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Apply Low Residue Flux to all the leads on the SMD you're removing
With a soldering iron, melt the low temperature alloy
SURFACE MOUNT TECHNOLOGY
BIRLA INSTITTUTE OF TECHNOLOGY MESRA, RANCHI-835215 SURFACE MOUNT TECHNOLOGY PRESENTED BY:- SUBHENDRA P. SIGNH(BE/1247/2009) PAVAN TEJA NAMMI(BE/1248/2009)
CONTENTS WHAT IS SMT? ADVANTAGES OF SMT TYPES OF SMT SUFACE MOUNT COMPONENTS(SMC) SURFACE MOUNT DESIGN PROCESS OF MANUFACTURE APPLICATIONS OF SMT SUMMARY REFERENCES
WHAT IS SMT ?A method for constructing electronic circuits in which the components (SMC, or Surface Mounted Components) are mounted directly onto the surface of printed circuit boards (PCBs). Electronic devices made for this purpose are called surface-mount devices or SMDs. And this technique is known as Surface Mount Technology
In SMT electronic components are mounted to a printed circuit board. The solder joint forms the mechanical and electrical connection. Bonding of the solder joint is to the surface of a conductive land pattern. Connection does not use through holes or terminals.
ADVANTEGES OF SMT Smaller components. Smallest is currently 0.4 x 0.2 mm. Denser layout Improved shock and vibration characteristics Improved frequency response Easier to shield from EMI / RFI Easier to automate manufacturing Reduced board rework costs and time
• Fewer holes need to be drilled through abrasive boards.• Small errors in component placement are corrected automatically• Components can be placed on both sides of the circuit board.• Lower resistance and inductance at the connection• Better mechanical performance under shake and vibration conditions.• SMT parts generally cost less than through-hole parts.
TYPES OF SMT SMT replaces DIPs(Dual in package) with surface mount components. When attached to PBs, both active and passive SMCs form three major types of SMT assemblies:-1. TYPE I2. TYPE II3. TYPE III
TYPES OF SMT Type I (Full SMT board with parts on one or both sides of the board) Type II (Surface mount chip components are located on the secondary side of the Printed Board (PB). Active SMCs and DIPs are then found on the primary side) Type III (They use passive chip SMCs on the secondary side, but on the primary side only DIPs are used)
SURFACE MOUNT COMPONENTS Chip resistors, capacitors Small outline transistors (SOT) PLCC (plastic lead chip carrier) QFP, SOIC(gull wing) Area array
It depends on a number of factors• Market needs• Function• Package moisture sensitivity• Thermal and solder joints reliability• As the packaging density increases, thermal problems are compounded, with a potential adverse impact on overall product reliability
PROCESS OF SMT ASSEMBLY Solder paste printing or dispensing Component placement Reflow Inspection Rework/backload Cleaning
Solder paste printing or dispensing Solder paste is applied on the board at the areas where SMC’s are to be fixed. Component placement The SMC are then placed on their intended position where the solder paste is printed
Reflow Once parts have been placed on the solder paste bricks, the entire board is placed in an oven and taken through a temperature profile like:
Inspection Look for wrong/misplaced components and poor solder joints Rework/backload Fix problems and add parts that can’t survive the high temperature of the reflow oven Cleaning Wash to remove flux residues
APPLICATIONS OF SMT Used to obtain highly accurate and compact circuit boards Used in power amplifier design and modern communication systems Backlighting of legends and LCDs
SUMMARY Surface Mount Technology is a very reliable technology for designing PCB’s. It provided us high density circuits with proper reliability. It is very accurate and reworks are easy . It has a wide application in industry.