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Surface Mount PCB Assembly Services

Posted:03:07 PM April 12, 2021 writer: nextpcb

 

Introduction

 


Inside almost all electronic device there is a Printed Circuit Board (PCB) fitted inside. There are a number of smaller devices/components on the surface of the board, Usually the most common method is to use “Thru-hole technology method” in which components would be connected to the board via wire leads. That method is not applicable for small sized devices in which multiple components have to be fitted on the board. 
Since this method was not applicable for small devices so a new method called “Surface Mount Technology method ” was invented, in which instead of using wire leads, the components are directly mounted on the surface of the boards. It is now the most effective and commonly used method in PCB manufacturing. 
Due the several beneficial features offered by Surface Mount (SMT) PCBs they have gained immense popularity in the recent years. These PCBs are compact in size, and they also ideally meet the growing demand for smaller electronics. 

 


 
 

What is Surface Mount Technology (SMT) 


As we mentioned before Surface Mount Technology(SMT) allows us to directly mount components onto the printed circuit board (PCB). Surface-mount devices (SMD) are the components which can be directly mounted onto the PCB. SMT is now more widely used and is more beneficial unlike thru-hole technology, but both technologies can also be used simultaneous on the same board. There are certain devices such as heatsinked power semiconductors and large transformers that are not suitable for surface mounting, and so are connected using thru-hole technology. 
 

 

SMT Process 


The general SMT assembly process includes:

  • Stencil preparation
  • Solder paste printing
  • Reflow soldering
  • Reflow soldering and inspection.
  • Surface mount components (SMC) placement. 

Stencil preparation 


Basically, a stencil is a sheet of stainless steel with cuttings. The cuttings are used as specifications where solder paste should be putted and aligned with the components on the PCB. The amount of solder paste used should also be carefully calculated. 

 

Solder Paste Printing 


Solder paste is applied to one end of the stencil once it is set and squeezed using a squeegee. Once the solder paste is deposited the stencils is removed. Temperature controlled rooms are required for the boards, after solder paste is applied components needs to be moved until  placement sets in. 

 

 

 

SMC Placement 


Surface mount components (SMC) are picked hp and placed via a pick-and-place machine. On the production line assembly kits are added to the machines (pick-a-place machines).These machines are programmed and designed to pick & place the components on to the PCB at a designated area. This process is usually automated but can also be done manually, although with lesser precision. 

 

Reflow Soldering 


Reflow soldering, in this method a soldering machine is used the PCB boards along with solder paster and components are passed through it. PCB board is passed through the machine which 
provides controlled heating which melts the solder and solidify which in turn makes solid solder joints. The temperature must be carefully regulated so the board, so it is not poorly soldered. 

Inspection 


The final step is to inspect the PCB. After all the processes are done the PCB board is then cleaned and inspected to identify and faults or flows which may cause potential problems, if any problems are found they are then repaired or reworked on.  


 

Advantages of Surface Mount Technology 


There are a number of advantages of SMT which make it the go-to method for PCB manufacturing and assembly. 

  • Lower costs due to efficiency in process and simplified production line. 
  • SMT enables lower resistance and inductance at the connection, mitigating the undesired effects of RF signals providing better high frequency performance 
  •  SMT enables higher circuit speeds since PCBs created with the SMT process is more compact. 
  •  SMT components allow for higher density of connections as there is more space for routing which would otherwise be occupied by holes. 
  •  The biggest advantage of SMT is the ability to incorporate smaller sized components, most of the components used can be reduced by 60-70% in size, volume, and weight. 
  • The entire process is automated as opposed to THT where some parts may need to be inserted manually. SMT parts can be installed on circuits using an automated pick-andplace machine.  
  • Components used in SMT are more commonly available due to their large demand and are usually cheaper as opposed to through-hole components. 

Advantages of SMT based on design  

  • Significant reduction in weight 
  • Optimal utilization of board space 
  • Considerable electrical noise reduction. 

Advantages of SMT based on manufacturing

  • Reduced board costs.
  • Minimized material handling costs.
  • Controlled manufacturing process. 
Tag: PCB assembly pcb assembly PCB Assembly
  • PCB
    Prototype
  • PCB
    Assembly
  • SMD
    Stencil

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