PCB Mounted Vibrator Motors : Best Practice Design

Overview

Assuming there is enough board space, utilising PCB vibrating motors in an application such as haptic feeback is easy. But, there are just a few things to be consider when using them.

RoHS Compliance and Lead Free Soldering

All our motors are RoHS compliant. That means that the parts themselves comply with RoHS standards. 

Furthermore all our PCB motors are compatible with the higher melting / reflow temperatures required as part of lead-free soldering processes. This is mainly of concern with the SMD vibration motors, there is a recommended temperature reflow cart on that page.

If you have any further questions about this, please contact our engineering support team.

Through-hole Pad Sizes

You are securing a through-hole PCB vibration motor with solder to thin copper pads, which are attached to a glass fibre board with glue, so bear in mind that there is some mechanical strain on the system.

Generally there should be no problems, so long as the pad sizes are appropriate for the job. We offer recommended pad geometry on the drawings and datasheets of our vibration motors. If you stick to these guides you should have no problems.

As a general guide we recommend that the holes for mounting pins are drilled 0.3mm wider than the pin size, and holes for electrical contacts are drilled 0.2mm wider than the pin size. As for pad size, we recommend the electrical contact pads be done at your designer's discretion, but that mounting pin pads are at least 2.5x the mounting hole diameter.

For the same reason we recommend against using single-sided PCB's for through-hole vibration motors and in any case this would only be technically possible if one were using a 0.8mm thick board (a very unlikely combination). The thru-hole plating will greatly improve the anchoring of the vibration motor to the PCB.

PCB motors for better EMI supression and filtering

Generally it's best practice in any design to put a small EMC filter across the vibration motor's terminals. This ensures that any minimal electro-magnetic interference (EMI) radiation that is generated by the inductance and commutation mechanism of the motor is prevented. 

This generally isn't a problem with small motors (especially those PCB motors without flying leads) because they all have such a low inductance. By the same token, 0402 Y5V capacitors are cheap and take minimal board space. If EMC is of further concern consider an X2Y filter across the motor terminals or a choke in series. 

Also, grounding the securing pads and pins of the PCB mounted motors can help make a small improvement in EMC output of the vibration motor.

PCB vibration motors affecting component performance

We get asked a lot about whether PCB mounted vibrating motors can affect the performance of other components on the board. The level of acceleration produced by vibration motors (1~2 G’s) is trivial compared to the acceleration experienced when a product is dropped onto the floor (which can be 100’s and even 1000’s of G’s depending on height and and drop surface).

Vibration motors won’t affect the reliability of solder joints, and the PCB will be typically exposed to the same vibration whether the motor is PCB mounted or not (unless some special designs are used).

However we did recently come across a really interesting scenario when designing our latest generation of vibration testing machines. These use small ceramic capacitors to add noise filtering to the analogue outputs of the measuring accelerometers. Some ceramic capacitors can produce electrical noise from vibration, a bit like a piezo electric transducer. You can read more about this here. It is negligible compared to other sources of noise, and some proper component selection can easily solve it.

Securing Flying Leads Against Vibration Metal Fatigue

Most metals when subjected to repeated stress will fatigue. In the case of flying leads, the metal (copper) is both soft and thin. Unsecured flying leads will vibrated, and if they are not crimped and clamped / secured, the point where the inner wire core emerges from the protective insulating cover, will often suffer from fatigue, and the wire will break.

Note also that inside the motor case, the leads are crimped to the motor brushes. It is possible therefore that the wires can also fatigue and break at the point where they enter the motor end-cap. Securing the leads will solve this problem.

There are four solutions to this problem:

• Secure the wires to the board so that they don't vibrate around the solder point. This can be done with hot-melt, epoxy, or cyano acrylate (as shown on the photo right).

• Additionally, one can secure the leads as they enter the end-cap with epoxy or hot-melt if they are likely to be subject to vibration because they are not secured on the PCB.

• Crimp the wires with terminals that can be then soldered to pads or through holes. The crimps shown right are Molex 50061-8000 male crimps which are suitable for the AWG 32 wires found on vibration motors in the Pico Haptic™ range. Although they are intended to be used for wire-wire connectors, they will usefully fit within a 0.8mm plated-through hole, and then be soldered and trimmed. Now the crimp part is spreading the strain over much more wire area eliminating the fatigue.

• Attach suitable crimps and connectors to the wires. These work in just the same way as the Molex crimps discussed above. We offer a range of connectors. Read our vibration motor customisation guide for some suggestions.

In fact this is such a common problem, we've written an application bulletin specifically about securing vibration motor wires!

If you need clarification with, or get stuck with any of the above, get in touch. You can work with our engineers direct and there'll be no pushy after-support.

Now check out some PCB Vibration Motors : The PCB Motor Main Page....