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Surface-mount engineering (SMT) is really a system to mount elements straight onto the surface of printed circuit boards. An electronic gadget so made is named a surface-mount gadget (SMD). Inside the business it's largely replaced the through-hole engineering building approach to fitting parts with wire prospects into holes from the circuit board. An SMT element is usually smaller sized than its through-hole counterpart since it has both smaller leads or no leads whatsoever. It may have short pins or prospects of many styles, flat contacts, a matrix of solder balls (BGAs), or terminations around the physique on the element. Extra and much more engineers want to chose SMD components as opposed to DIP elements, but SMT products is so huge and high-priced. Wonderful PCB propose a much superior method for engineers who choose to SMD himself but don?It wish to pay as well a lot for SMT machine. We termed it semi-automatically Surface mount. Wonderful PCB suggest purchaser to accomplish as following processes,
1. Get solder paste. Solder paste 500g imported 1 close to USD one hundred, Solder paste 500g manufactured in China close to USD 80. Two varieties of solder paste, Tin lead and leadfree. Leadfree is close to USD 20 per 500g higher than Tin lead. The solder paste ought to be stored in 0-10 C affliction.
2. Make the stencil in accordance for the PCB gerber( pads required hollow out). Serval types of size of stencil. Standard size is 370mm*470mm,420mm*520mm,470mm*570mm. Nomral thickness of stencil is 0.13mm. it have to be with fiducial marks half etched or hollow out. Fiducial marks size usually is dia. one.5mm.
3. Correct the stencil around the machine as pic one exhibits.
4. Resolve the PCB around the machine. Commonly PCB should really have borders at the very least 5mm at two sides with tooling holes . Then PCB could possibly be correct steadily on the machine. Tooling holes dimension ordinarily is three.2mm.
five.?Put stencil about the PCB?
6. Print solder paste within the stencil, then when you lift up the stencil, PCB are with solder paste.
7.Put the parts about the solder paste on PCB.
8. Place the PCB board  with solder paste and elements?to reflow Oven. Reflow Oven temperature is about 225-240mm for tin lead solder paste and 250mm for lead totally free solder paste. the solder paste will melt and assemble the components.


 

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