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SMD Manufacturing
How is it possible that our product can be made for such a low price?
There are a number of factors that play a major role. One of them is efficiency and a high level of production automation. Everything a machine can do saves human labor. The application of SMT has several major advantages. The components used are small, often even tiny. This allows electronics to fit onto a smaller and cheaper printed circuit board (PCB). Also the enclosure can be smaller and cheaper. However the most important cost saving is caused by automatic assembly with SMD components by a pick and place machine. A pick and place machine works fast (10,000 or more components per hour) and very accurate (better than 0.01 mm precision). It is fully automatic, with minimum labor. An enormous cost saving can be achieved through Surface Mount Technology by raising the production level per human working hour. An extra advantage of SMT is that the weight of the components is much less and the leads are much shorter as compared to through-hole components. So less mass and shorter "arm of the force" which results in less torque on the leads during vibration. The vibration resistance increases significantly.
What are SMD and SMT anyway?
SMT stands for "Surface Mount Technology". SMT is the name of the mounting technique. It uses components with leads that are placed on the PCB instead of through the PCB. When the leads go through the PCB we call it "through-hole".
SMD stands for "Surface Mount Device". SMD is the name of the component, suited for SMT.
In practice everybody talks about SMD, being the technique or the component.
SMT Production Steps
- Screening - Solder paste is applied on the contact pads using screen printing.
- SMD mounting - The pick and place machine picks up components from various feeders and places them on the correct position on the PCB. The leads are pressed slightly in the solder paste. As the solder paste is a bit sticky, the components stay in position while the other components are placed.
- SMD mounting by hand - Some components can't be handled by the pick and place machine. Those are placed manually.
- Reflow soldering - The PCB is passed through an oven so the solder paste melts and actually solders the components to the PCB.
- Inspection - The soldered PCB's are optically inspected for correct mounting and soldering. After that the PCB is ready for the nest step: through-hole mounting.
- Testing - As a step in between, the PCB can be electrically tested. Any irregularities can be corrected before the through-hole components are mounted. Almost all of our products contain an absolute minimum of through-hole components. So the PCB is tested once when the PCB is completely assembled.
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Through-Hole Manufacturing
Another name for "through hole" components is "conventional" components. These components are mounted manually. Automated machines do exist (sequencers) but these are very costly.
Our Thru-Hole operation is backed by high-end technology to deliver greater efficiency and exceptional quality control. Mechanical sequencing places Thru-Hole axial components in the order they will be assembled. Thru-Hole assembly automation with a Component Locator ensures proper placement for each piece.
Manual mounting is expensive, why do that anyway?
In some cases there is no alternative for a through-hole component. When the size is too large, when mechanical stress is too high or when power dissipation is too much. With some components the SMD type can be bought only in reels of at least 1,000 pieces, while all you need is 100 pieces. In those situations through hole components are selected.
Through-Hole Production Steps
- Bending and cutting - The preparation for production means bending the lead to the correct pitch (hole distance) and cutting the leads to the appropriate length. Most components are delivered on paper tape that can be handled by a cutting and bending machine.
- Mounting - All components are manually placed in the PCB. The leads are fit into the holes and extend about one millimeter.
- Wave soldering - The PCB with all components positioned is placed on the wave soldering machine. Flux is foamed to the bottom of the PCB in order to clean the contacts and improve the quality of the solder joints. Next the PCB and the components are heated to 100°C. During the heating the flux will clean the contacts by etching and also a thermal shock is prevented. Now the PCB is transported over the solder wave. Liquid solder is pumped against the bottom of the PCB. Because of the turbulence in the liquid solder the contacts are well wetted and the solder fills the gaps between the holes and the leads. The result is a strong and reliable joint.
- Inspection - The joints are optically inspected for correct soldering. The PCB is now ready to be tested.
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Mixed Technology Assembly
This Manufacturing process inter-mixes SMT and TH technology components. Marktech can provide the following Mixed Technology combinations.
- SMT & T-H
- Top SMT & Bottom T-H
- Top SMT & T-H & Bottom SMT
- Top SMT & T-H & Bottom SMT & T-H
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Chip on Board Assembly
On electronic designs, Chip-On-Board (COB) allows more functions to put in the same amount of space to achieve miniaturization of volume and weight.
Other Benefits of COB
- Lower cost
- Flexie layout - Number of wire bond or PCB layout can be effortlessly changed to meet your requirements.
- Shorter production period. Only one third of standard IC package.
- Shorter signal interconnections for improved signal performance.
- Good reliability: Can withstand thermal shock test, Pulse test, and mechanical test of at least 27kg load.
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