The analysis of SMD resistor arrays soldered by Sn96 Ag3,5 Cu 0,5 and Sn42 Bi57.6 Ag0.4 in surface mount assembly.

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This article deals with the area of solder joints reliability and narrower focus is on using ANSYS simulation software and fatigue models for estimation of reliability of solder joints. The text describes real reliability of SMD resistor arrays 0603 and therefore there are set conditions of thermal cycling in thermal chamber. Results obtained by thermal cycling and measuring are compared with results obtained by computer simulations in ANSYS. The purpose of this comparison is to show the usefulness of computer simulations for this type of application and find out for differences between simulations and real measurements. There are further included two types of solder pastes for comparison and monitoring options in simulation. In the conclusion the outputs of simulations and results of practical measurements are evaluated and described. The reliability of solder joints is an area of electronic manufactory and its importance and significance is increasing due technological process becomes more complex. There are growing demands on the correct definition of technological processes because new types of solder alloys is need to implement to process. The requirement and origins of these changes is in enviromental issues and reducing of power consumption during process of soldering and electronic manufactory. Therefore arcticle discussed reliability of lead-free solder joints with two types of solder pastes which are standard and well known solder paste SAC305 (Sn96 Ag3,5 Cu0,5) and relatively recently used bismuth solder paste (Sn42 Bi57.6 AgO.4). These pastes are used for soldering of resistors arrays 8 x 0603 and each paste is on 30 testing boards due standard IPC-9701. This standard is prerequisite for testing and thermal cycling profile is set by him. There is assumed thermal cycling in thermal chamber in range from -40 o c to 125 o c with 30 minutes of time dwell on minimal and maximal temperature. Another part of experiment is realizing of several computer simulations in ANSYS for comparison with results obtained by practical measurements. Computer analysis includes all parts of electronic assembly as in the case of practical experiments. This means that there were created models of solder joints and resistor arrays and these models are supplemented by FR-4 substrates and cooper pads in the whole assembly. Results of simulation show the most stressed areas in solder joint and further differential stress is analyzed, which is depending on position of soldered joint in resistor array. The aim of simulations is also comparison and analysis of situation in two types of solders — Sn 96 Ag3,5 CuO,5 and Sn42 Bi57.6 Ag0.4 and obtain some conclusions about their reliability in surface mount assembly. The prerequisite for conditions of stress is thermal cycling according to standard IPC-9701 and selected es of strength tests.

Ansys, Reliability test, Solder, SAC305, IPC-9701

NOVOTNÝ, V.; SKÁCEL, J.; ŠANDERA, J.

1. 12. 2016

978-80-214-5416-3

2nd IMAPS Flash Conference 2016, Book of abstracts

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