surface mount technology 0701

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    Advancements in the process of

    SMT assembly

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    Abstract As the demands of small light camcorder, cellular phones and other

    electronic devices have been increased the manufacturing technology used

    in the assembling of printed circuit boards has become an important

    criterion. Surface Mount Technology is an innovative trend in the field of

    printed circuit .This technology reduces size and weight of PCBs. SMT also

    provides improved shock and vibration resistance due to lower mass of

    components. The smaller lead lengths of surface mount components reducethe parasitic losses and provide more effective decoupling. The usage

    automatic machines improved the standards of PCB assembling and then

    process became easier and accurate than the through hole technology. In

    SMT reflow soldering technique is mostly used now a days. The testing

    stage of PCB is the crucial stage. Because of requirement of high densityboards we cannot only use normal physical access for testing. So we need to

    adopt some new advanced technologies like MDA and boundary scan which

    will work in coordination with automated machines in addition.

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    Contents What is SMT

    Types of SMT

    Surface mount component (SMC)

    Factors effecting Surface mount design

    Types of soldering

    Inspection

    ICT

    Conclusion

    References

    Learning outcome

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    What is SMT A method of constructing electronic circuits in which the components

    (SMC) are directly mounted onto the surface of PCBs.

    Electronic devices made for this purpose are called surface mount devices

    (SMT).And this technique is known as SMT.

    In SMT both both SMC and normal THT components are used.

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    Types of SMT

    Type 1 SMT

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    Type 2&3

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    Surface mount components

    Chip resistors, capacitors

    Small outline transistors

    PLCC (plastic lead chip carrier)

    QFP,SOIC (gull wing)

    DIP (dual in line package)

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    Factors effecting surface mount designIt depends on a number of factors

    Land patterns.

    The type of SMT process used.

    Packing moisture sensitivity.

    Solder joints reliability.

    Test nodes.

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    Pick and place machine

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    Types of soldering

    infrared/convective reflow soldering

    Wave soldering

    Hand soldering

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    Reflow soldering machine

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    Reflow soldering process graph

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    AOI

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    ICT

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    Boundary scan test

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    Conclusion SMT is more advantages than the conventional circuit board. Because it

    reduces the size of circuit board, cost, weight etc. And the new automated

    machines easier our work and make it more accurate. Due to above

    advantages SMT circuit can be mount on the coin or on the postal stamp.

    Also the circuit can be mounted on both sides of the circuit board. So now a

    days it is used in mobile, calculator or the circuit where small space circuit

    is required. But this physical test access does not give accurate results forlatest and some double sided PCBs so we need to adopt latest technology

    like boundary scan test access which can detect line faults, short faults and

    open faults etc. The AOI machine can work in integration with boundary

    scan test access which is very helpful in detecting faults in initial stages

    itself.

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    References E-BOOK ON SURFACE MOUNT TECHNOLOGYCOMPILED BY DR.

    KANTESH DOSS ELCOTEQ, INC.

    MIRTEC automatic machines user manual.

    www.logextechno.com

    Non-Contact Test Access for Surface Mount Technology IEEE 1149.1-1990

    www.radioelectronics.com

    Surface Mount Technology: Principles and Practice by Ray P. Prasad

    The Electronic Packaging Handbook edited by Glenn R. Blackwell

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