How components are assembled on PCBs? How PCBA are manufactured?

Assembly of components on a PCBs (Printed Circuit Board) is a complex process. A PCB passes through a so many types of process and machines to complete this process successfully. Main thing which is mainly important during PCB assembly is their safety i.e. ESD (Electro Static Discharge) safety.

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ESD means transfer of static charge (Electricity) when two bodies come in contact with each other. ESD is a very important factor for those companies which works in the field of electronics. ESD directly and indirectly effect the productivity of a electronics or a semiconductor based company.For ESD safety wrist-band,ESD apron and ESD slippers are used by operators.

Now we will talk step by step about the assembly process of PCB.

First, we will talk about the BOM (Bill Of Material).

BOM – It is a type of document which tells us about the components/material required during assembly for a specific board. It shows, how many types of components and what will be the quantity of each component required in assembly of a single PCB.

We can also detect that which component will place at which location of PCB.

Mainly below steps are follows for PCB assembly- 

Ø Material verification

Ø Component assembly

Ø Visual inspection

Ø Testing

Ø Packing

Material verification-

Before material verification we will discuss about the types of materials used in a PCB assembly. we can classify material/components in 4 parts-

Ø PCB

Ø SMD(Surface Mount Devices) Components

Ø Through-hole components

Ø Assembly components/items

PCB – PCB is the main component in manufacturing of PCBA(Printed circuit Board Assembly). It is the base for the assembly of all components. It may be single layer or multilayer.

SMD Components – Those components are mounted on the surface of the components are called SMD components.

Most of the SMD components are smaller in size. Due to smaller package size of SMD components, they assembled first on PCBs and their advantage is that it decreases the size and weight of our PCBA, but we face complexity during their rework due to their small package size.

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Through-hole components- Those electronic components have leads and they are assembled on PCBs by passing their leads through hole are called through-hole components. Through-hole components are bigger in size than SMD components due to this they are heavier and occupy more space.

Assembly components- In an electronic device, there is some components those are not a part of electronic circuit (no electricity flow through them) but they play an important role in board safety and their protection. For example- Heat sink, screw and Housing to cover PCBA.

All the materials are verified with the help of BOM and then send for assembly process.

 

Components assembly- As we discuss above that SMD components are assembled first due to smaller in size. Before assembly machines are programmed as per requirement. First solder paste printing is performed with the help of solder paste printing machine. After solder paste printing, components are placed as per defined locations with the help of pick & place machine. After that PCB with assembled components passes through SMT reflow oven. State of solder paste used during paste printing was in semi-solid. So the connection between PCB and component is very weak.

When PCB passes through SMT reflow oven, semi-solid solder paste converts into a solid material and makes a strong bond between PCB and component.

           After assembly of SMD components, through-hole components are soldered on PCB. Soldering of through hole components are done by wave soldering machine or sometimes manually. After soldering extra leads of components removed with the help of cutter.

          After that few supporting components are assembled such as heat-sink, Housing cover etc.

 

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Visual inspection-

                                 After assembly of all components, all components visually inspected. Due to smaller size of  SMD components, it is difficult to inspect manually. So, SMD components are verified with the help of machine called AOI(Automated Optical Inspection) before assembly of through-hole components.

Testing-

               Now after assembly and visual inspection, product is ready for testing. Testing of any product is a very critical process and direct related to the quality and durability of the product. Test procedure of any product depends on the product. A few types of tests listed below-

Ø Power on test

Ø In-circuit Testing

Ø Functional testing

Ø Burn-in testing

Ø Environmental Stress Testing etc.

All the test results recorded for quality control and for future reference. In this way a PCBA are assembled mainly.

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Packing-  After testing of product, product packed by using packing material. All electronics items are can’t be packed with same types of packing material because few of them are highly sensitive against the moisture, so they are packed with moisture free packing/moisture protective packing.

Packing of a product is an important factor for product safety as well as product marketing also. Packing create interaction between customer and the product. Packing provide essential information about the product safety, increase brand image and so many things related to product.