Surface Mount Technology 0701

8/13/2019 Surface Mount Technology 0701

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Advancements in the process of

SMT assembly



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 density boards 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.



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



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.



Types of SMT

Type 1 SMT



Type 2&3



Surface mount components

Chip resistors, capacitors

Small outline transistors

PLCC (plastic lead chip carrier)

QFP,SOIC (gull wing)

DIP (dual in line package)



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.



Pick and place machine



Types of soldering

infrared/convective reflow soldering

Wave soldering

Hand soldering



Reflow soldering machine



Reflow soldering process graph



AOI



ICT



Boundary scan test



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.



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

Surface Mount Technology 0701

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