Consigned PCB Assembly Medical PCB
1. The insertion and installation of electronic components shall be neat, beautiful and stable.At the same time, it should be convenient for welding and conducive to heat dissipation during the welding of components.
1.1 components are classified into resistance, capacitance, diode, audion, transformer, plug-in line, seat, conductor and fastener according to the circuit diagram or list.
1.2 pin shaping of components
1.2.1 basic requirements for component shaping.The pins of all components shall not be bent from root, generally should be kept more than 1.5mm.Try to place the component surfaces with characters in an easily observable position.
1.2.2 pin shaping and manual shaping for components. The bent pin can be shaped by tweezers or small screwdriver.
1.3 manual insertion of components are in order, plug-ins should meet the process requirements. Do not touch the pins of components and the copper foil on the board.
1.4 the inserted mode, diodes, capacitors, resistors and other components are installed on the printed PCB board in a prone position.
2. main soldering tools, manual welding is a technology that every electronic assembler must master. Proper selection of welding materials and flux, select welding tools according to actual conditions are the necessary conditions to guarantee welding quality.
2.1 solder and flux
2.1.1 the solder can fuse two or more metals into a whole fusible metal or alloy.Tin is 62.7% and lead is 37.3% in common.The ratio of solder melting point and freezing point is 183 ℃, can directly cooled to solid from liquid, without half liquid solder can rapidly solidified, shorten the soldering time, reduce virtual welding,the point temperature is called the eutectic point, the composition ratio of solder called eutectic solder.Eutectic solder with low melting point, melting point and solidification point consistent, good fluidity, low surface tension, good wettability, high mechanical strength, solder can withstand greater tension and shear, good electrical properties.
2.1.2 flux is a kind of welding auxiliary material, whose functions are as follows: 1. Remove oxide film.2 prevents oxidation.3 reduce surface tension.Make the welding spot beautiful.The commonly used flux is rosin, rosin alcohol flux, solder paste, zinc chloride flux, ammonium chloride flux and so on. Soldering often use with rosin flux, 39 tin lead solder wire containing 61% tin, also known as rosin solder wire.
2.2 selection of welding tools
2.2.1 ordinary electric soldering iron is only suitable for occasions where welding requirements are not high. Such as welding lead, connecting line, etc.