Mohit Final

TABLE OF CONTENTS             

Recap Printed circuit boards(PCBs) Designing of PCB Through Hole Technology and its limitations. Surface mount technology Common SMT packages SMT Components SMT Techniques Summary of SMT techniques Advantages of SMT Disadvantages of SMT Applications Refrences

RECAP  Printed

circuit board(PCB).

 Integrated

circuits

which are soldered on PCBs using through-hole technology.

PRINTED CIRCUIT BOARD  Basic

component.

 Before

PCBs point to point or wire wrap was

used.  Provide

mechanical support and electrically

connect electronic components.  Use

conductive pathways, or traces.

DESIGNING OF PCB

THROUGH-HOLE TECHNOLOGY  Components

are inserted on PCB by making

holes.  Loaded

on one side and soldered on other.

 Soldered

through the leads of the components.

THROUGH-HOLE PCB

SURFACE MOUNT TECHNOLOGY  Method

for constructing electronic circuits.

 Components

are mounted directly onto the

surface.  Electronic

devices so made are called surface-

mount devices or SMDs.  Largely

replaced the through-hole technology

SURFACE MOUNT TECHNOLOGY  Replaced  An

the leads by castellation.

SMT component is usually smaller than its

through-hole.  Components

on both sides of board.

DISADVANTAGES OF HT-TECHNOLOGY  Unwanted

effects are more.

 Drilling

may damage the PCB.

 Electric

connections are weak.

 Single  Large

side usage. in size.

DISADVANTAGES OF HTTECHNOLOGY

COMMON SMT PACKAGES Three popular package: 0603(60

thou long,30 thou wide)

 0805(80

thou long,05 thou wide)

 1206(120

thou long,60 thou wide)

SMT COMPONENTS

SMT PCB

HOW TO SMT (TECHNIQUES)  Fine

tip soldering Uses conventional soldering techniques on a much smaller scale  Hot air reflow Uses soldering paste and hot air to reflow the soldering paste with components preset  Oven reflow Uses soldering paste and reflows entire board

FINE TIP SOLDERING  Conventional

equipment  Causes eye strain  Requires a steady hand

HOT AIR REFLOW  Hot-Air

Rework Station Fine tip solder tools Desoldering tools Hot tweezers Hot air gun

OVEN REFLOW  Typical

Large

Reflow oven and bulky

Expensive

$$$ 

OVEN REFLOW OVERVIEW  After

applying solder paste and setting components, the board is inserted to be “cooked”  End result is a perfectly soldered board for a fraction of the cost (no eye strain either).

OVEN REFLOW STEPS  Apply  Set

soldering paste

IC’s and components

 Cook!  Touch

up using soldering wick to

remove excess solder.

SUMMARY OF TECHNIQUES  Fine

tip soldering is hard, but essential

sometimes  Hot

air reflow is more convenient for

reworking of components  Oven

reflow is great for creating a whole board

at once.

ADVANTAGES OF SMT  Faster

for automatic machine to place.

 Smaller  Less

physical size.

parasitic effects.

 Cheaper.  Components

can be fitted to both sides of the

circuit board.

ADVANTAGES OF SMT  Soldering

and de-soldering is easy.

 Reusability.  Modern

components are available in SMT

form.  Less

loaded.

 Failure

is minimum.

DISADVANTAGES OF SMT  The

initial cost and time of setting up for

production is high.  Mechanically  The

weak.

manufacturing processes for SMT are

much more sophisticated than through-hole boards.

APPLICATIONS  Designing  Military  Small

of hybrid components.

devices and LCCCs.

IC packages.

 Robotics.

FUTURE 

Most aims towards the future in SMT is geared towards: 

  

To evolve solder, to create a newer, better alloy composition to improve performance. The capability to create PCBs smaller and lighter (eventually to the nano scale). Nanotechnology . Bright spot in the world of PCB.

REFRENCES 

     

http://books.google.co.in/books?id=IcxDPA2U6esC&dq=su rface+mount+technology+principles&printsec=frontcover &source=bl&ots=r5hvHGF12s&sig=eSO_N60CRWxaFMybEr kog_3SKAE&hl=en&ei=qxyYSoqKFMONkQXJwMGxBQ&sa=X &oi=book_result&ct=result&resnum=4#v=onepage&q=&f= false www.geocities.com/vk3em/smtguide/SMT-GuideV1-3.PDF www.intel.com/Assets/PDF/pkginfo/ch_07.pdf http://en.wikipedia.org/wiki/Surface-mount_technology www.emeraldinsight.com/ssmt www.geocities.com/vk3em/smtguide/SMT-GuideV1-3.PDF http://en.wikipedia.org/wiki/Printed_circuit_board

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