Çağatay Taylan TAN 030070119 7th week

Hand Soldering
Hand soldering involves a skilled operator using a soldering iron to make circuit connections.Compared to wave soldering, hand soldering is slow since each solder joint is made one at a time.As a production method , it is generally used only for small lot production and for rework.As with other manual tasks ,human error can result in quality problems.Hand soldering is sometimes used following wave soldering to add delicate components that would be damaged in the harsh environment of the wave soldering chamber.Manual methods have certain advantages in PCB assembly that should be noted :1)Heat is localized and can be directed at a small target area ; 2)Equipment is inexpensive compared to wave soldering ;3)Energy consumption is considerably less.

(Fundamentals of Modern Manufacturing.Materials,processes and system 3rd edition, Mikell Groover, p. 844) 00.42

Wave Soldering
Wave soldering is a mechanical technique in which printed circuit is boards containing inserted components are moved by conveyor over a standing wave of molten solder.The position of the conveyor is such that only the underside of the board ,with component leads projecting through the holes, is in contact with the solder.The combination of the capillary action and the upward force of the wave cause the liquid solder to flow into the clearances between leads and through-holes to obtain a good solder joint.The tremendous advantage of wave soldering is that all of the solder joints on a board are made in a single pass through the process.

(Fundamentals of Modern Manufacturing.Materials,processes and system 3rd edition, Mikell Groover, p. 844) 00.49

Solder Paste

Solder paste is a suspension of solder powders in a flux binder.It has three functions 1)It is solder -typically %80 to %90 of total paste volume 2)It is the flux and 3)It is the adhesive that secures the components to the surface of the board.Methods of applying the solder paste to the board surface include screen printing and syringe dispensing.Properties of the paste must be compatible with these application methods, the paste must flow yet not be so liquid that it spreads beyond the localized area where it is applied.
After solder paste application components are placed on the board by the same type of onsertion machines used with the adhesive bonding assembly method.A low temperature baking operation is performed to dry the flux binder;this reduces gas escape during soldering.Finally the solder reflow process heats the solder paste sufficiently that the solder particles melt to form a high-quality mechanical and electrical joint between the components leads and the circuit lands on the board.

(Fundamentals of Modern Manufacturing.Materials,processes and system 3rd edition, Mikell Groover, p. 847-848) 01.03

Crimping
Crimping involves the mechanical defotmation of the terminal barrel to form a permanent connection with the stripped end of a wire inserted into it.The crimping operation squeezes and closes the barrel around the bare wire.Crimping is performed by hand tools or crimping machines.The terminals are supplied either as individual pieces or on long strips that can be fed into a crimping machines.Properly accomplished, the crimped joint will have low electrical resistance and high mechanical strength.

(Fundamentals of Modern Manufacturing.Materials,processes and system 3rd edition, Mikell Groover, p. 850) 01.18