What’s Inside a PCB Manufacturing Facility? A Tour of Royal Flex Circuits

February 09, 2019 by Mark Hughes

Take a look inside a PCB manufacturing facility.

Take a look inside a PCB manufacturing facility and gain some insights about how boards are professionally fabricated.

Royal Flex Circuits is a PCB manufacturing facility in Santa Fe Springs, California. The company is part of the Royal Circuits Group owned by Royal Circuit Solutions and focuses on flex and rigid-flex circuit boards, particularly quick-turn PCB manufacturing for both enterprise-level and single board fabrication.

AAC’s Technical Editor, Mark Hughes, was invited to tour a new facility in progress. Royal Flex Circuits had outgrown its previous space and, at the time of the tour, was in the process of moving into a new one.


Some of the Royal Circuits team by the wet-process spill containment area. Pictured from left to right: Scott Khono, Omar Madrigal, Larry Ybarra, Tracy Ho, Riki Gracia, Mihir Shah, and Bob Meyer. All images property of Mark Hughes.


So what equipment is in a PCB manufacturing facility? Here's a look at parts of the process of PCB fabrication.

Single Spindle DLG

The LENZ single speed DLG performs micro drilling and routing of PCBs. To maintain accuracy over wide temperatures and humidity conditions, the machine is built atop blocks of precision-ground granite. An automatic spindle drills holes and sensors can detect broken drills.


Royal Circuits employee Danny Ho in front of the LENZ drilling machine

UV Laser Microvia Drill

Microvias are drilled with lasers to reach precise depths. Shown below is the ESI UV laser microvia drill. Since the power output of lasers decreases over time, employees have to carefully document and adjust the machine for each cycle and process.


ESI’s UV Laser microvia drill machine.

Computer Vision and Manual Inspection

As you can imagine, creating a working PCB requires careful inspection and quality control during each stage of the manufacturing process. Manufacturers inspect with a variety of machines at all stages of the process.

Automated inspection machines use computer vision and conductive probes to ensure that there are no electrical or mechanical flaws that might prevent a PCB from working. Humans inspect the PCBs to look for flaws that automated machines cannot detect.

Flying Probe Machine

A flying probe machine takes two conductive probes and touches various pads in different locations on each PCB. Electrical conductivity indicates that the pads are connected and the net is electrically sound.


A flying probe machine tests continuity between nets by rapidly moving probes around a PCB (image manipulated to blur patterns)

More Machine Vision and Human Inspection

Automated machine vision cameras methodically look for flaws in PCBs. Each potential error has to be manually inspected by a trained technician who then accepts or rejects the potential flaw. A Camtek inspection camera below looks for flaws that might occur during the manufacturing process.

When a potential error is detected, a technician will determine its importance and then manually repair the PCB, if possible.


A technician manually inspects a PCB for errors.

PCB Sampling

Not all PCB testing is non-destructive. Each PCB has a small area of the board that is sliced away to determine the quality of plating after a via-plating bath. Other parts of the PCB are encapsulated in epoxy and viewed via a special microscope that inspects quality and thickness.

Each board is tested to determine the quality of plating. A part of each board is sacrificed for testing.


Portions of boards are encased in epoxy for separate forms of testing

Impedance Coupons

For very high-speed circuits, a consistent impedance is essential. Something as seemingly insignificant as the varying amount of epoxy in between layers of a PCB can change the impedance by several percent—enough to cause signal integrity issues.

To confirm the actual impedance of a PCB, an impedance coupon is added to the edge of every PCB. 


An example impedance coupon attached to some boards


Impedance coupons are added to the perimeter of each board that has a controlled-impedance specification. Technicians can then measure the impedance of the coupon to determine the impedance of the board.


The full transition of the shop from the old facility to the new facility is not quite complete—the wet-process area is still under construction, so I plan to visit again. But I certainly enjoyed watching the various stages of construction.

Thank you to the owners and workers at Royal Flex Circuits for their willingness to show me around the shop.


More of the Royal Circuits team!