JLCPCB is the best PCB assembly manufacturer in China, who provides free assembly for Your PCB.SMT ( Surface-mount technology )is the process of mounting and fixing electrical components on PCBs.
PCB prototype only $2 ,and assemble them from $0 .
Jlcpcb’s highly professional staff and cutting edge machinery can effectively lead customers to higher results especially through the faster PCB production and SMT Assembly services. 
- The PCB assembly of SMT and THT could be executed simultaneously on the same circuit board but this service is way more efficient as soon as it is oriented to SMT since this technology provides more accuracy and reliable components assembly.
Properties of SMT:
- SMT processing and its products are highly efficient and reliable as it shows a high-frequency ratio under EMI and reduced RF interference.
- Ensured and safe execution of SMT products and their assembly can be judged through a low reject ratio and extended capability for vibration resistance and damage repair.
- Mounting accuracy attained through SMT assembly is way better than THT. The process carried out through automated machinery and multiple testing makes PCB components more accurate and reliable.
- SMT allows a wide range of miniature products that turn out to be more functional. SMCs (surface mount components) and SMDs (surface mount devices) manufactured through SMT are 40-60% smaller and 60-80% lighter weight and accurately soldered on PCB.
Machinery and material used for SMT:
Contents
- Stencil printer- Solder stencil printers are used to place solder paste accurately on the electric board.
- Pick and place machine- PNP is an automated robotic machine that picks the component through the vacuum, rotating it in the right orientation as it is programmed, then it places the component on the board.
- Solder paste- It is used for soldering to establish physical connection of the components on the circuit board. Different elements are used as solder paste such as Sn, Pb, Ag, and Sn-Pb IMC for strength and efficient fixing.
Soldering a circuit board
- Adhesive- It is used to fix components in their place so that components won’t fall off or detach.
- Flux- Acid and resin flux is used to wet the surface and clean it from dirt and oxides to eliminate unnecessary chemical reactions and purification on the board.
- Cleaning agent- Special agent or cleaning is used to clean the surface and residues deposited on it after soldering.
SMT assembly process in JLCPCB’s factory:
- Check of material:
Firstly , Check the PCBs and electronic components, ensure that they meet the relevant requirements and prepare the SMC and PCB, and test them to see if they have any faults.
- Stencil formulation:
To deposit solder paste, stencil is used to maintain its fixed layout. It is formulated according to the solder pads for the layout of PCB. A stencil printer is used to run this function. Various steel stencils are used based on the board design.
- Printing of solder paste on PCB:
Gold pleated solder pads of PCB then connected to select SMCs through solder paste. It is a mixture of tin and flux. Squeegee and silk-screening methods are used to apply solder paste with stencil on the PCB.
4. Components positioning:
Once the printed PCB has been confirmed to have the correct amount of solder paste applied it moves into the next part of the manufacturing process which is component placement. Each component is picked from its packaging using either a vacuum or gripper nozzle, checked by the vision system and placed in the programed location at high speed. There is a large variety of machines available for this process and it depends greatly on the business to what type of machine is selected. jlc focus on small batch , flexibility is more important.
5. Pre-Reflow Automated Optical Inspection (AOI):
- This is a very crucial part of the construction of PCBA is that there should be some inspection is done after placing the different component since the correct placement of component infers the complete working of the PCB board.
Reflow Soldering Process
Reflow soldering is the most common method of attaching surface mount components to a circuit board. It’s a process in which a solder paste is used to temporarily attach one or several electrical components to their contact pads, after which the entire assembly is subjected to controlled heat, which melts the solder, permanently connecting the joint.
Now JLCPCB can support through-hole components by offering hand soldering services, like connectors. The part’s assembly type marked with “hand soldering” in our SMT Parts library will be assembled manually.
Cost: $3.5 hand-soldering labor fee + $0.02 manual assembly fee per joint
Build time: SMT assembly service time + 1 more day
6. Inspection and testing:
JLCPCB has some advanced types of equipment including:
- Fully-automatic LDI exposure Machines.
- Fully-automatic Solder mask Production lines.
- Fully-automatic PCB Test Machines.
- Fully-automatic CCD exposure Machines.
- Fully-automatic PCB Etching Equipments.
- Fully-automatic Screen-printing Production lines.
- Fully-automatic Electroplating lines.
https://jlcpcb.com/ele
Multiple Testing Before Shipping
First, AOI (Automated Optical Inspection)
Second, Flying Probe Testing
Third, Final Quality Checking piece by piece before shipping
JLCPCB has Smart system and powerful data center .It can help staffs to track the reason and operator easily .
Register jlc to get $27 coupons! https://jlcpcb.com/ele
Have a glance at JLCPCB’s SMT factory :
https://www.youtube.com/watch?v=NEfrUnhGMRY