From: Dwayne Reid <dwayner@planet.eon.net>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Thu, 2 Jul 2020 13:02:19 -0700
Subject: Re: [EE] Specifying the right electrolytic capacitors for long	(10
 year) operating life?
Thread-Topic: [EE] Specifying the right electrolytic capacitors for long	(10
 year) operating life?
Thread-Index: AdZQrVKMv2qNJS8ITt6Jyyc0nIpmdg==
Message-ID: <3a880f7aeabb3600b2925c7dd3f2e7eb@mtlp000085>
References:
 <CAOFvGD73Kei2Ck0K4D=QVa6+Pvg0=8VjR5y54H9FLHqznYrQmw@mail.gmail.com>
In-Reply-To: <CAOFvGD73Kei2Ck0K4D=QVa6+Pvg0=8VjR5y54H9FLHqznYrQmw@mail.g
	mail.com>
Reply-To: Microcontroller discussion list - Public. <piclist@mit.edu>
Accept-Language: en-US
X-MS-Exchange-Organization-SenderIdResult: Pass
X-MS-Exchange-Organization-PRD: mit.edu
X-MS-TNEF-Correlator:
received-spf: Pass (protection.outlook.com: domain of planet.eon.net
	designates 209.171.16.91 as permitted sender)
	receiver=protection.outlook.com; client-ip=209.171.16.91;
	helo=cmta18.telus.net;
dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
	d=mitprod.onmicrosoft.com; s=selector2-mitprod-onmicrosoft-com;
	h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;
	bh=cVwmfiz6p0H3IbQlIKp35iob2YTqABl96U93ZDg/5FQ=;
	b=RfwNqbpeNjKMV0IvaD6mjM/f+DIb/CgtPJkpGCD2bs1MZjv7e8w4zi1omrw/WHZxdJptLVUPXl6tfVrTsfAMnHk7OxRqqv7La+P8QmDIMZFK0BFC215WMJJQvY/4bA28RiAq784DumTQc2p2U14nQfOBmi5kHVYonAJsAF9MDis=
authentication-results: spf=pass (sender IP is 209.171.16.91)
	smtp.mailfrom=planet.eon.net; mit.edu; dkim=none (message not signed)
	header.d=none;mit.edu; dmarc=bestguesspass action=none
	header.from=planet.eon.net;
errors-to: piclist-bounces@mit.edu
list-id: "Microcontroller discussion list - Public." <piclist.mit.edu>
list-post: <mailto:piclist@mit.edu>
x-beenthere: piclist@mit.edu
x-mailman-version: 2.1.6
x-authority-analysis: v=2.3 cv=A+ASwJeG c=1 sm=1 tr=0
	a=Dd/bvHhForHuZnb7ytaWSQ==:117 a=Dd/bvHhForHuZnb7ytaWSQ==:17
	a=HpEJnUlJZJkA:10 a=kj9zAlcOel0A:10 a=F07sB3KiAAAA:8 a=Gz7s5_CCAAAA:8
	a=D1QUtfyEAAAA:8 a=WVHiL177AAAA:8 a=1alZ_kbrw2wfBMJZTKoA:9	a=CjuIK1q_8ugA:10
	a=iZdX4GlK_F8A:10 a=SxPZiMLqSpAA:10 a=n1uYnq2louoA:10
	a=8rYrM0obaTRgCqsvCuYq:22 a=_yt5nuqSr3Ff_nZNByN4:22	a=zz8lhgAq7brTZQd0Oeqi:22
x-topics: [EE]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0

Hi there, Jason.

I use Tantalum capacitors for RC time delays.  Good quality=20
electrolytic caps might give you good results - or not.

Both bead-type and hermetically-sealed Tantalum caps have been=20
reliable for me for decades.  I do not have reliability data for SMT=20
Tantalum caps - I just haven't been using them long enough.

However, do NOT ever use a Tantalum cap on a high-current power=20
rail.  They fail if exposed to even a momentary over-voltage=20
transient.  The end result is often a hole in the PCB where the=20
capacitor used to be.

dwayne


At 10:38 AM 7/2/2020, Jason White wrote:
>Hi everyone,
>
>I'm looking to learn about the critical parameters in specifying the
>"correct" electrolytic capacitor to last a long time (10 years).
>
>I suspect it comes down to selecting a "long life" series capacitor from a
>reputable brand (perhaps Nichicon or Panasonic?) with a high hour and
>temperature rating, low ESR, and significantly higher than needed voltage
>rating.
>
>I have a safety related circuit where I have no choice but to use two
>"large value" electrolytic capacitors. Wide temperature range, very loose
>tolerance and performance expectations from the capacitors. I'd like the
>two capacitors to "last" 10 years of having power applied.
>
>The first capacitor is being used in a RC timing delay. Consequently, the
>"ripple" current would be in the single digit microamp range. I'm concerne=
d
>about this capacitor's capacitance and leakage staying in spec over
>temperature and time. Low duty cycle.
>
>The second capacitor is being used to provide bulk "high-ish voltage"
>decoupling capacitance to an electric motor. The supply impedance to the
>motor rail is high. I'm concerned about this capacitor's ESR and
>capacitance staying in spec over temperature and time. Ripple current is
>assumed to be similar to motor supply current of ~3 amps. Low duty cycle.
>
>Tambient-max=3D95C
>
>Any advice, anecdotes, or links to relevant literature would be appreciate=
d.
>
>--
>Jason White
>--
>http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>View/change your membership options at
>http://mailman.mit.edu/mailman/listinfo/piclist


--=20
Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
780-489-3199 voice   780-487-6397 fax   888-489-3199 Toll Free
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.