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I use clock oscillators like ACHL-10.000MHZ in pretty much any board that contains a micro-controller. Recently, I've started using MEMS clock oscillators like AMPMAFB-33.0000T for their claimed better ruggedness and reliability.

I was surprised to read in multiple places that both types of oscillators are very fragile against mechanical shock, and especially vulnerable to ultrasonic cleaning.

However, many manufacturers do not mention anything regarding cleaning and they have not responded to my inquiries. For example : microchip microchip dsc1001

My questions are:

  1. Is this true and common to all manufacturers? If yes how are boards cleaned in a fab house ?

  2. Is this only related to low frequency clocks (32 kHz) and 10 MHz+ clock are safe ?

  3. Is there an alternative to these types of oscillators (better ruggedness with good enough accuracy for USART , CAN etc .., communication )? Maybe something mil & aerospace use?

Chris Knudsen
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Eng Sam
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    Generally I trust the manufacturers advice over internet posts. If this were a real issue, you can be sure the datasheet would say so. A failed component can waste millions of dollars in a full production run. And it always gets found out. So it does not benefit manufacturers to hide this kind of stuff. One big failure and they dont get a second chance. Also surprised you havent received any replies. Try getting a field appIication engineer instead of the normal 'contact us' form on a webpage – Kyle B Jun 04 '21 at 14:28
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    I've found abracon to be extremely responsive; my guess is: embargoed country, but it might be any of a number of reasons. Anyway, yeah, it's MEMS, and you don't want to excite the mechanical structures inside with vibrations of a power meant to actively break off things. So, it doesn't sound *that* absurd that you should ultrasonically clean them – it's also not a thing you'd usually have to do with properly manufactured boards, especially with these components. (If cleaning is necessary at all, solvent methods usually suffice.) I think NASA even advises against it due to it being agressive. – Marcus Müller Jun 04 '21 at 14:40
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    It's often helpful to work through your manufacturer's rep or the distributor you purchase from. They have direct contacts with tech and field engineering folks at these companies and can often get you a quick answer. – jwh20 Jun 04 '21 at 14:51
  • @MarcusMüller I thought ultrasonic cleaning is the standard cleaning method after a professional pcb assembler finish the boards to remove flux residues. if not , how are they cleaned ? most boards i have seen look very clean with no flux what so ever – Eng Sam Jun 04 '21 at 15:16
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    well, I never clean my own boards after reflowing – and I can barely see any flux. A machine-pasted fully automated assembly of SMD components can probably do completely without. As said, if you still need cleaning, you do it with a solvent, like clean water or IPA, depending on your flux and your components. – Marcus Müller Jun 04 '21 at 15:18
  • @KyleB you are right that companies are to be trusted over random people online but "the guy's" argument sounded scientific . i qoute "Ultrasonic cleaners can damage quartz crystal oscillators etc. if they induce a mechanical resonance that overloads the crystal itself, its support structure or contacts. Low frequency tuning fork crystals are particularly vulnerable. Any part with delicate sprung contacts is liable to damage so you also have to be careful with switches and presets." – Eng Sam Jun 04 '21 at 15:21
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    @MarcusMüller thank u for clarifying , i usually send my pcb for assembly to local or abroad (PCBway) and i thought they clean the boards as part of the process , I guess i will have to ask to be sure – Eng Sam Jun 04 '21 at 15:23
  • you definitely have to – usually, cleaning is not something contract assemblers do, as they simply set up their machines and fluxes to not leave too much residue. I do know a few products where cleaning is done by default, but it's usually measurement-grade or RF hardware, and it probably costs extra. – Marcus Müller Jun 04 '21 at 15:25
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    @EngSam Well, there IS some truth certainly to the thought that crystals can be broken. In my company, our products are subjected to 6+ foot drop testing, and we have found in the past that crystal oscillators WILL break in that test. As such, we use ceramic oscillators when needed - Not as precise but good enough for what we do. – Kyle B Jun 04 '21 at 17:42
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    I can say also, every single electronic wristwatch made in the last 40-50 years (except maybe the Bulova Accutron) uses a 32khz crystal such as you describe. (I was a "watchmaker" before I became an EE...) After about 10 billion watches manufactured, if these are hyper-sensitive to shock damage it would be pretty well known. To damage one with a simple ultrasonic cleaning.. eh.. maybe, but like you said you'd have to nail the crystals resonance. You know the resonant frequency and all the nodes, so it shouldn't be hard to pick a frequency that doesn't mechanically excite them. – Kyle B Jun 04 '21 at 17:43

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