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Subject:
From:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Joyce Koo <[log in to unmask]>
Date:
Fri, 15 May 2009 15:50:20 -0400
Content-Type:
text/plain
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text/plain (340 lines)
Oh, my.  Have you see your sweater sparkling during the dry season?  It is sure to be an insulator.  Are you in the warm place with >60% rh all the time?  Take inge's word.  It really hurt when you get zaped. When the charge jump from sweater to your arm via air.  
--------------------------
Sent using BlackBerry


----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Fri May 15 12:41:45 2009
Subject: Re: [TN] Bare PCB Packaging Requirements

Inge,

You Wrote:
  " You claim that a capacitor can't generate current."

Why did you make up this statement about what I said?


Insulators do not conduct or transport charge and charge transfer is
required to damage a junction. 

 So, how can a insulator touch a part and damage a junction? That is what I
am asking.


 Don't bother with talks about clouds and charged caps being discharged into
junctions, these are all high current events. 

 Stop making up stories about what I said.

Bob Kondner



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Friday, May 15, 2009 10:38 AM
To: [log in to unmask]
Subject: Re: [TN] Bare PCB Packaging Requirements

OK Bob, let's see now. I've analyzed a number of semiconductors years back, 
when the gate protection wasn't as good as today. We simulated ESD 
discharges for comparison and found likewise 10-50 nanometer holes and 
channels in the semi junctions. We used even FIB to be sure.  ESD damage is 
caused by as small charges as what a 10 pF capacitor can generate. It's the 
nanosecond rise time currents that kill the gates. A SLOW discharge does not

harm any semiconductor. You claim that a capacitor can't generate current. 
Do me a favor,  charge a power supply 100uF/400V cap and put left hand index

finger on plus and right hand ditto on minus and tell me that there was no 
current. And when the clouds above you send a flash from 3 kilometers height

down to ground (in reality the opposite direction) you mean there was no 
current. The scientists talk about Mega amperes. Again, your charged PE bag 
is a very small capacitor. Everything in this world got a potential. If two 
bodies, of any kind, near each other, and they have a potential difference, 
the laws of nature orders an equalization. And that cannot take place 
without exchange of potential carriers, i.e. electrons.  Volt times current 
is energy. A bang is caused by something moving the air violently = a wave. 
Now, when you pulled off your 500 dollar golf club pullover and heard a 
'sssprriitchhh' that was a wave caused by energy in some form. Could it be 
volt x ampere?  Or volts alone with no current? What do you say? Moreover, 
can a electrostatic field exist without a charge?

Inge

PS. It's interesting that Mr Volta 'invented' the Volt and Mr Ampere the 
current. How could Ampere find amperes without volts.....he-he


----- Original Message ----- 
From: "Robert Kondner" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, May 15, 2009 3:53 PM
Subject: Re: [TN] Bare PCB Packaging Requirements


> Inge,
>
>  I absolutely agree that you can generate a 10KV+ static field with a
> simple piece of plastic.
>
>  If you are going to damage a semiconductor junction you need power, volts
> x amps.
>
>  If you touch a piece of plastic that has a 10KV field because of
> mechanical action do you get a spark? (ESD event.)
>
>  Try it, the answer is no. There is no current flow. Actually there are a
> couple of electrons that will flow but the total charge is zero for
> practical purpose.
>
>  The ESD meter you mention is telling you about electrostatic field. In 
> the
> presences of charged conductive bodies (like people) this is a good
> indication of a ESD possibility.
>
>  Volts along does nothing, you need current and volts to damage a 
> junction.
>
>  Why do so many people not believe in H Field like they believe in E 
> field?
>
> Bob Kondner
>
>
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
> Sent: Friday, May 15, 2009 3:18 AM
> To: [log in to unmask]
> Subject: Re: [TN] Bare PCB Packaging Requirements
>
> Dear Bob,
> don't you need read a little about ESD basics? If you remove electrons 
> from
> an insulator (plastic comb, acrylic clothings, cat etc) by rubbing it, the
> loss of electrons will make the insulator positive. Or you may get a 
> charge
> in the insulator by means of outer electric fields, that can move 
> electrons
> in the insulator in a way that you get a potential difference. Pulling a
> plastic comb through dry hair (if you get any)can charge your comb up to a
> thousand volts. Pulling off your acrylic pullover can generate 10,000 
> Volts!
> However, you are right in a way, the PE bag is not dangerous IF THE
> SURROUNDING ALWAYS GOT THE SAME POTENTIAL. But that is seldom the case. 
> So,
> do this for me. Get a PE bag, wave it in the air (won't work if you have a
> high RH or ionizers)and keep it close to your ESD charge meter and see 
> what
> happens. I'm afraid you will be bombarded with more about this topic.
> Good Luck
> Inge
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
> Sent: torsdag 14 maj 2009 22:58
> To: [log in to unmask]
> Subject: Re: [TN] Bare PCB Packaging Requirements
>
> Richard,
>
> Your wrote:
> "Non-ESD polyethylene bags are notorious ESD generators. I wouldn't want
> them in my factory."
>
>
>  You will NEVER get a ESD event from polyethylene because it is an
> insulator, right?
>
>  However I see lots of ESD events with grounded metal objects. Since UL
> requires metal machines to be grounded I guess you don't want any metal
> machines in your factory?
>
> What is going on here?
>
> Bob Kondner
>
>
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
> Sent: Thursday, May 14, 2009 3:12 PM
> To: [log in to unmask]
> Subject: Re: [TN] Bare PCB Packaging Requirements
>
> 1. The same moisture barrier bags that are ESD-safe Faraday bags also work
> well as moisture barrier bags for shipping and storing PWBs. These Faraday
> bags often work well for storage of the CCA during assembly. Why use two
> different types of bags if one fits the bill? Non-ESD polyethylene bags 
> are
> notorious ESD generators. I wouldn't want them in my factory.
>
> 2. Many CEMs and OEMs have requirements for the PWBs to be shipped in 
> MBBs,
> in order to prevent against surface finish oxidation in the case of IAg,
> ISn, HASL and FTL finishes. Some invoke a requirement such as IPC 4552 or
> 4553 in order to ensure the boards are dry and hermetically sealed.
>
> 3. All PWBs absorb moisture from the air. Having the boards sealed 
> prevents
> excess moisture ingress, in some cases if the boards are shipped in sealed
> bags with desiccant, the user may not need to pre-bake if they are able to
> successfully perform Kanban pull from the fabricator within a short time
> frame. This, of course, requires qualification and validation of the 
> process
> and procedures.
>
> So, if a bag is required, use one from start to finish that meets multiple
> requirements.
>
> I assume you understand why moisture within the PWB is not a desirable
> condition.
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of John Parsons
> Sent: Thursday, May 14, 2009 1:37 PM
> To: [log in to unmask]
> Subject: [TN] Bare PCB Packaging Requirements
>
> Tell us, how many CEM's out there are demanding that bare PCB's be 
> received
> in vacuum sealed moisture barrier anti-static bags.  If so, what is your
> reasoning?  Just to be clear my focus here is "anti-static" not the 
> moisture
> barrier properties of the packaging.
>
>
>
> Regards
>
>
>
> John Parsons
>
>
>
>
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