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Undersökning av mekanisk belastning på ytmonterade elektriska komponenter vid screentryckning
University of Skövde, School of Engineering Science.
2016 (Swedish)Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesisAlternative title
Examination of mechanical load on surface mounted electronic devices during screen printing (English)
Abstract [sv]

En studie har genomförts för att ta reda på om det finns någon risk att skada ytmonterade komponenter i screentryckningsprocessen om pneumatiska stöd används. Av den genomförda litteraturstudien framgår det att bara en typ av komponent är angelägen att analysera: keramisk kondensator. Det framgår även att böjning av kretskortet som kondensatorn är monterad på kan leda till att kondensatorn spricker.

För det lastfall som uppstår under screentryckning analyseras kretskortets böjning m.h.a. två metoder; analytisk metod för balk på elastiskt underlag och FEM (finita elementmetoden) med diskreta fjädrar. För dessa beräkningar antas storleken på kretskortet vara 100x40x1,6 mm. Enligt den analytiska metoden beräknas kretskortets utböjning till 0,6 mm jämfört med 0,7 mm för FEM. Skillnaden i resultaten beror på att stöden i den analytiska metoden antas vara ett jämnt utbrett underlag medan i FEM-analysen idealiseras stöden som enskilda fjädrar.

Spänningen i kondensatorn p.g.a. kretskortets böjning har beräknats med analytisk metod och FEM. Den analytiska metoden baseras på balkteori och kondensatorn antas följa kretskortets deformation. I FEM-analysen beaktas även lödfogens deformation. Den analytiska beräkningen ger en mycket hög spänning (705 MPa) vilket beror på att kondensatorns deformation antas följa kretskortets. I verkligheten deformeras lödfogen något vilket dämpar spänningen i kondensatorn, varför FEM-analysen ger ett mer pålitligt resultat och spänningen från den analysen är ca 37 MPa.

Slutsatsen av studien är att de pneumatiska stöden kan användas utan risk för att skada de ytmonterade komponenterna.

Abstract [en]

A study is done to find out if there is any risk to damage surface mounted components with the use of pneumatic supports during screen printing. The literature review suggests that there is only one type of component that is relevant to analyze: MLCC (multilayered ceramic chip capacitor). It is also pointed out that bending of the PCB (Printed Circuit Board) on which the MLCC is mounted may cause it to crack.

For the load case that is present during screen printing, the deflection of the PCB is analyzed using two methods: First an analytical method for beam on elastic foundation and second: FEM (Finite Element Method) with discrete springs as support. For these calculations the size of the PCB is set to have the dimensions 100x40x1.6 mm. According to the analytical method the PCBs deflection is 0.6 mm and the FEM 0.7 mm. The difference in deflection is because the analytical method assumes that the elastic foundation is evenly spread while for the FEM the supports are idealized as discrete springs.

The stress in the MLCC as a result of the PCB bending has been calculated both analytically and with FEM. The analytical solution is based on beam theory and the MLCC is assumed to deform equally to the PCB. In the FEM analysis, the solder joint is also considered. The analytical calculations result in very large stresses within the MLCC (705 MPa) which is due to the assumptions made that the MLCC deforms equally to the PCB. In reality, the solder joint also deforms which dampens the stresses in the MLCC. This is why the FEM analysis gives a more realistic result and the stress is calculated to 37 MPa.

The conclusion of this study is that the pneumatic supports can be used without risk of damaging surface mounted components.

Place, publisher, year, edition, pages
2016. , 28 p.
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:his:diva-12476OAI: oai:DiVA.org:his-12476DiVA: diva2:938059
Subject / course
Mechanical Engineering
Educational program
Mechanical Engineer
Supervisors
Examiners
Available from: 2016-06-16 Created: 2016-06-16 Last updated: 2016-06-16Bibliographically approved

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