Printed Circuit Board Manufacturing

By Akber Roy - Chief Technical Officer at RUSH PCB

Into one side of the manufacturing process goes the design and materials for a project, and depending on the desire of the designer, out the other side of the process is the complete fabricated Printed Circuit Board (PCB)/Assembled Printed Circuit Board, (PCBA)/Finished-product (Box Build).
Between the input and output of the process, the manufacturer is:
  • Using software to check the design for manufacturability (DFM)
  • Fabricating the printed circuit boards
  • Ordering and assembling the components onto the PCBs
  • Possibly wiring and installing the PCBs into the final box assembly

Many manufacturers provide the following services:
  • Quick Turnaround production of printed circuit board fabrication and assembly
  • Prototype and very small run PCB manufacturing
  • Small and medium production runs of PCBs
  • Turnkey assembly
  • Lead-based or lead-free solder

Circuit Design

A company designing electronic equipment may not be the company manufacturing the equipment. Quite often, because of the huge investment in the equipment needed for manufacturing, one company designs and sells an electronic device while using another company to manufacture part or all of the device.
Between the designer and manufacturer, when they are different companies, even at the early stages of development, communication is very important. If some part of the design doesn’t work with the manufacturer, half way through production is a bad time to discover this. Early in the development of a product, detailed discussion with the manufacturer can save a lot of money.

Design for Manufacturing -- DFM

This is software manufactures use once they receive the PCB design files (Gerber Files).
The manufacturer uses this software to make sure the Gerber files meet all the manufacturing requirements.
Some of the things the DFM looks at are:
  • Trace width
  • Guard space between traces
  • Conducting pads around the holes
  • Smallest hole size
  • etc.

The DFM software analyzes and refines the design to:
  • Adjust for the dimension changes that occur during the manufacturing process
  • Optimize cost
  • Check signal integrity
  • Increase yield and reliability

Fabrication of the Printed Circuit Board

Using conductive tracks, solder pads, and other features etched from copper sheets laid out on insulating material, a printed circuit board (PCB) mechanically supports and electrically connects electronic components.
There are three major types of printed circuit boards: single sided, double sided, and multi-layered. Variations on each of these are:
  • Rigid PCBs
  • Flexible PCBs
  • Rigid and Flexible PCBs
  • Metal Core PCBs
  • Mil Spec PCBs
  • Lead Free PCBs (RoHS Compliant)
  • High Density Interconnect PCBs
  • Heavy Copper PCBs

PCB Assembly

Printed circuit board assembly is the placing of the components onto the printed circuit board. This assembling includes all surface mount devices, through-the-hole devices, BGA/CGA devices, connectors, and hand soldered devices.
For surface-mount and through-the-hole components, high speed machines are used to precisely place the components onto the PCB.
Once placed, the components are permanently attached using wave soldering or reflow soldering techniques.

Box Build – Producing a Finished Electronic Package

Populated with all their parts and connectors, finished PCBs still aren’t ready for the end user. The designer might not be willing or have the capability of building the PCBs into the final box. In this case, as part of the process, the manufacturer will wire the PCBs into the finished boxes. This is called Box Build.

Turnkey Assembly

Turnkey assembly is where the manufacturer fabricates the PCB, purchases the specified parts, assembles the PCB, and builds the box with the PCB wired inside. in other words, the manufacturer provides completed equipment and, to use it, all that needs to be done is to turn it on (turn the key).

Lead Based versus Lead Free Solder

The use of lead based solder is something that needs consideration.
Used on printed circuit boards, lead based solder generally flows more easily and bonds in the solder joints at a lower temperature than lead free solder, but there are drawbacks to using lead based solder.
When the electrical and electronic equipment is no longer useful, lead based soldered equipment can’t be just thrown into a landfill, it has to be recycled. Lead is a toxin to human and animal life, and when no longer used, equipment built with lead based solder is considered toxic waste.
Some countries have outright banned the use of lead based solder.

Quality Control

Quality Control – this is inspection and testing to make sure the boards are assembled and manufactured correctly. To reduce human errors from repetitive inspection, automatic inspection methods are used.

Electrical Testing

Checking continuity to make sure wire traces go through and there are no hidden shorts on printed circuit boards, automatic probes are used .

Automated Optical Inspection (AOI)

Automated Optical Inspection equipment is used to detect flaws, failed solder joints, incomplete etching or over etching, improper vias, improper drilling, component misplacement, wrong components, etc.

X-Ray Inspection

In order to see how well the solder joints were made, Ball Grid Array components (BGAs), Micro-BGAs, Chip-Scale Packages (CSPs), Flip Chips and other hidden connection components require X-ray equipment.

Quick Turnaround Manufacturing

With Quick Turn Manufacturing – some situations will be quicker than others.
  • Transportation -- overseas manufactures ship greater distances and the shipping will take longer
  • Complexity -– no matter how quickly products are needed, more complicated boards take more time to manufacture
  • Parts availability –- specialty parts may not be available right away, or have to be transported great distances, which increases the time of manufacture
  • Process Time –- if the manufacturer has to fabricate the circuit board, order the parts, and then assemble the parts onto the board, the whole process will take longer to turn around than when the manufacturer just assembles customer provided PCBs and parts

Short Run and Prototype Manufacturing

Depending on the manufacturer, a short run can be 1 to 5, 1 to 20, or 1 to 40 boards or systems.
The per-board cost for short runs is higher because the time to set up the manufacturing run is spread out among fewer boards.
Since a prototype PCB is an experiment to see if a design works, the only real difference between a prototype PCB and a short run PCB is a prototype can skip steps like the silk screening of part numbers onto the board.

Contact RUSH PCB

For further information about manufacturing, contact the engineers at RUSH PCB  .