente). Esta tese teve como objetivo o estudo da contaminação iónica na montagem de produtos eletrónicos utilizando o contaminometer CM22, um dispositivo de teste ROSE. Para isto, primeiro estudou-se a resposta da máquina ROSE e estabeleceu-se parâmetros para testar o seu desempenho na Bosch Car Multimedia Portugal S.A. Os resultados revelaram que embora a relação entre a resposta do aparelho e a contaminação dissolvida seja linear, existiu alguma disparidade nos valores de placas da mesma família. A temperatura e o tempo de regeneração do banho foram identificados como possíveis influenciadores desta discrepância. Testes adicionais mostraram que a temperatura não influencia este comportamento e, em níveis de contaminação mais baixos, o tempo de regeneração tem pouco impacto. O segundo estudo pretendia avaliar os níveis de contaminação iónica de placas de circuito impresso em 5 fases diferentes da sua montagem. Este estudo permitiu verificar que o PCB obtido do fornecedor possui um nível de ROSE que diminui ao longo dos primeiros passos do processo. As etapas de aplicação da pasta de solda, inserção dos componentes e refluxo não introduzem muitos resíduos à superfície da placa. No entanto, a conclusão mais importante deste estudo é que o fluxo usado para retrabalho e soldadura seletiva aumentam muito a contaminação na superfície das placas. Em conclusão, o contaminometer CM22 é adequado para monitorizar os processos de fabrico. Ele pode detetar tendências de contaminação na linha de produção e pode ser usado como ferramenta de controlo de processo, especialmente num processo sem limpeza como o da Bosch. Por esse motivo, a avaliação do conteúdo iónico deve ser realizada em diferentes etapas da produção de PCBAs, dado que pode ser enganoso fazê-lo somente após o refluxo, como normalmente é

    Development of interconnections for mm-wave antenna module package

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    Abstract. The increase in mobile network data usage has led to interests in mm-wave frequencies (for example 26.5–29.5 GHz) on becoming fifth generation (5G) networks in addition to previously used sub-6 GHz frequencies. The advantage of mm-wave frequencies is larger bandwidth, leading to larger throughput with a tradeoff of smaller coverage due to shorter wavelength. The coverage issue can be compensated by using antenna arrays instead of one antenna. There have been some studies about stacking antenna module package vertically on motherboard, and in more advanced approach, the RFIC is integrated into the bottom of the antenna module package. This thesis concentrates on developing the interconnection between two PWBs on mm-wave frequency (26.5–29.5 GHz) between the antenna module and motherboard. More accurately, creating interconnection around via structure, carrying RF-signal from antenna module to motherboard by applying vertical stacking. This method may reduce the overall price of the system, while increasing the level of integration in the system. The overall aim of this thesis was to provide a functional and optimized interconnection method with measurement results and limitations of Nokia Factory. The interconnection can be created by using electromagnetic coupling or galvanic connection. The galvanic connection was chosen for many reasons and different interconnection methods applying galvanic connection were introduced. These methods include LGA and BGA soldering, traditional RF-connector and antenna array connector with 16-ports. After considering the options and Nokia Factory limitations, the most suitable interconnection method turned out to be LGA soldering. The research work includes partial design of antenna module and motherboard, and the optimization for connection. Prototypes were created based on the design, and the measurement results and conclusions of interconnection functionality were provided as well. Six prototypes were made, from which prototypes 3–6 were functional in terms of solder height. The measurement results show that there was variation in matching between different prototypes and between simulation and measurement results. By doing x-ray and failure analysis, a few reasons were found to explain the variation. One reason can be found from voids in signal soldering, which widens the soldering horizontally, leading to decreased matching due to changed solder diameter and asymmetric grounding. However, by utilizing the solder bumping method, the appearance and diameter of voids can be minimized. The conclusion with prototypes was that the system functions well, but improvements are recommended, and simulations should be re-done with modifications from failure analysis. Overall, the aim of the thesis was reached.Antennimoduulipaketin liitäntöjen kehittäminen millimetriaalto taajuuksille. Tiivistelmä. Datankäytön jatkuvan kasvun takia viidennen sukupolven (5G) matkapuhelinteknologian kehitys on keskittynyt aiemmin käytettyjen alle 6 GHz taajuuksien lisäksi uusille, korkeammille, millimetriaaltojen (esim. 26.5–29.5 GHz) taajuuskaistalle. Korkeammat taajuudet tarjoavat mahdollisuuden käyttää suurempia kaistanleveyksiä kasvattaen läpikulkevan datan määrää, mutta sen hintana on signaalin kantomatkan pienentyminen aallonpituuden pienentymisen takia. Kantomatkan lyhenemistä voidaan kuitenkin kompensoida käyttämällä antenniryhmiä yksittäisten antennien asemasta. Antenniryhmien integroinnista systeemiin on tehty erilaisia tutkimuksia, joita ovat esimerkiksi vertikaalinen pinoaminen, jossa antennilevy juotetaan toiselle piirilevylle. Edistyksellisemmässä versiossa kyseisen antennilevyn pohjaan on liitetty RFIC piiri. Tässä diplomityössä tutkittiin kahden piirilevyn välistä liityntäkohtaa vertikaalisella pinoamisella. Liityntäkohta kuljettaa millimetriaaltotaajuista RF-signaalia (26.5–29.5 GHz) antennilevyltä äitilevylle. Kyseisellä rakenteella voidaan saada pienennettyä mahdollisen tuotteen kustannuksia, samalla pienentäen myös sen fyysistä kokoa. Työn tarkoituksena on tarjota Nokialle valmiiksi optimoitu liitäntäratkaisu mittaustuloksineen ja tuotannon rajoitteineen dokumentoituna. Tutkittu liityntäkohta voidaan muodostaa sähkömagneettisella kytkeytymisellä tai galvaanisesti, joista jälkimmäinen on huomattavasti järkevämpi ja tässä työssä on esitetty sille erilaisia vaihtoehtoja, joita on vertailtu toisiinsa. Näihin vaihtoehtoihin sisältyy koneellinen juottaminen LGA tai BGA tavalla, RF-liittimien käyttö ja antenniryhmää varten kehitetty 16 porttinen liitin. Kyseisistä liitäntä vaihtoehdoista parhaaksi ja soveltuvimmaksi osoittautui LGA juotos. Tutkimustyö sisältää antennilevyn ja äitilevyn osittaisen suunnittelun ja optimoinnin, ja sen perusteella tehdyn prototyypin, mittaustulokset ja päätelmät liitynnän toimivuudesta. Prototyyppejä tehtiin kaikkiaan kuusi, joista viimeiset 3–6 olivat onnistuneita juotospaksuuden perusteella. Mittausten perusteella sovituksessa on paljon vaihtelua, jolle löydettiin muutamia syitä röntgen tarkastuksessa ja virheanalyysissa. Näihin syihin sisältyy juotoksesta löytyneet kaasukuplat, jotka johtavat juotoksen laajenemiseen horisontaalisesti, mikä taas heikentää maadoitusta ja täten sovitusta. Juotoksen kaasukuplat voidaan kuitenkin välttää niin kutsutulla juotoksen pallottamisella (Engl. Solder Bumping), jossa kaasukuplia ilmeni huomattavasti vähemmän ja ne olivat pienempiä. Lopputulemana todettiin, että työ on onnistunnut ja prototyyppi on toimiva, mutta tarjotut kehitysideat kannattaa huomioida mahdollisessa jatkokehityksessä ja simuloinnit tulisi tehdä uudelleen virheanalyysistä saaduilla arvoilla ja tiedoilla
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