Rules of a Medical Device Tear-down
When it comes to a medical device tear-down, you must protect yourself, protect the device, and protect your liability. Here are seven tips to help you safely take apart medical devices. While the tips focus on medical equipment, these tips can apply to general tear-downs of electronic devices.
1. Remove Sources of Power
Often, portable medical devices ship with “plug packs” or external power supplies. External power supplies are relatively safe when high to low voltage conversion is done outside of the device. However, many devices have a built-in power supply, which means high voltage can be present inside the device.
When possible, disconnect the power supply to remove possible accidental short-circuits. For example, screws or parts removed on a device might fall onto a circuit board and short out a connection. This may cause the device to malfunction or even break.
Look Out for Large Capacitors
99 percent of the time, when you’re taking apart a medical device, the capacitors inside of the device are low voltage – usually 25 volts or less. The capacity of these capacitors can be very high, sometimes on the order of one or two farads (actual farads, not microfarads). This can be an issue if you accidentally short the capacitor out with a screwdriver, but not harmful to touch. Some devices though, like defibrillators and x-ray machines, can hold several high voltage capacitors. These usually look like small soda cans with two (sometimes more) contacts. Capacitors can hold hundreds or thousands of volts and can cause serious harm or even death if mishandled.
Capacitors can sometimes spontaneously develop charge, even when not in use, so they usually have built-in discharge resistors to keep them discharged all the time. But, it’s never a good idea to assume the safety devices are working without checking them. High voltage capacitors can be extremely dangerous to work with. If you are uncomfortable with knowing how to check or discharge them safely, it’s best to leave them alone. For more information on capacitor safety
Check for Batteries
Backup batteries are common in medical devices. Batteries utilize a variety of different chemistries. More common with modern equipment are lithium-ion polymer batteries (LiPo), but you may still run into nickel-cadmium/metal or sealed lead acid (SLA) batteries. There are pros and cons to each battery technology, but all of them need to be handled with care.
LiPo batteries, which are common in most medical devices, laptops, smartphones, etc., are very energy efficient for their size and weight. However, these batteries can also be hazardous. LiPo batteries, if shorted out or punctured, can react violently as gas builds up in the cells. As gas builds up, pressure inside the battery increases, and usually causes the battery to swell or rupture and may release smoke. More seriously, the battery can explode into flames. When this happens, the battery, depending on its size and structure, can go into thermal runaway and release around 300+ kilojoules of combustion energy within a few seconds with the internal temperature reaching up to 900C. Thermal runaway means that the neighboring cells of the battery can also rupture or explode, causing a chain reaction of explosions. (Note, for the off chance it does happen to you, DO NOT attempt to put out a lithium ion fire. Leave the building immediately and call the fire department).
You can avoid this by making sure that the battery contacts are not shorted out when removing or storing the battery. Often there will be guards to help protect against this. Make sure to examine the battery for signs of failure, such as bulging or swelling. If you notice a battery with these signs, do not continue using it. Order a replacement battery and dispose of the old battery at a proper recycling center. Alternatively, if you have an agreement with a battery provider, make note of the the issue and return the battery to your provider. For more information on batteries see the following video:
2. Disinfect Inside and Out
Opening up a medical device can be …interesting. In the words of Forest Gump, “you never know what your gonna get”. For used medical devices, especially devices like infusion pumps which handle liquids, the inside of the device can get dirty with unknown materials. These materials may be hazardous.
When you clean the device, make sure to use your provider’s guidelines for infection control. In general, wearing gloves and disinfecting the device are a minimum. For most plastics, rubbing alcohol or Lysol wipes are safe to use. Diluted bleach can also be used. CaviCide is often a preferred disinfectant of many infection control programs, but it is known to harm many plastics.
A best practice would be to contact your equipment manufacturer for a safe recommendation that complies with your infection control department . If needed, you can clean circuit boards with high value alcohol, i.e. 99 percent isopropyl alcohol. Contact cleaner can also be used for board interconnects that have developed grime or corrosion. Using the wrong cleaner can cause damage to equipment both functionally and aesthetically.
3. Wear an anti-static wrist strap
Static electricity can be incredibly destructive to many different types of electronics. The classic example of this effect is shuffling your socks across a carpet. This effect is called triboelectric charging, and it allows your body to build up a substantial static charge. During this process, your body can develop a charge as high as 25,000 volts or more! Fortunately for you, your body can’t hold much of a charge and will dissipate this built up voltage in a sometimes painful, but ultimately harmless spark.
But, while you can withstand a several kilovolt shock from static electricity, electronic components can not. What feels like an annoying shock to you is like a bolt of lightning to a transistor. The gates within microchips can be very sensitive to high voltage, leaving permanent damage. Electronics can be permanently damaged from just a few hundred volts. So, if you were working on an electronic device, you could damage a device without even feeling it!
Fixing damaged caused by static discharge can also be extremely difficult. Static discharge may completely break the device. Or static discharge may cause the device to malfunction or become unstable under certain conditions, such as when the damaged circuit is only accessed occasionally. Often, static discharge damage can require replacing the entire circuit board.
This is why anti-static wrist bands are important. The wrist straps are simple devices: they have a strap that goes around your wrist with a metal conductor on the inside. The metal conductor of the wrist strap is connected to a large value resistor (usually about 1 MOhm). The last part of the wrist strap is an alligator clip. To use the straps properly, the alligator clip must be attached to the metal of the electronic device you are working on, and the conductor in the strap must be in contact with your skin.
The wrist strap, with help from the resistor, will gradually remove the static charge in your body and bring you to the same voltage potential as the device you’re working on. This effectively eliminates the chance of you developing a potential difference than the board/part you are working on. An example of a teardown using an antistatic strap is shown below
4. Remove Dust
The consensus for removing dust and critters vary for electronic equipment. Vacuums can work if special precautions are taken. The nozzle for a standard vacuum cleaner can generate a large amount of static electricity and could discharge back onto the circuit. Generally, to use a vacuum safely with electronics you need to use a conductive metal nozzle which is referenced back to the device you are working on (like the wrist strap example above). Specialized vacuums exist for this, but it is possible to convert or make your own nozzle to get around this problem.
Compressed air canisters can also help dislodge dust, if used properly. The single most important fact when dealing with canned compressed air is that air is not the only thing in the can. Cans of compressed air have a refrigerant compound mixed in them, which can leak out. When using compressed air, make sure you are always holding the can straight up when spraying. Turning the can sideways or upside-down can cause the refrigerant to spray out, covering the electronics. Before using the can on electronics, it’s a good idea to spray it into open air, away from other people, to clear any buildup of liquid in the nozzle. Never spray compressed air at yourself, others, or anything you do not want refrigerant possibly sprayed on.
Compressed air can also be hazardous to breathe in directly. High concentrations of refrigerant from the compressed air in your lungs can cause suffocation, so make sure to use it in a well-ventilated area. You should also wear safety goggles and a mask to protect against dust blowback and possible refrigerant spraying back at you.
You can also check with your organization or the manufacturer of the equipment to see if there are recommended methods or tools for cleaning.
5. Be Gentle
Brute force and technology rarely go together. While some devices may require some force to open, such as when the manufacturer secures bolts or screws with Loctite to prevent tampering. But often, the use of force means you’re probably doing something wrong or there is an obstruction. For example, a circuit card slot may develop oxidation or corrosion, which can make inserting or removing expansion cards difficult. Forcing the card in or out of a slot may bend the pins in the slot.
Older electronics are especially subject to this. Many times, an EEPROM chip (the chip which holds system memory) may be held in with a socket. If the socket becomes corroded, the chip may become very difficult to remove. Forcing the chip out may break pins off the chip or, even worse, pull the socket completely off the circuit board!
Think twice before changing screens
The design and construction of medical devices can vary wildly. But, one aspect of modern medical devices are built-in LCD displays. As a consequence of companies reducing cost and size of their products, screens are often very tricky to reattach. The major difficulty has to do with the method of connecting the screen to the mainboard. Sometimes, with older or larger devices, there will be a signal cable connection with a proper molex (usually a plastic socket and plug), which is easy to remove and reattach. However, many medical devices use a Flexable Flat Cable (also known as a FFC or “flat flex” cable). These cables look like ribbons and are both fragile and difficult to work with.
These cables may connect to the board with a plastic socket, which can make disassembly easier. Flex cables usually run directly behind the screen. Often, screens are held in place with tape. Removing the cable is easy enough but reattaching the flex cable onto the board can be very difficult and time consuming.
So, unless it is necessary or you are specifically looking to replace the screen or logic board, leave the screen alone. Generally, the fewer things you need to take apart, the less likely complication are. Below is an example of a tear-down with FFC cables
6. Document your Work
Take lots of pictures or videos while taking apart the device. You will eventually run into a device that has dozens of screws and odd construction techniques. The device you are working on may also have several wires running between boards interlinking them. The tear-down is the easy part, and it can be tempting to start removing parts quickly, while thinking “this will probably be straight forward to re-assemble,” only to end up with several leftover screws and a non-functioning unit. One technician I knew jokingly called these “bush” screws. He said these were extra screws that when you were finished you just threw them in the bush and pretended like they did not exist instead of taking a part the device and searching for where the parts should go.
Taking a lot of pictures and even videos of the teardown will help you reassemble the device. For example, if you have something half apart, and realize you need to purchase a special part or tool, you may forget what you have taken apart previously. Your records can help jog your memory. Taking pictures can also provide supporting evidence of the work you have done. Documentation is your friend, if and when you need to prove your work was done correctly.
7. Understand the Terms and Conditions of the Device Warranties
Be aware of the consequences your work will have on the warranty of the device. If you are re-manufacturing the device this is not necessarily an issue, since you would not have a warranty. And if you have a warranty, you probably will not be trying to repair the device yourself. That being said, you may be attempting to clean the device internally, due to a known spill or dust buildup. There are also instances when modifications need to be made to equipment, either for improvement of the device that is not clinical in nature, or a required modification due to a recall.
So just remember, if you are trying to repair a device for your healthcare organization, make sure you understand the liability impacts of your work. Many original equipment manufacturers (OEM’s) have reasonable right-to-repair mentalities, but there are some who do not! There are legitimate reasons for OEM’s wanting to discourage non-trained individuals from working on their devices. When a company is providing a warranty to their product, they do not want someone “untrained” taking the device apart. Many OEM’s may require you to take training with them in order to consider you competent and trustworthy to work on the equipment.
A best practice is to check with your OEM or third party device supplier to clarify what the terms of the warranty are and, when possible, get a clear picture of what kind of service is allowed prior to purchasing a device. If your department’s responsibilities conflict with the medical device supplier, you can work with your purchasing department towards a solution.
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Let us know in the comments if you have any other tips when you take a part medical devices!
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Authors: Kevin Williams and Brian Bell
This material is based upon work supported by the National Science Foundation under grant number 1700649. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the National Science Foundation.