SMD Buzzer Selection Guide: Key Factors, Reflow Soldering and Application

1.Introduction
2.Two types of Core Technologies
3.Balance Package and Size with Acoustic Output Miniaturization
4.SMT Assembly and Reflow Soldering
5.Application-Based Selection Matrix
6.Pre BOM Checklist and Next Steps

Introduction
Things are becoming smaller. But that's not the case today, it's the reality of electronic engineering. From creating a fitness tracker to a smart home sensor, or an in-vehicle warning system, this downward trend of achieving maximum functionality in the smallest possible PCB size can never be ignored.
The Buzzer is definitely the final piece of hardware that one would be think about while designing the layout and that's not a smart idea. Get the wrong part and it will not survive reflow, will require more power than your battery requirements or will not fit the enclosure that team agreed upon.
This blog consolidates useful, hands on information that saves-time at the design level including types of technologies available, trade-offs of packages, reflow considerations and a quick application matrix to help you select the right SMD buzzer before finalizing your BOM.

Two types of Core Technologies
There are two types of core technologies, magnetic SMD buzzers and piezo SMD buzzers.
The quickest way to determind your options is to know the physics of each type.
Magnetic SMD buzzers are based on electromagnetic principle. A metal diaphragm is vibrated by a coil, creating sound. Usually they have many operating voltages(in the low 1.5V to 5V range), making them easy to incorporate into most projects involving MCUs. The downside is a draw on power: magnetic buzzers consume more power than piezo buzzers, so if you're powering it with a coin cell or a little LiPo, power is an important consideration. The plus side is that their lower resonant frequencies help to create a round and full sound, which can be beneficial for many people, particularly those with hearing difficulties in busy places.
Piezo SMD Buzzers use a piezoelectric ceramic disc element. If a voltage is applied to the disc it will bend, but if a reverse voltage is applied, the disc will bend back the other way. This mechanical flexing helps to create sound with a high efficiency. When designing ultra-thin devices and battery-powered devices, current consumption is typically in the microamp domain, making piezo element the preferred material. Burrier tone is sharper and higher in pitch, which fits for an unambiguous alarm, but may be very piercing in confined areas.
Passive vs Active, which do you need?
If the buzzer is active, its own oscillator circuit is included. If a constant DC voltage is applied, it beeps at a constant frequency. This way has low BOM line count, no firmware complexity and easy to drive.
To make sound, a passive buzzer requires an external PWM. That will help your MCU to perform more tasks, but gives you complete freedom over frequency and tone patterns, which is helpful when your MCU requires unique versions and variations of alerts (warning, confirmation, fault… etc.) or your local regulations have a specification for alarm frequencies.
It depends on the level of ruggedness that is desired versus the minimalization of the firmware and circuit.

Balance Package and Size with Acoustic Output Miniaturization
Small is good, but tiny has consequences. As the package begins to get smaller, here's what happens.
Common SMD Package Sizes
There are only a few footprints in the industry. The 5 x 5 mm, 8.5 x 8.5 mm and 9 x 9 mm packages will be used repeatedly from the catalog lines. 
The Physics You Cannot Ignore
Size of the radiating surface is correlated to Sound pressure level (SPL), the number in dB indicating how loud a buzzer is.  Lower SPLs with smaller diaphragm and less air moved. This is something that can't be avoided. If you used 5x5mm  buzzers instead of 9x9mm, the output will not be the same at the same drive voltage.
Resonant frequency also varies with size. Smaller buzzers vibrate at higher frequencies which can also be a good thing (loud, alert, attention catching sounds) and a bad thing (high, loud noise in hospital/medical setting where quieter warning is desired).
Sound Port Direction: Side-Port vs. Top-Port
This detail has a greater impact than most engineers appreciate in designing an enclosure.
The top port buzzer emits the tone from the top (which is the face of the PCB). It will function if you have a grille or opening over the enclosures' leg directly over the buzzer's mounting point.
The side-port buzzer on the side of the package emits sound. It is well suited for designs that place the PCB flatly in the inside of a closed box with a vent located on the side wall in which the sound must be conducted sideways towards the vent.

SMT Assembly and Reflow Soldering
Buzzers are sensitive elements to sound. All are components that can be adversely affected by heat, moisture, reflow flux residues if reflow is not performed correctly.
Temperature profile during Lead-Free Reflow
In terms of the manufacturing process, lead free solder paste and as a rule peak temperature of 482°F(250°C) to 500°F(260°C) in the range of RoHS compliant manufacturing. Rating for maximum peak temperatures should always be checked in the datasheet before finalizing a specific pick and place program.
One of the problems with running a profile hotter than spec is that you could damage your profile permanently but it may not show up until the board goes into function.
Protecting Against Heat Damage
In the case of magnetic buzzers, too much heat can reduce the ability of the internal magnet. As the SPL decreases, the frequency changes and the part no longer sounds as loud as it is supposed to but is definitely quieter. This type of deterioration is difficult to detect at ICT and can only be revealed by final acoustic control.
In the case of piezo buzzers, too fast or too extreme temperature might lead to cracking of the ceramic disc. When a ceramic cracks, output is lost, it comes on and off or it will fail without warning. These failure modes can be avoided by ensuring a controlled thermal profile and with the right component rating.
Protection of the buzzer when cleaning PCB
Many SMDs do not have a 'sealing' mechanism against liquid ingress. When there are aqueous cleaners following a soldering process, such as automotive or medical programs, the sound port of this buzzer needs to be protected from flux remover, rinse water and flux residue.
However, if your line does not include board cleaning, then this is of no concern. Only wash if the buzzer is labelled, or you plan to label a buzzer because you plan on washing it — do not assume that the buzzer will be washed unless specified in the datasheet.

Application-Based Selection Matrix
Every market is unique about the end-user priorities. Let's take a practical look.
Medical Devices and Smart Wearables
Size and power are the major limitations. Most wearable applications have a footprint of 5x5mm. The current draw must be kept to whatever it is the battery chemistry and capacity can handle.
Alarm frequency is important for the clinic. There are frequency ranges indicated in medical alarm standards like IEC60601 and its associated standards, such as 2 to 4kHz, as the human ear is most sensitive at the frequencies indicated and the background noise in clinical environments are usually lower than 1kHz. Test the SPL level of the buzzer at the required test distance and ensure the resonant frequency is in the required frequency range.
Automotive Electronics (ADAS, Dashcams, Telematics)
The headline spec would be temperature range. Consumer/office grade parts are usually rated at 158°F(70°C) or 185°F(85°C), automotive parts begin at 185°F(85°C) and are often rated at 221°F(105°C) or higher. When mounted close to the engine bay or puts engine exposure on the dashboard, check the maximum temperature rating and then reduce the output.
Smart Home and IoT Sensors
Customers are very cost-sensitive within this segment. The fortunate aspect is the acoustics are typically less demanding; you don't need sufficient sound pressure level (SPL) to be heard throughout a factory, you need it to be heard across a factory room.
A smart home that is not built inside a confined space is more concerned about volume (SPL) at distance rather to go with a wearable application. Most residential situations require a buzzer to provide adequate alerts with a 9x9mm piezo buzzer having a volume between 85 dB and 90dB SPL will suffice.
Tape and reel packaging have become common practice in automatic SMT production lines. Check if the correct buzzers are in the reels as ordered to the length as the feeder of your line. 

Pre BOM Checklist and Next Steps
Check these parameters before you lock the component:
Drive voltage: Make sure that the buzzer's rated operating voltage matches your supply voltage and logic levels. Please make sure to read the minimum and maximum.
Current draw: Check the peak current limit at the rated voltage with the regulator's output capacity and your batteries discharge budget.
Resonant frequency: Match to the requirement of the alert frequency of the usage. Test the frequency at rated voltage to see if it is within your target range, and not just the nominal test voltage.
SPL rating: Just ensure that the SPL measurement distance is compared to your products acoustic test requirement, with any enclosure attenuation taken into account.
Package size and package height: Check with your PCB keep-out areas and package clearance. Be careful of the height spec, buzzers are often one of the highest outlined parts on a board.
Check port direction: Make sure it's top port or side port by testing with your enclosure.
Packaging format: Make sure tape and reel are available for production. Compare numbers of reels played to forecast.
Temperature rating: Ensure that your operating and storage temperature range is within the specified limits.
Wash label: Required if your line uses aqueous cleaning post-reflow.

Bestar's engineering team works directly with design teams from first schematic through mass production. If you are evaluating SMD buzzers for a new program — or troubleshooting an existing design — reach out to request samples or a technical consultation. We can recommend specific part numbers based on your drive circuit, enclosure geometry, and acoustic requirements, and we support custom specifications for programs that fall outside standard catalog options.