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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, 30 May 2014 19:47:32 +0000
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text/plain
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text/plain (1 lines)
Underfill - if not cure properly, you have extractable ionics.  As for the formulation developed, you might want to add a bit more activator, that is normally acid based... if you add too much - some of the bad chemist do, you got problem.  If you add too little, the material will not last for the long shelf life (provide it is stable) you want - the activator usually is the 1st thing degraded in liquid underfill during storage.  In addition, the filler surface, depend upon where you get them, it might have acidity value (surface of the filler - usually SiO2 spheres).  Of cause, the acidity depend upon the supplier, and the amount of surface you get - size and amount of filler distribution... even you get the same underfill polymer formula, that does not grantee you are trouble free if you change to a cheap vendor for the filler... (not mention the alpha particle counts you need to worry about - another story).  Work with reputable vendor with a lot of experience is a good start - make sure it is a mature formulation... I like cutting edge technology, but for underfill, I go with the "tradition" (older the chemist, the better - no offence to the younger generation).  My 2 cents.  

Joyce Koo
Senior MIL Specialist
Materials Interconnect Lab
Office: +1 (519) 888-7465 x 79945
BlackBerry: +1 (226) 220-4760





-----Original Message-----
From: GRIVON Arnaud [mailto:[log in to unmask]] 
Sent: Friday, May 30, 2014 2:15 PM
To: TechNet E-Mail Forum; Joyce Koo
Subject: Re: [TN] PCB Cleanliness Via Ion Chromatography Poll (informal)

Hi Joyce,

Currentky working on BGA underfilling and hence interested by your post and related statement.
Sony, but I did not catch what could offer IC with respect to underfilling...
Could you elaborate a bit?
Are you checking the underfill resin or the solder mask?
What is the issue you are trying to control (resin flow?)?
Best regards,

Arnaud Grivon
Thales Global Services
Tél. : (+33) (0) 1 70 28 23 88

Joyce Koo <[log in to unmask]> a écrit :


IC is great tool for initial qualification and development, not only for PWB, but also for underfill adhesives.  Specially for UV curable solder mask, a bit less powerful lamp (as it ages), you might risk to have problem.  IC can pin point the process step with IR (less sensitive).  As for underfill, IC sometimes is great to see if the filler surface acidity changes that may effect your curing and filler settling/flow - problematic for process.  However, there are extensive leg work you need to do at developing stage (multi-techniques, IC just one of them).

Joyce Koo
Senior MIL Specialist
Materials Interconnect Lab
Office: +1 (519) 888-7465 x 79945
BlackBerry: +1 (226) 220-4760





-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Russeau
Sent: Wednesday, May 28, 2014 9:37 AM
To: [log in to unmask]
Subject: Re: [TN] PCB Cleanliness Via Ion Chromatography Poll (informal)

Hello Brian,

See my responses to your comments below, designated by ***.

Best Regards,

Joe Russeau

----- Original Message -----
From: "Brian Ellis" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, May 28, 2014 3:12 AM
Subject: Re: [TN] PCB Cleanliness Via Ion Chromatography Poll (informal)


> Let me add a couple of eurocents worth.
>
> 1. Ion chromatography is useless for incoming board testing. Far too 
> long and far too expensive. By the time you have the results from a 
> valid sample of a batch (say 1-5%), your board will be obsolete.

*** Again, I have to disagree that the "tool" is useless for incoming board testing.  It has two very important analytical features that make it applicable.  Those two features are selectivity and sensitivity.  Now I am not saying it is a perfect tool. Like any analytical technique it has its limitations.  However, it is has a tremendous amount of capability if it is properly set-up and the user understands how to apply it AND understands the material sets he/she is evaluating.

Does it take too long?  Possibly, it depends (Doug just add that to my Mt.
Dew tab).  It depends on what too long means.  If your goal is to have an immediate answer then yes it takes too long.  I know many that utilize ROSE to test/control/track incoming board cleanliness because it is quick and gives an immediate answer, but when you ask them how they know the board is clean, I often hear silence on the other end of the phone.  On  the other hand, if your goal is to understand what is present on the surface of your board and what impacts certain ions may have on product reliability, then perhaps the time to test isn't so long.  It really boils down to your goal for testing.  Also, if all your looking for are simple anions and cations, then IC systems can churn those results out in about ten minutes (depending on your set-up).  If organics are in the sample matrix, then more time is going to be needed to evaluate them.  IC is not an immediate answer I'll grant you that, but it gives those that are trying to understand their residue picture more information about it.

As for expense, it can be expensive depending on who is doing the testing and what is being analyzed.  But keep in mind that part of the expense is paying for the expertise and knowledge.  I know that it is difficult to place a price on that, but hey if it helps someone avoid a process line from being shut down, then the expense of testing is a pittance by comparison.


>
> 2. SIR or ECM testing is useless for incoming board testing. Far too 
> long and far too expensive. By the time you have the results from a 
> valid sample of a batch (say 1-5%), your board will be obsolete.

*** Totally agree.

>
> 3. IC, SIR and ECM are qualification tests, unsuitable for incoming 
> goods testing. Because of the chemical nature of the surface finishes, 
> it is impossible to extrapolate the results obtained during 
> qualification to production conditions, because there may be slight 
> differences in the stoichiometry of the resins and their various 
> treatments in board manufacture (or even changes of laminate manufacturer) etc.
>

*** My only disagreement with your statement above is classifying IC as a qualification tool.  I would not classify it as such. Why? Because there is a lot of subjectivity between the experts in defining what is considered clean and not clean.  IPC-5704 helps some with incoming board cleanliness by setting up an industry standard that has been mutually agreed upon within committee.  However, no such standard exists for assembly cleanliness and some might be misled into thinking that IC can be used to qualify their products.  I'd say it can help in understanding the residue picture, but I wouldn't rely solely on those results to say all is good.  It provides data into one aspect of reliability.  Other testing may be required depending upon what you are qualifying.

> 4. In my considered opinion, the *ONLY* practical test for incoming 
> boards in a production environment is ICT (Ionic Contamination 
> Testing), sometimes incorrectly called the "ROSE" test for historical 
> reasons. It is fast, if rough and ready, and will detect the presence 
> of most (but not
> all) of the harmful contaminants and bad stoichiometry of resins, 
> without necessarily identifying them (some testers will give 
> indications of the causes of problems by software analysis). Don't 
> underestimate this valuable tool.

*** No comment.
>
> Brian
>
>
> On 23.05.2014 16:27, Richard Kraszewski wrote:
>> I actually sent this out on May  16th, but never got a single response.
>> Hoping that was not due to lack of interest, but rather due to the 
>> TechNet being down. Hence, I think I'll try this one more time.
>>
>> I am  hoping to run an informal " min straw poll " here.
>>
>> Questions stated  are as follows:
>>
>>
>> 1.       "Is your organization testing  incoming  PCB cleanliness  via
>> ion- chromatography?             Replies such as "YES" or "NO" will
>> suffice, but more detailed explanations are also acceptable.
>>
>>
>>
>> 2.       " If testing via IC, do you use IPC -5704 Table 4.1 limits or
>> other?                                                Replies such as "
>> IPC"  or "other"  will suffice, but more detailed explanations are 
>> also acceptable.
>>
>> What's in  it for  you?   I will summarize and post the results after a
>> few days of replies.
>>
>> Rich  Kraszewski
>> Senior Process Engineer
>> Plexus
>>
>>
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