Printed Circuit Boards (PCBs) have gained traction since they became adoptable for producing different kinds of consumer electronics. Today, you can use the circuit boards in making microphones.
This article is an expose to what the microphone PCB is all about. We also talk about the types of microphone PCBs and how you can maximize the usages.
The Definition of Microphone PCB
This can be loosely translated to mean a circuit board dedicated for use with microphones. On its part, a microphone is an instrument (a transducer), which converts sound waves into an electrical signal/energy. The conversion into electrical signal can come in the following variations:
- Amplifying the signals as an analog signal.
- Making a digital conversion of the electric signal into a signal that digital audio devices like computers can process.
How Does a Microphone PCB Work?
The simplest definition is that this has to do with the combination of the microphone with a Printed Circuit Board (PCB).
Thus, the microphone circuit board is a Printed Circuit Board (PCB) that has an electret microphone embedded on it.
With the PCB serving as the architectural backplate of the microphone, it aids the reduction of the numbers of electronic components needed for the microphone’s construction. Instead of adding the individual components to the microphone, those are instead added to the PCB.
The Types of Microphone PCB
Today, you can see different kinds of microphones in use. They are also deployed for use in different applications, such as motion picture production, hearing aids, telephones, megaphones, public address systems and sound recording.
These microphones are also used for the following purposes/applications:
- Radio and television broadcasting
- Live audio engineering
- Two-way radios
- Recorded audio engineering
- Computer usages, such as VoIP, speech recognition and voice recording.
Now, the various types of microphone PCBs are powered by distinct technologies, namely:
- Electret Condenser and;
- Micro Electromechanical Systems (MEMs)
With that being said, let us go into the details of the different kinds of modern PCBs that are powered by Printed Circuit Boards (PCBs).
1. Condenser Microphones
These are one of the oldest microphones, with the first version invented by E. C. Wente in 1916. Today, the condenser microphones have been optimized for modern usage, with many of them using PCBs to hold all the components together.
Here is how the condenser microphone typically works:
- The diaphragm acts as one plate of a capacitor. This is because the condenser microphone may act as a capacitor, hence the reason why it is also called a capacitor microphone.
- The audio vibrations produce changes in the distance between the plates.
- The vibrations can also produce changes in the capacitance, and this is due to the inverse proportion of the plates’ capacitance to the distance between them.
The categories of Condenser Microphones include:
a. DC-biased Condensers
These microphones have the voltage maintained across the capacitor plates, and makes changes with the vibrations in the air.
The DC-biased condenser microphones also have the plates biased with the fixed charge (Q).
b. RF Condensers
These are condenser microphones that have a comparatively-low Radio Frequency (RF) voltage – and this voltage is generated by a low-noise oscillator.
c. Electret Condenser
This is both a technology powering the construction of modern microphones, as well as a type of condenser microphone.
The functions of the electret condenser microphone include:
- Using a permanent charge in an electret material, in place of the externally-applied charge used in traditional condenser microphones.
- Facilitating the embedding of static charge in an electret, via the alignment of the static charges in the material.
Due to the excellent optimizations done here, most of the microphones produced today leverage the architecture and design model of the electret condenser.
The benefits of this choice include:
- Ease-of-manufacturing/production
- Electret (condenser) microphones are high-performance mics.
- These microphones are optimized for a variety of uses, such as built-in microphones used in telephones and sound recording devices, as well as lavalier microphones.
- Electret condensers don’t use polarizing voltage, but instead uses an integrated preamplifier that requires power.
2. Microelectromechanical Systems (MEMs)
This is another technology used in the production of modern microphones, especially with the integration of Printed Circuit Boards (PCBs).
Also called the silicone microphones or microphone chips, the MEMs serve as a “tiny building block or foundation for modern microphones.”
Here are how the Microelectromechanical Systems (MEMs) microphones stack-up:
- The first process is the direct etching of a pressure-sensitive diaphragm into a silicon wafer. The Microelectromechanical Systems (MEMs) processing techniques are utilized for this purpose.
- An integrated preamplifier is added thereafter.
From the architecture and optimization, it is obvious why the MEMs microphone is becoming popular these days.
The following are some of the working principles:
- As a second or secondary semiconductor die, the MEMs have a similar performance as the audio amplifier. In this essence, it aids the conversion of the switch capacitance to an electric signal.
- The sound pressure waves are formed by the Microelectromechanical (MEM) partition.
How Does the MEMs Mic Work?
To have a perfect understanding of how the Microelectromechanical (MEM) microphone works, we will start with the basics.
First, the MEMs-related component(s) is placed atop the Printed Circuit Board (PCB), after which a mechanical cover will be used to protect the component(s).
The second step is the creation or fabrication of a hole in the case. This is done to allow for sound penetration into the microphone. The ideal locations for the fabricated hole are:
- Bottom-ported hole design. This location is used if the microphone is positioned inside the Printed Circuit Board (PCB).
- The top-ported hole design is used if the microphone is located at the top of the case.
The MEMs Construction
The ideal way to construct a Microelectromechanical (MEM) type of microphone is designing a mechanical diaphragm and a mounting structure, which is created on a semiconductor die.
The Structuring of the Semiconductor Die
The first semiconductor die is used as a foundation for hosting or holding the mounting structure and the mechanical diaphragm. There is a secondary or second die, which is required when there is a need for an audio preamplifier. In this case, the secondary die is used as a mean of converting the MEMs’ capacitance to a corresponding electric signal.
Other Types of Microphone PCBs
Besides the condenser and MEMs, several other microphones are in existence. Some of these are recalled from the way back, such as the vintage microphones. Others are:
- Plasma
- Piezoelectric
- Carbon
- Dynamic
- Ribbon and;
- Wireless microphones
Vintage Microphone PCB
As the name implies, this is a “vintage type of microphone PCB” – meaning that it has been in use for many years.
This type of microphone is generally classified under the broader ribbon microphones – which use a thin and corrugated metal ribbon that is suspended in a magnetic field.
Ribbon microphones operate or function by enforcing an electrical connection of the ribbon to the output section of the microphone. This is followed by the generation of electrical signals via the vibrations within the magnetic field.
These are some of the reasons why the vintage mic PCBs are relevant:
- The sound-production capability of the vintage mic PCBs is almost at par with what the modern microphones produce.
- Vintage microphones often use a bidirectional method of sound detection, whereby, sound is detected from both (open) sides of the ribbon.
- The vintage mic circuit boards are ideal for a plethora of people, ranging from recording artists, circuit board engineers, and audiophiles.
How to Choose a Microphone PCB
The selection of microphone PCBs is not limited to the microphone body parts. The choice is always between the two common technologies – Electret Microphone (ECM) and Microelectromechanical Microphone (MEM).
With that being said, we will make a comparison of the ECM and MEM microphones, based on their unique features and differences.
a. Consider the Applications/Use Cases
The first difference between the ECM and MEM modern PCB microphone technologies is based on the use cases or the applications.
Although the MEM is gaining considerable traction, in terms of the microphone uses, there are some cases it wouldn’t be required. An example is the prioritization of the ECM over the MEM when the application has to do with making an upgrade to an existing microphone PCB design.
The Electret Microphone (ECM) PCB is also commonly used for many legacy microphone designs.
b. Does it have Compact Microphone PCB Designs
The Microelectromechanical Microphone (MEM) PCB design is often used to make mics required for space-constrained applications. The condensed or compact design is attributed to the following optimizations:
- A reduction in the circuit board area.
- Including the analog and digital circuits microphone’s construction.
c. What is the Design’s Flexibility?
If you are looking to use PCBs in making mics that would be adaptable to different applications; it is best to use the ECM technology.
The technology supports the use of several connecting options for the microphone to the applications. Examples are:
- Spring contacts
- Wires
- Solder pads
- Pins
Final Words
PCBs can now be used to make different kinds of microphones, such as condenser and lavalier mics. The key to getting it right is comparing the options presented by the Microelectromechanical Microphone (MEM) and Electret Microphone (ECM) technologies.
Overall, make sure the chosen technology adapts to the target applications, offers cost reductions, makes the design flexible and supports an upgrade.
