Teensy MicroMod PCB thickness increased


Well-known member
I'm posting this here as well as the Sparkfun forum, because I feel I'll get more response here. Has anyone who regularly uses Teensy MicroMods noticed that some are difficult to push into the M.2 connector? I received one and measured its thickness. It is 1mm. Others are 0.8mm - this conforms to the M.2 spec - 0.8mm +/-10%. I'm guessing this is to add rigidity because of the failures we widely discussed and complained about. It's difficult to insert into the connector and more prone to bending when screwed down. Oh well... This post is just a complaint really.


Again, a Teensy 4 on a small, one-sided castellated PCB with all the support components would be great. Lots of us use them in finished products and this would be easy and convenient. You could send 1000 to good ol' JLCPCB and I could get them to solder it on my PCBs for me ;)
Hmm. thanks for the heads up. 0.15mm thicker is only like 0.005" which is maybe the thickness of a sheet of paper but still that would certainly create a bigger problem with inserting them. I wonder if it provides a tighter, long lasting fit or if this could damage the M.2 slot?
Again, a Teensy 4 on a small, one-sided castellated PCB with all the support components would be great. Lots of us use them in finished products and this would be easy and convenient. You could send 1000 to good ol' JLCPCB and I could get them to solder it on my PCBs for me ;)

One sided and castellated would be nice ... but Paul has noted some of the following ...

There are about 22 components on the bottom of a T_4.0 - more on the T_4.1 bottom plus QSPI pads and other through holes.

Many of those are there for needed proximity to the MCU core for function - also seems it minimizes wire runs to those needed parts to allow it to fit on the given PCB and pull the signals out from the tight BGA pads.

To make the T_4.1 with other needed BGA signals it had to use the plus sized MCU package.

Also 1.0mm is 25% bigger than 0.8mm ... more bend from prying across the connector sounds perhaps counter productive.
One thing to note is that 1.0mm is very nearly _twice_ as stiff as 0.8mm, so its a massive difference in robustness.
Screwing the thicker MicroMod down requires more force and it's this that worries me.

A T4 with no USB connector and button, would be smaller. Milling a hole to allow for components on the bottom side is a possibility? 1.27mm pitch allows for plenty of pins.
Applying greater force when tightening the thicker MicroMod concerns me. A USB-less T4, smaller in size, could work. Creating a hole for bottom-side components is feasible with the 1.27mm pitch, offering ample pin options.
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I welcome the stiffer MicroMod. The one I have bends alarmingly when in use; MLCCs and BGA pads really do require a stiff board or problems ensue (as we've already discovered with the MicroMod pad issues).

I've looked at making my own board based on Teensy 4 and the PJRC-programmed bootloader ICs, with a square footprint and 1.27mm = 0.050" pitch single in line pins, say 20 pins centered on each edge, with corners free, size about 50mm×50mm to 2"×2". I do want more GPIO (or rather, easier selection of GPIO, me doing parallel buses and such shenanigans), and this would let me either use a board with a routed hole (for castellated style), or SIL SMT headers like Harwin M50-3142045R (which have every second pad in the other direction, making soldering the 1.27mm pitch easier for hobbyists like me). Power and ground pins would have an unconnected pin next to them, for simplicity and safety for us uncle bumbleforks. Both sides of the board would be populated. External reset button, no LED, no pin order compatibility with existing Arduinos, but compatible with Teensyduino.

Now that JLCPCB offers even 6-layer boards in that size for very cheap, and even has some MIMXRT1062CVL5B (extended temperature range version that member ted reported works) available for SMT assembly, this is more interesting than ever before! It is a pity I'm an utter hobbyist with electronics, and although I have successfully designed various boards with SMD components, BGA scares me; moreso trying to route a BGA on a 6-layer board. ("Flux, IPA, acetone, and an old soft toothbrush makes me the solderer I ain't", to mangle a saying old welders have.)
It'd be a lovely derivative I'd be happy to share/develop with others to manufacture on their own (assuming PJRC doesn't mind), for building their own gadgetry on top of Teensy 4, the PJRC bootloader ICs, and Teensyduino.

If the power sequencing allows, it'd be really nice to be able to power it from external 3.0V - 3.3V, at least for I/O; so that depending on the need, one can pick what kind of DC-DC switcher is most useful, from LDOs and RT1062 internal, to high-current, high-efficiency switchers like TI TPS53915. For example, for USB powering, TI Webench says TPS6209733 would only need 1µH inductor, input and output capacitors, and a 10nF cap, to convert 5V to 3.3V at 500mA at better than 95% efficiency, up to 2A at 93% efficiency. (High efficiency makes thermal management so much easier; it's the waste heat that I often have to fight.)
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Sparkfun's answer is to send it back to Digikey. They're not going to address how or why it's happened (an obvious increase in board thickness done by their manufacturer). This underlines why I would trust a similar product from PJRC.