(Surface Mounted Technology) is the surface assembly technology (surface
mount technology), is currently the most popular electronic assembly
industry, a technology and technology。 Smt What are the
characteristics: high assembly density, electronic products, small size,
light weight, the size and weight of the chip components only
traditional packaging components around 1/10, the general use of smt,
the electronic product volume reduced by 40% to 60% Weight reduction by 60% to 80%. High
frequency characteristics, reducing the electromagnetic and radio
frequency interference, high reliability, anti-vibration ability。 Low defect rate, easy to achieve automation, improve production efficiency。 Reduce the cost of 30% to 50%。 Saving materials, energy, equipment, manpower, time and so on.
2、Smt basic process elements: printing (or dispensing) -> placement -> (curing) -> reflow soldering -> cleaning -> detection -> repair. So in summary of the smt workshop as a dust-free workshop on the whole to meet the needs of the production process, and production equipment, production environment is closely related.
3、The main advantages: 1, to prevent dust, the air has a lot of floating dust. 2, to prevent body hair and other hair fell to the product, the strict need to bring gloves, so as to ensure product quality. 3, to prevent static electricity.
4、What are the SMT shop constructions?
SMT on the environment cleanliness, humidity and temperature have certain requirements, in order to ensure the normal operation of equipment and assembly quality, the following requirements for the working environment.
supply: power supply voltage and power requirements in line with
equipment requirements: voltage to be stable, China requires
single-phase AC220V (220 ± 10%, 50 / 60HZ), three-phase AC380V (220 ±
10%, 50 / 60HZ) To the requirements, the need to configure
the power supply, power supply power is greater than twice the power
consumption of the device. Some areas of the
voltage is very unstable, the equipment will have an impact, so in
particular the need for regulator or transformer configuration, or
equipment prone to damage due to fluctuations in power supply。 This is often not too much attention. In
addition, if the device rated voltage and installation of the use of
the environment does not match the voltage, also need to configure the
2. Environment: (1) temperature As the printing workplace ambient temperature requirements of 23 ± 3 ℃ for the best, so the plant's best ambient temperature for this setting. Usually the factory temperature is generally set to 17 ~ 28 ℃; if not, can not exceed the limit temperature of 15 ~ 35 ℃。 (2) humidity The humidity inside the plant has a great impact on product quality. Humidity is too high, easy to moisture absorption components, the moisture sensitive components unfavorable, while the solder paste exposed to humid air is also easy to absorb moisture, resulting in welding defects. Humidity is too low, air dry, prone to static electricity, electrostatic sensitive (ESD) components unfavorable。 So the humidity must be controlled on the factory。 General requirements within the plant relative humidity of 45% to 70% RH or so, and some provisions of 30% to 55% RH, loose some of the 40% to 80% RH. (3) air cleanliness workshop If the gray layer is very large, for small components, such as 0201,01005 and fine pitch (0。3mm) components of the placement and welding quality impact, while increasing equipment wear and even equipment failure, increase equipment Maintenance and repair work.
production workshop in addition to dust in the air, there are still
some chemical gases, if these chemical gases are toxic and harmful, then
the human body will cause harm; if the gas is corrosive, serious will
affect the reliability of the product. So the workplace to keep clean, dust-free, non-corrosive, no smell gas。 To ensure the quality of welding products, the normal operation of equipment and human health. Workshop air cleanliness of the best up to 100,000 (BGJ73-84). In
the air-conditioned environment, there must be a certain amount of
fresh air, as far as possible to control the CO2 content below 1000PPM,
CO content control in 10PPM the following, to ensure human health。 To ensure that the factory cleanliness of 100,000, must pay a considerable cost, the general factory is difficult to do. To ensure that such an environment, personnel must enter the factory vacuum, the entire plant has negative pressure。 In
the competitive environment of the market, production profits are
getting smaller and smaller. If such requirements are not met, the
cleanliness must be stipulated. For example, the cartons that affect the
dust clearly indicate that they can not enter the SMT workshop. Dust
caused a typical case of equipment failure: a placement device, boot
phenomenon is garbled on the screen, at first thought that the operator
accidentally changed the machine data or software misuse, then there is
suspected battery problems, because the machine has been running well , And later check found that the computer inside a lot of dust, clean the machine after the failure to eliminate.
3. Plant construction: (1) floor load If the equipment is not placed on the first floor, the load on the floor have certain requirements, that is, the floor load must be greater than or equal to 500kgf / m2, the equipment can be placed, otherwise there will be dangerous. (2) anti-static As the current production site must have a good anti-static measures, production equipment must be well grounded, should be used three-phase five-wire grounding method and independent grounding. Production site floor, table mats and chairs, etc. should meet the anti-static requirements. Specific ① personnel wristbands; ②EOS protective container; ③EOS protective desktop; ④EOS protective floor and mat; ⑤ building ground; ⑥ public ground; ⑦ ground. (3) exhaust reflow and wave soldering equipment have exhaust requirements to ensure adequate suction capacity。 In addition to flue gas ventilation, but also must have enough exhaust flow, such as 200m2 / h, to ensure that the wind out。 In addition, but also to maintain a certain static pressure, such as 100Pa, the other exhaust pipe diameter also has certain requirements. (4) lighting plant should have good lighting conditions, the ideal illumination for the 800LUX × 1200LUX at least not less than 300LUX is a visual inspection of the local must ensure that lighting requirements. (5) vibration of the equipment to consider the impact of vibration will affect the accuracy of precision equipment such as placement machine, while the placement machine vibration will also affect the other equipment and construction, it should be on the environmental vibration have certain requirements, taking into account the equipment on the environment Impact. Equipment is best placed on the first floor, if necessary, take some anti-vibration measures.