PCB Assembly Standards: Ultimate Guide For Beginners

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What is the IPC standard?

PCB assembly standards stand for 'Institute for Print Circuits’ belongs to the business of electronic interconnection industries. Officially IPC provides PCB related standards and now it is also known as Electronic Industries Connectivity Consortium.

 IPC is known as an international industry with an association of more than 4000 companies engaged in the use, specification and design of PCB'S and also assemblies including, advanced microelectronics, military applications , aerospace, automotive industry, computer, industrial and medical equipment, telecommunications industry, etc.

The relevant PCB assembly standards Design PCBs, manufacturing processes, and electronic assemblies to achieve reliability, quality, high performance, and meet user specifications. This is the tree for the PCB shown below.

PCB assembly standards

 Printed Circuit Standards Institute for PCB

These are the requirements for PCB related products to ensure safety, reliability and high performance. Quality, attention and commitment need to be maintained throughout the entire manufacturing process.

 To meet user/customer specifications and expectations, many PCB manufacturing industries use these standards to maintain consistency, high reliability, quality and commitment. These also help to improve the manufacturing process of PCB products in many ways. The IPC standards in the PCB manufacturing process require

Control the end products with high quality and high reliability.

  • Improved communication with multiple employees and suppliers
  • Cut the cost
  • Raise your reputation and a new opportunity

To work with these standards for PCBs, users are required to know the terminology provided by IPC, thereby helping to communicate and purchase its standards. The provisions in the IPC standard include.

PCB assembly

5 PCB assembly standards

Acceptance testing: It is required to check if the product is accepted or not, it depends on the user or the buyer or the supplier.

Assembly, assembly: Consists of joining or assembling different parts and joining together.

Resistance: it acts as a coating material to protect the product during manufacturing and testing for plating, corrosion and welding, etc.

IC (Integrated Circuit): variety of electrical circuits connected together in one place by a single material to perform the desired function based on the application.

Flexible strength: Refers to the tensile strength of the fiber by the material that can be bent in a curve or folded or turned.

Critical Activity: Refers to the entire activity, process, and product characteristics.

IPC standards for PCB design, manufacturing and assembly are linked at every step to achieve a quality product, maintaining a competitive spirit throughout the manufacturing process. These are linked and performed in turn in each PCB design and manufacturing step to get the desired output product.

PCB assembly standards procedure

The most complete procedure is described by the following plugging procedures according to the principle of increasing height (relative to the PCB surface):

  • Attach eyelets (or asterisks, studs, studs... depending on your calling habits)
  • Jumper wire
  • Mounting components coaxial (axial)
  • Mounting radial components
  • Attaching bales of different shapes
  • Manually attach components that cannot be plugged in 
  • Wave soldering, dip soldering
  • Trim fixing pins (hand-mounted components 6.)
  • Check and adjust

Supported by CAM/CAD technology, this technology limits a lot of human errors when mounting by hand, but if the person loader is wrong, it can lead to mass errors, due to the shape of the device.

Variety of pcb assembly components

 The variety of components that the mechanical structure is complicated and difficult to adjust requires the technician to weigh and align the machine to be sensitive and experienced to perform the maintenance and repair work. .

The external shape structure of different types of components that this technology breaks down to attach to groups of external shapes that we have a plug order may be unique, this is also a difficult point of the process. This technology when it is necessary to balance productivity between machines.

Because the legs are folded and then soldered, plus the tilt of the component legs to the PCB and no need to cut the legs, this solder joint is much better, but this is also a difficult point for later repair, if not carefully enough. It is very easy to damage the solder surface and printed circuit when disassembling to replace components.

In fact, it is still necessary to cut the error correction pins, but the number of remaining pins is not much, so the debugging work is much less complicated.

PCB assembly technology is developing more and more

The functions of electronic products are more and more sophisticated, requiring smaller components, circuit boards are also denser with components, and need to be more compact, so first components no longer have legs as before (MELF Metal Electrode Leadless Face is the first transformation) to components that are only small rectangular blocks called CHIPs, people still use their hands to attach these details at first.

 Until the component is too small to be used by hand, plus the demand for high output, density as well as large quantity on a PCB that surface-gluing technology is born completely using machines and humans only play a role control machinery and equipment.

Auto-Mount or SMT Technology

In the 1960s, IBM pioneered the development of this technique for small computers to serve the US space program, due to the need to miniaturize computers on rockets to launch into space. Thus, due to the
need to shrink electrical circuits as well as to lighten the structure of electronic circuits, SMT technology was born, but SMT only became popular in the late 1980s.

Like Auto-Insert technology, SMT simulates a replacement machine arm to  paste CHIP-type components on the PCB, so it is also called SMT (Surface Mount Technology).

In fact, to do this work, many new supporting technologies have been formed, for example, at the stage of existence of both Auto - Insert and SMT, people use glue technology (dispenser) to fix the position.

CHIP on the PCB next to the component pins that have been folded in Auto - Insert technology and then soldered (solder ware) at the same time, or printed with CHIP solder paste combined with CHIP glue and combined with Auto - Insert solder with REFLOW and wave solder…etc.

The full first-stage procedures are as follows:

  • Plug the eyelet (or asterisk, rivet, rivet... depending on calling habits)
  • Jumper wire
  • Plug in components coaxial (axial)
  • Plug in asynchronous (radial) components
  • Plug in different shaped bales
  • Flip the CHIP plug with glue
  • Dispenser
  • Paste CHIP ONLY
  • Paste IC (if any)
  • Reflow (steaming glue)
  • Plugging in components that can't be plugged in
  • Wave soldering
  • Corrective leg cutting
  • Check and adjust

When the technology of miniaturization of components reached today, people almost completely eliminated plugging through holes and glued the CHIP with glue, the process remained as follows:

  • Print solder paste
  • Paste CHIP ONLY
  • Paste IC
  • Reflow
  • Flip the other side over and repeat the procedure as follows:
    • Paste CHIP ONLY
    • Paste IC
    • Reflow
    • Hand solder non-glued components (maybe some through-hole components)

    The weak point of this case is that the first reflow can cause an error for the back gluing and the next reflow will affect the solder joint of the previous reflow.

    So now SMT plug technology can do printing and gluing on both sides and reflow only once.

    With each combination of technologies, there is always an appropriate process, and when combined with specific materials, tools, and supporting machinery, the organization of production requires experience, the acumen of the technical person.

     It gives rise to different actual processes that make products of a high standard for companies, for example to produce a flexible board one has to combine different jig mount for support because (say) SMT machine can only plug in a 1.6mm thick, rigid regular PCB while the soft board has a thickness of 0.09mm (super thin) and flexible (foldable) 

    Print solder paste
    • Limitation in PCB assembly Process

      The smaller the component, the more it has reached the limit that the printing of solder paste can hardly meet the quality and technology is difficult to control, so now some manufacturers of plugging devices have released devices gluing components onto the PCB with FLUX is an adhesive.

      Solder has been prepared on the poles or pins of the component, and then the device sucks the solder paste into the FLUX (flux as an adhesive) and then pastes it on the PCB for reflow, solder on the pin.

      • Solder paste solder on the copper PCB circuit

        In the current state of low technology development, in order to produce a wide range of products at low cost, in fact many companies still apply combine both Auto-Insert and Auto-Insert with SMT glue, or AI with both SMT Glue and SMT solder paste, can also be AI with SMT solder paste, then the process will change SMT before AI after.

        Foreign companies with a lot of capital, quality needs and the policy of using few employees should make modern investments to apply modern SMT technology than most of them just use SMT with solder paste.

        Summary

        To understand and be able to grasp the current work, as well as take shortcuts or learn, learn and add to themselves how to produce electronic circuits on PCBs in factories, technical workers Technicians, engineers, and technicians who want to understand this technology should learn about all the processes that currently exist in the production of electronic products.

        In addition, this document also helps production and quality managers to understand the process of adding technology to contribute to improving production and quality management.

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