04-09-2012, 03:27 PM
SURFACE MOUNT TECHNOLOGY
surface mount technology by Udaya.ppt (Size: 302 KB / Downloads: 53)
INTRODUCTION
A goal in the production of electronic industry to make the product smaller and lighter. In other words, the purpose is to add more functions to the same size of the circuit board or to maintain the same function but reduce the surface area. The only way to achieve the goal is to minimize the electronic components, replace the conventional components. As a result, the Surface Mount Technology (SMT) was developed.
Surface Mount Technology is a method whereby electronic circuits are fabricated by assembling specially manufactured components on the surface of, instead in holes of the circuit board. The specially manufactured components are called Surface Mounted Components or Devices.
Previously Through Hole Technology was used.
Assembly of circuits using Through Hole Technology employs components with wire or leaded terminals which are inserted either manually or by automated process through specially drilled and plated holes in PCB.The components are finally fixed by soldering.
ADVANTAGES OF SMT
Reduction in package size resulting in greater functionality in the same board area.
Reduction in noise, this is primarily due to smaller electrical paths compared to leaded components. The low noise contribution is mandatory and is a design feature.
Parasitic inductance and capacitance are substantially lowered due to shorter leads.
Using SMDs on both sides of the board, size is reduced by more than 50%.
A very high level of automation and handling equipment is available for surface mount processing. Component placement equipments is generally faster and more versatile.
DECISION MODEL FOR CHOOSING SMT
Choosing whether or not to implement SMT in new products or even to redesign old products should not be as difficult a decision. If three basic conditions exist, one should be led into SMT:
If the electronic assembly requires higher packaging density so that it can all fit a fixed or limited space.
If performance such as high speed,reduced noise and reduced weight is required on a product can only be achieved by using SMT.
If competition is producing products at quality, cost, and performance levels that cannot be matched using conventional technology.
CAPACITOR
SMD capacitor consists of a rectangular block of dielectric in which a number of interleaved precious metal electrodes are contained. This structure gives rise to a high capacitance per unit volume.
Capacitors are marked with the value and working voltage. There are two basic methods used. One is to include their value in microfarads (m F), and another is to use a code.
Using the first method a marking of 33 6V would indicate a 33 mF capacitor with a working voltage of 6 volts.
An alternative code system employs a letter followed by three figures.A marking of G106 would indicate a working voltage of 4 volts and a capacitance 10^6 Pico farads. This works out to be 10 mF.
CONCLUSION
SMT has come to stay with the world wide adoption of this technology. To catch up with the developed nations, India has to cover a lot of ground in this aspect. The country has to shake itself off from the current dependency on through-hole PCBs. This technology is capital intensive. A sustained infrastructure, R&D and finance are needed for both government and big industrial firms to enable the industry attain world standards.
surface mount technology by Udaya.ppt (Size: 302 KB / Downloads: 53)
INTRODUCTION
A goal in the production of electronic industry to make the product smaller and lighter. In other words, the purpose is to add more functions to the same size of the circuit board or to maintain the same function but reduce the surface area. The only way to achieve the goal is to minimize the electronic components, replace the conventional components. As a result, the Surface Mount Technology (SMT) was developed.
Surface Mount Technology is a method whereby electronic circuits are fabricated by assembling specially manufactured components on the surface of, instead in holes of the circuit board. The specially manufactured components are called Surface Mounted Components or Devices.
Previously Through Hole Technology was used.
Assembly of circuits using Through Hole Technology employs components with wire or leaded terminals which are inserted either manually or by automated process through specially drilled and plated holes in PCB.The components are finally fixed by soldering.
ADVANTAGES OF SMT
Reduction in package size resulting in greater functionality in the same board area.
Reduction in noise, this is primarily due to smaller electrical paths compared to leaded components. The low noise contribution is mandatory and is a design feature.
Parasitic inductance and capacitance are substantially lowered due to shorter leads.
Using SMDs on both sides of the board, size is reduced by more than 50%.
A very high level of automation and handling equipment is available for surface mount processing. Component placement equipments is generally faster and more versatile.
DECISION MODEL FOR CHOOSING SMT
Choosing whether or not to implement SMT in new products or even to redesign old products should not be as difficult a decision. If three basic conditions exist, one should be led into SMT:
If the electronic assembly requires higher packaging density so that it can all fit a fixed or limited space.
If performance such as high speed,reduced noise and reduced weight is required on a product can only be achieved by using SMT.
If competition is producing products at quality, cost, and performance levels that cannot be matched using conventional technology.
CAPACITOR
SMD capacitor consists of a rectangular block of dielectric in which a number of interleaved precious metal electrodes are contained. This structure gives rise to a high capacitance per unit volume.
Capacitors are marked with the value and working voltage. There are two basic methods used. One is to include their value in microfarads (m F), and another is to use a code.
Using the first method a marking of 33 6V would indicate a 33 mF capacitor with a working voltage of 6 volts.
An alternative code system employs a letter followed by three figures.A marking of G106 would indicate a working voltage of 4 volts and a capacitance 10^6 Pico farads. This works out to be 10 mF.
CONCLUSION
SMT has come to stay with the world wide adoption of this technology. To catch up with the developed nations, India has to cover a lot of ground in this aspect. The country has to shake itself off from the current dependency on through-hole PCBs. This technology is capital intensive. A sustained infrastructure, R&D and finance are needed for both government and big industrial firms to enable the industry attain world standards.