[Amps] Amps Digest, Vol 172, Issue 20

Wed Apr 12 12:21:06 EDT 2017

Maybe the mat was made in China *after* the contract was signed?

Gary...wa6fgi

On 4/11/2017 3:55 PM, amps-request at contesting.com wrote:
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> Today's Topics:
>
>     1. Re: Tubes, transistors, and 'abuse' (Jim Garland)
>     2. blowing up CMOS (Steve Wright)
>     3. Flex Amp Ad (Richard Solomon)
>     4. Re: blowing up CMOS (Bill Turner)
>     5. Re: blowing up CMOS (Bill Turner)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 11 Apr 2017 14:17:04 -0600
> From: Jim Garland <4cx250b at miamioh.edu>
> To: Doug Ronald <doug at dougronald.com>, amps at contesting.com
> Subject: Re: [Amps] Tubes, transistors, and 'abuse'
> Message-ID: <9bdb59e9-8278-7f62-7f13-92f9e1db7989 at miamioh.edu>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> Doug,
>
> I agree that those numbers sound low for an ESD mat, but I'm not
> surprised that the values of the two measurements were about the same.
> The thickness of the mat complicates the results when the probe spacing
> is comparable to the mat thickness. When that happens, the mat is acting
> like a bulk three dimensional object for the close-spaced probes, but a
> two-dimensional object for the widely separated probes. In the
> theoretical limit of an infinitely large but infinitely thin mat, I
> believe the two measurements would agree.
>
> 73, Jim W8ZR
>
>
> On 4/11/2017 2:04 PM, Doug Ronald wrote:
>> I just tested the anti-static mat in front of me with an ohmmeter, and was
>> amazed to see the resistance was not linear with distance. The mat was on an
>> insulating surface, and with the probes as close as possible without
>> touching, I got 42 kilo ohm. At the opposite ends of the mat I got 56 kilo
>> ohm. The mat is about 5 mm thick, and seems to be all the same uniform
>> material. The backside behaved the same way. There may be some inner layer
>> that is of much greater conductance - can't tell...
>>
>> -Doug W6DSR
>>
>> -----Original Message-----
>> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of
>> donroden at hiwaay.net
>> Sent: Tuesday, April 11, 2017 12:49 PM
>> To: amps at contesting.com
>> Subject: Re: [Amps] Tubes, transistors, and 'abuse'
>>
>> Disagree.
>> Don W4DNR
>>
>>
>> Quoting MU 4CX250B <4cx250b at miamioh.edu>:
>>
>>> Speaking of high resistance mats, an interesting property is that the
>>> resistance between any two points on the map is the same, no matter
>>> the distance between the points. In other words, it doesn't matter
>>> whether you put your test probes a cm apart or 10cm apart, the
>>> resistance will be the same. That's why the resistance of a flat mat
>>> is always specified in ohms, unlike three-dimensional materials whose
>>> resistivity is specified in ohm-cm. In two dimensions, resistance and
>>> resistivity are the same thing.
>>> 73,
>>> Jim w8zr
>>>
>>> Sent from my iPhone
>>>
>>>> On Apr 11, 2017, at 12:42 PM, MU 4CX250B <4cx250b at miamioh.edu> wrote:
>>>>
>>>> Ah, Wise move on your part, Manfred. I wouldn't wear it either! Your
>>>> former boss needed higher level Technical Support!
>>>> Jim
>>>>
>>>> Sent from my iPhone
>>>>
>>>>> On Apr 11, 2017, at 12:39 PM, Manfred Mornhinweg <manfred at ludens.cl>
>> wrote:
>>>>> Jim,
>>>>>
>>>>>> Manfred, I think  you are worrying needlessly. A grounding wrist
>>>>>> strap connects to the mat, not to the device under test. ESD mats
>>>>>> typically have a resistance in the 10E7-10E8 ohm range. The mat on
>>>>>> my workbench has a resistance too high to measure with my Fluke
>>>>>> 87-V. The mats discharge static buildup, but neither they nor the
>>>>>> wrist strap pose any safety hazard.
>>>>> Fine then. But the straps that one boss at the job wanted me to wear
>>>>> were all metal. Indeed they connected to the mat - but to a metal
>>>>> frame surrounding the static dissipative (highly resistive)
>>>>> material, and that frame was grounded. In the end, that wrist strap
>>>>> was grounded with a very low resistance, and I refused to wear that,
>>>>> for safety reasons.
>>>>>
>>>>>> I have lost MOSFETS from not taking adequate ESD measures. Some of
>>>>>> the older devices, especially, are very easily burned out.
>>>>> There are some that don't have the built-in zener protection - those
>>>>> are indeed fragile. Laser diodes (or rather their built-in
>>>>> photodiodes, I think) are also said to be very sensitive to static.
>>>>> I have handled such devices with no more precautions than the basic
>>>>> ones, and never lost any.
>>>>>
>>>>>> There's a reason all semiconductor distributers (Mouser, Digikey,
>>>>>> etc.) pack their components in ESD envelopes!
>>>>> Yes, and that's actually a good thing to do, and I do it too, when I
>>>>> ship something sensitive. My fundamental point instead is that
>>>>> thoughtlessly used grounding straps and the like can CAUSE more risk
>>>>> to the parts than they help prevent! I have seen people who put on
>>>>> such a grounding strap, next to their static-safe workbench, and
>>>>> then think that nothing bad can happen. Then they reach over to a
>>>>> drawer and withdraw a MOSFET by the gate terminal, and !ZAP!, they
>>>>> discharge the entire drawer through that MOSFET!
>>>>> My practice instead is to first get hold of the drawer, to put
>>>>> myself at its potential, then pick up the MOSFET by anything but its
>>>>> gate terminal, then walk over to my desk, touch the desk, then place
>>>>> the MOSFET on it. In doing so, I have already double safety in it:
>>>>> By avoiding to touch the gate first, and by equalizing the potential
>>>>> between myself, the desk, the MOSFET, and anything else, in a safe
>>>>> way.
>>>>>
>>>>> Most of this caution exceeds what's needed, but as you say, it's
>>>>> smart to be careful. And I would add that it's good to be smart!
>>>>> In the sense of thinking where static charges will form, what can be
>>>>> charged relative to what, which items could carry significant
>>>>> leakage current, and so on, and then acting accordingly. That's much
>>>>> safer than using a mat, a strap, and stopping to think about the
>>>>> matter, which is what I have witnessed some people doing!
>>>>>
>>>>> Manfred
>>>>>
>>>>> ========================
>>>>> Visit my hobby homepage!
>>>>> http://ludens.cl
>>>>> ========================
>>> _______________________________________________
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>
> ------------------------------
>
> Message: 2
> Date: Wed, 12 Apr 2017 08:38:17 +1200
> From: Steve Wright <stevewrightnz at gmail.com>
> To: amps at contesting.com
> Subject: [Amps] blowing up CMOS
> Message-ID: <ef41118f-eacf-13a6-c239-6c19aca75349 at gmail.com>
> Content-Type: text/plain; charset=windows-1252
>
> On 12/04/17 04:00, Manfred Mornhinweg <manfred at ludens.cl> and one other
> wrote:
>>>> ground wrist strap?
>> And in this regard I must have missed something... Because I don't
>> have an anti-static mat, nor do I have a grounding wrist strap. [....]
>>    I can't remember having lost any of them due to static while
>> handling it. In fact the only case I can remember when I did lose
>> something to static was a case of sheer stupidity (stupid action trimmed)
> Another pearl from Manfred.  Hiya mate, hope you are well!
>
> Many people don't know how to hand-over-hand bond their path in front of
> their movements, or else they don't have the level of forward-planning
> and thinking that is required to automatically do it.  Basically, you
> never move the vulnerable component to a new area unless your spare hand
> has touched it first.  So you would pick up the static-free bag with the
> component already bonded to the bag, and now you have bonded your body
> to the bag and component - at this point you can safely take the
> component out of the bag, AND safely put that component down on some
> conductive surface PROVIDED you bonded yourself to said surface by
> touching it first with your free hand, and so on.  Hand-over-hand
> bonding.  For those people whose brain cannot be trained to do this
> automatically - buy a bonding strap with a high-value resistor in it.
>
> S
>
>
>
> ------------------------------
>
> Message: 3
> Date: Tue, 11 Apr 2017 14:21:46 -0700
> From: Richard Solomon <dickw1ksz at gmail.com>
> To: Amplifiers <Amps at contesting.com>
> Subject: [Amps] Flex Amp Ad
> Message-ID:
> 	<CAC5FBO_uukB2QmQEkNC10JJgBJw-UdcZapX0FEQdu3zJY9tpUw at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> I know I am a certified "Geezer",
> but in perusing the ad for the new
> Flex Amp I saw the RF Output
> Connectors called out as SO-249 ??
>
> A typo ??
>
> Some new connector ??
>
> 73, Dick, W1KSZ
>
>
> ------------------------------
>
> Message: 4
> Date: Tue, 11 Apr 2017 22:47:20 +0000
> From: Bill Turner <dezrat at outlook.com>
> To: Amps group <amps at contesting.com>
> Subject: Re: [Amps] blowing up CMOS
> Message-ID:
> 	<CY1PR0301MB11964C76C1D1C61BC1CC6761C0000 at CY1PR0301MB1196.namprd03.prod.outlook.com>
> 	
> Content-Type: text/plain; charset="us-ascii"
>
> ------------ ORIGINAL MESSAGE ------------(may be snipped)
>
> On Wed, 12 Apr 2017 08:38:17 +1200, Steve wrote:
>
>> at this point you can safely take the
>> component out of the bag, AND safely put that component down on some
>> conductive surface PROVIDED you bonded yourself to said surface by
>> touching it first with your free hand, and so on.  H
> REPLY:
>
> This method is better than nothing, but is still not adequate.
>
> As can be demonstrated with a static meter, your body is constantly
> generating static, even when seated by simple movement of your arm and
> legs and even by shifting a little in the seat. Because of this, you
> must be constantly grounded by a wrist strap.
>
> 73, Bill W6WRT
>
>
> ------------------------------
>
> Message: 5
> Date: Tue, 11 Apr 2017 22:55:42 +0000
> From: Bill Turner <dezrat at outlook.com>
> To: Amps group <amps at contesting.com>
> Subject: Re: [Amps] blowing up CMOS
> Message-ID:
> 	<CY1PR0301MB1196027E65D2CC8B8C86910DC0000 at CY1PR0301MB1196.namprd03.prod.outlook.com>
> 	
> Content-Type: text/plain; charset="us-ascii"
>
> ------------ ORIGINAL MESSAGE ------------(may be snipped)
>
> On Tue, 11 Apr 2017 22:47:20 +0000, someone wrote:
>
>> AND safely put that component down on some
>>> conductive surface PROVIDED you bonded yourself to said surface by
>>> touching it first with your free hand, and so on.  H
> REPLY:
>
> The conductive surface must be designed to SLOWLY dissipate static. A
> metal surface is NOT safe because it dissipates static instantly and
> that will cause just the very damage you are trying to prevent.
>
> The only safe work surface is a properly grounded anti-static mat.
>
> 73, Bill W6WRT
>
>
> ------------------------------
>
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> ------------------------------
>
> End of Amps Digest, Vol 172, Issue 20
> *************************************