EEVblog #1027 -  Implantable NeuroStimulator Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: September 25, 2017, 11:09:15 pm
content: What's inside an implantable Medtronics Itrel 3 Neurostimulator designed for Neuropathic pain reduction.Dave tears into the ultrasonically welded titanium case.

author: Brumby
author_rank: Unknown
timestamp: September 26, 2017, 01:42:56 am
content: Interesting.Not that we would have been able to learn much more - but I was wondering if applying some heat from a hot air station to the underside of the case, might have softened the adhesive and allowed the board to be lifted so we could get a better look at the ASIC.

author: EEVblog
author_rank: Unknown
timestamp: September 26, 2017, 04:48:36 am
content: Quote from: Brumby on September 26, 2017, 01:42:56 amIt left like hard epoxy

author: Brumby
author_rank: Unknown
timestamp: September 26, 2017, 04:59:54 am
content: Hmmmm...Fair enough. It's not as if these were built with maintenance in mind!

author: crisr
author_rank: Contributor
timestamp: September 26, 2017, 05:00:56 am
content: That thing @ 13' is probably silica gel or some other kind of desiccant to absorb any moisture left after the case is sealed.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: September 26, 2017, 07:10:19 am
content: Quote from: EEVblog on September 25, 2017, 11:09:15 pmDave, nice tear down. Back in the '90s I worked for a pacemaker company and for pacemakers, the 2 clam shells are welded together in a helium environment with a laser welder, therefore the interior is sealed after welding with high helium content that also keeps things dry inside. The helium allowed the welding to occur without nitrogen yellowing of the titanium case, which, we ran tests in a highly nitrogen environment and discovered the yellowing effect after welding.An interesting fact about titanium welding is that the "dust" that accumulates from the welding is very volatile when exposed to atmosphere (21% oxygen, 78% nitrogen, 1% other). The filters used in the welding cabinet would have to be pulled and immediately placed into a zip lock bag that had a shot of helium injected into it. The technician performing this maintenance would have to quickly carry the filters outside to the parking lot and pierce the bag in an open area and allow it to start fizzling and burning and would beat on it until satisfied that all of the dust had been exposed and the reaction was complete (had stopped burning) before tossing the filters into the dumpster.We always watched this spectacle every month on the scheduled day to insure that the pyrogenic reaction was done before the filters were thrown in the dumpster.Also, you are correct about the differences between this device and the pacemaker. The pacemaker hybrid is much more complex. In our hybrid assembly facility, which was a class 10,000 clean room, we manufactured everything onsite except for the ASICS. We received the wafers, however and sawed the chips off of the wafers and placed them into special containers that we developed. This was done outside of the assembly area in a special room. The saw had air bearings and turned at very high RPMs. This machine was very specialized and very precise.The substrates were made onsite from green tape. These substrate boards had 9 layers and once the shape was cut from a "cookie cutter" from the pliable green tape form, then had all of the vias punched from a special machine that was developed specifically for this process. The vias were filled with a gold paste under very high pressures and the traces were done in a similar manner. Once all operations were done, the substrates would get baked in a very long oven which had a conveyor made from a chain like construction made from stainless steel.I could go on and on about the different processes. My job was to study new machines that was purchased for specific operations/processes and to custom modify them to do specifically what we needed it to do. We also created and designed some of our machines, such as the laser welder mentioned above, when we could not find what we wanted on the market. As our processes matured, to revisit the machine and either modify to hone in on the design or make recommendations about future machine purchases. I had a blast with that dream job.It all ended when the parent company decided to sell the pacemaker division to a rival company who only wanted our pacemaker leads, which were at the time, the best in the world. After the new company plundered that technology, all 1500 employees were laid off. This was in 1999, I started with the company in 1989, and was laid off on my 10th anniversary with the company.

author: EEVblog
author_rank: Unknown
timestamp: September 26, 2017, 07:36:01 am
content: Quote from: tpowell1830 on September 26, 2017, 07:10:19 amOuch

author: tpowell1830
author_rank: Frequent Contributor
timestamp: September 26, 2017, 05:42:52 pm
content: Quote from: EEVblog on September 26, 2017, 07:36:01 amOuch, indeed.

author: Teuobk
author_rank: Contributor
timestamp: September 27, 2017, 05:41:38 pm
content: Wow, I haven't seen one of those in a while!Here are some answers/tidbits:- Back in the 1990s and into the early 2000s, Medtronic maintained its own fab down near Phoenix- The "clinician programmer" you want for the Prime Advanced device is the N'Vision (model 8840), a blue-cased touch-screen job that occasionally comes up on eBay- The reed switch was used by the patient to disable/enable the neurostimulation as required. Certain activities were incompatible with active neurostimulation, so there needed to be a way for the patient to temporarily turn it on or off.

author: orion242
author_rank: Unknown
timestamp: September 28, 2017, 01:12:46 am
content: So how were these triggered?Did the patient trigger them with a magnet, was it just a time release, or did it monitor something and fire based on some logic/condition?

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 28, 2017, 03:31:22 pm
content: I remember looking for the promised teardown after that mailbox. It has turned out not to be a disappointment.

author: Teuobk
author_rank: Contributor
timestamp: September 29, 2017, 09:36:04 pm
content: Quote from: orion242 on September 28, 2017, 01:12:46 amThe clinician would set up a stimulation program, which consisted of an endless train of pulses. The polarity, pulse width, amplitude, and frequency could be configured. The device would also automatically emit a smaller but longer pulse of the opposite polarity to keep the overall DC value zero, which would prevent galvanic corrosion of the stimulation leads. Each electrode could be assigned a positive or negative polarity or be switched off. On the Itrel 3 (but not all neurostimulators), you could also use the neurostimulator case as an electrode, though usually only for the "return" electrode.There were various other options, too, such as cycling (e.g., running for 10 minutes, then off for 10 minutes, then repeating) and soft-start (gradually ramping up the amplitude of the pulses over time).It was all open loop back in those days. More recent neurostimulators have added sensors to detect certain types of movement, for example, and then adjust the stimulation in a configurable way.

author: orion242
author_rank: Unknown
timestamp: October 09, 2017, 03:07:31 am
content: Thanks.Makes total sense after diving into these on the internets. Incredible they can figure out where to place them, how to set the "dose", etc.