thanks. I thought product qual is same as process qual...jk ;-)
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of Tegehall Per-Erik
>Sent: Thursday, October 03, 2002 9:09 AM
>To: [log in to unmask]
>Subject: Re: [TN] Ionograph measurements
>
>
>Joyce,
>
>As I understood the orignal question, the Ionograph measurements were used
>for a sort of product (assembly) qualification per J-STD-001C, i.e. neither
>process development nor process control.
>
>Per-Erik
>
>-----Ursprungligt meddelande-----
>Från: joyce [mailto:[log in to unmask]]
>Skickat: den 2 oktober 2002 14:19
>Till: TechNet E-Mail Forum.; Tegehall Per-Erik
>Ämne: RE: [TN] Ionograph measurements
>
>
>guys, I am bit confused here. Are we talking about process development or
>process control at assembly level?
>(1) all the cleanliness establishment shall be done at development stage.
>Ionograph is not a good tool. Liquid chromatography might be the
>better way
>to go to define what is the compatibility problem and what kind of
>contamination is on the board. If you get the right personnel,
>you might be
>able to pin point what is the root cause if you exceeding the spec.
>(2) Ionograph is good for process control after you defined your "process".
>It give a lump sum of ionic reading without differentiate where it
>come from
>and what it is. If you got 6 sigma control of everything, you should not
>see any difference between your process development stage and control. If
>you change vendor, as long as you know what to look for, you should be fine
>after vendor qual.
>(3) sure you can use Ionograph machine as cleaner (did that
>before)...provide you know what are you doing and have enough money to
>replace some of the parts in the Ionograph machine...(depend upon who is
>going to do the replacement, if it is you, you most likely will have second
>thought).
>In theory, if the process development were done properly, the chances for
>the exceeding spec is very very slim. Normally, when it is start to drift
>towards the limit, someone should start walk on the floor to play
>detectives. However, that does not give you any glory status of "problem
>solver" or "team player".
>
>jk
>
>>-----Original Message-----
>>From: TechNet [mailto:[log in to unmask]]On Behalf Of Tegehall Per-Erik
>>Sent: Tuesday, October 01, 2002 2:56 AM
>>To: [log in to unmask]
>>Subject: Re: [TN] Ionograph measurements
>>
>>
>>Even if you could find a method to scientifically measure
>cleanliness of an
>>assembly (which I doubt will ever happen since flux residues are absorbed
>>into the epoxy resin) you would also need to be able to tell how the
>>concentration of the various contaminants varies over the surface of the
>>assembly in order to assess the impact on reliability. This means that you
>>also must be able to transform contamination levels into reliability
>>figures. You must then know which of the contaminants that are hygroscopic
>>and which are hydrophobic, which are ionic and which are
>>non-ionic, but also
>>which contaminants that cause synergistic effects when mixed.
>>
>>Therefore, I think, a scintific approach for verifying quality ought to
>>focus on methods for assessing the impact on reliability instead
>of methods
>>for measuring the cleanliness. Surface Insulation Resistance (SIR)
>>measurements is such a method (described in Appendix B in J-STD-001C) but,
>>as it is used today, its scintific base including acceptance criterion is
>>not what it ought to be.
>>
>>Per-Erik
>>
>>-----Ursprungligt meddelande-----
>>Från: [log in to unmask] [mailto:[log in to unmask]]
>>Skickat: den 1 oktober 2002 01:50
>>Till: TechNet E-Mail Forum.; Tegehall Per-Erik
>>Kopia: [log in to unmask]
>>Ämne: Re: [TN] Ionograph measurements
>>
>>
>>
>>How does one, scientifically, measure cleanliness of an assembly? It's
>>always struck me that if your cleanliness measuring equipment can extract
>>enough salts, etc., to measure something, then your cleaning equipment
>>isn't good enough, and maybe you should be cleaning with your measuring
>>equipment instead.
>>
>>And how to tell that you're not extracting some vital ingredient of the
>>board material and not just surface contaminaton, short of using some SEM
>>and checking out the molecules?
>>
>>Just a thought (or not) (where have I heard that before?)
>>
>>Peter
>>
>>
>>
>>Tegehall Per-Erik <[log in to unmask]> 30/09/2002 10:04 PM
>>Sent by: TechNet <[log in to unmask]>
>>
>>Please respond to "TechNet E-Mail Forum."; Please respond to Tegehall
>>Per-Erik
>>
>>
>> To: [log in to unmask]
>>
>> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
>>
>> Subject: Re: [TN] Ionograph measurements
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>Daan,
>>
>>In a note to section 8.3.6 in I-STD-001C, it is written that "In comparing
>>the sensitivity between methods, the solvent used to extract the residue,
>>the method used to present the solvent to the assembly and the method of
>>detecting the residue should all be considered. " I interpret that as you
>>are allowed to and should do the correction. But if you use correction
>>values, the figures given in the MIL standard are only valid for
>the models
>>of cleanliness equipment that were used at that time. I guess Alpha
>>Ionograph 500M is a later model, which means that it should have a
>>different
>>correction figure (probably higher since it likely has better cleaning
>>efficiency).
>>
>>However, the use of equivalence factors has no scientific base. But on the
>>other hand, neither has the method for cleanliness measurement. It
>>shouldn´t
>>be used as proof of the cleanliness of an assembly since it is no proof of
>>assembly reliability. It is a good tool for process control, i.e. to
>>control
>>that the cleanliness of assemblies manufactured in certain line does not
>>change with time. In my opinion, its use should be limited to that.
>>
>>Regards
>>Per-Erik
>>
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