Surface mount devices, Physics

Surface Mount Devices (SMDs) are new components designed with soldering pads or short leads. They are much smaller in size as compared to leaded components. The SMDs are directly attached or inserted on the surface of the PCB and then soldered. In the conventional PCB assembly method, the components have leads for insertions into the holes made for the purpose into the boards and are soldered on opposite side of the board. But in surface mount device the components or devices are called surface mount components have leads small then the conventional components which can be soldered on the foot print of the broad directly. In other words in surface mount technology, holes are not drilled and components (specially manufactured) are soldered on the copper side of the board. Chip capacitors, chip resistors, chip inductors are the examples of passive SMDs, while SO-8, So-28, SOT-23 chip carriers are examples of active SMDs. The chip capacitors are multi layer ceramic in value from 1Pf to 1μf or tantalum type with value from 0.22μf to 10μf. The chip resistors are either thick film or thin film type and are available with 1% accuracy. Chip inductors of few mH are available.

ADVANTAGES OF SMDs:

Reduced size and weight. Lower cost. Save lead pre-forming. Components can be maintained from both sides of PCB. Automated high yield production. One machine places most of the components. Smaller production and small area. Smaller size, leadless, low cost. Improved high frequency performance. High dimensions standards. Short interconnections. Better performance. Improved area efficiency. Easy to use computer aided design and manufacture method.

DISADVANTAGES OF SMDs:

Repairs difficult. Generally ultra low power products. Completely new production method and investment. Very high starting costs. New technology, new reliability profile, new problems. Investment in quantity and reliability testing. Difficult to assemble odd shaped components. Must use tape mounted components. Totally new specifications. Needs new manufacturing facilities. Limited power handling. Bread boarding is difficult due to greater power density. PCB heats up. Need new interconnection systems. Unavoidable temperature gradients.   

Posted Date: 7/9/2012 3:59:02 AM | Location : United States







Related Discussions:- Surface mount devices, Assignment Help, Ask Question on Surface mount devices, Get Answer, Expert's Help, Surface mount devices Discussions

Write discussion on Surface mount devices
Your posts are moderated
Related Questions
Q The refractive index of a medium is √3. Compute the angle of refraction if the un-polarised light is incident on it at the polarizing angle of the medium. μ = tan i p = √3

Wave-particle duality: The principle of quantum mechanics that implies that light (and, indeed, all other subatomic particles) sometimes work as a wave, and sometime like a pa


i want to know about not gate

Difference among sound and light waves: (i) For propagation of sound rays material phase is required but no material medium is needed for light waves. (ii)Sound rays are long

Demonstrate resonance and forced vibrations Consider four simple pendulums P,Q,R and S suspended from horizontal stretched rubber card AB. Let the lengths of pendulums p and R

Davisson-Germer experiment (C.J. Davisson, L.H. Germer; 1927) An experiment which conclusively confirmed the wave nature of electrons; diffraction patterns were observed throu

A scooterist is racing at a speed of 72 km per hour. If the radius of the wheel is 20 cm, find the angular speed of the wheels.   Ans) 72kmph=20m/s 20cm=0.2m; v=rw w=v/r w=20/0

1. Two trucks are connected by a rope. The rope is attached to a winch on one of the trucks so that the trucks are being pulled together slowly as the winch pulls in the rope. For