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July 2009

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Subject:
From:
Vladimir Igoshev <[log in to unmask]>
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Date:
Sun, 5 Jul 2009 18:38:29 +0000
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I think I'm going to join you in kind :-). It's a Campary time :-)



Vladimir

SENTEC

11 Canadian Road, Unit 7.

Scarborough, ON M1R 5G1

Tel: (416) 899-1882

Fax: (905) 882-8812

www.sentec.ca





-----Original Message-----

From: Inge <[log in to unmask]>



Date:         Sun, 5 Jul 2009 20:06:04 

To: <[log in to unmask]>

Subject: Re: [TN] Weird solder joints





Vlad - Joyce : 3 - 1

.....aaaahh....wife came with a drink...Famous Grouse+Martini+Dubonnet + 

ice......see yo 2morrou ..

Inge





----- Original Message ----- 

From: "Vladimir Igoshev" <[log in to unmask]>

To: <[log in to unmask]>

Sent: Sunday, July 05, 2009 6:51 PM

Subject: Re: [TN] Weird solder joints





> Joyce,

>

> First of all there is no "free" Ag in SACs with less than 3.5 Ag and 

> secondly it is impossible to see ANY segregation at grain boundaries with 

> the techniques commonly used in the industry. Thirdly, I'm not aware of 

> any techniques which would allow segregation exclusively at triple 

> junction (and in essence it's just a dot in 2D !!!!).

>

> Sunday :-)

>

> Vladimir

> SENTEC

> 11 Canadian Road, Unit 7.

> Scarborough, ON M1R 5G1

> Tel: (416) 899-1882

> Fax: (905) 882-8812

> www.sentec.ca

>

>

> -----Original Message-----

> From: Joyce Koo <[log in to unmask]>

>

> Date:         Sun, 5 Jul 2009 12:12:46

> To: <[log in to unmask]>

> Subject: Re: [TN] Weird solder joints

>

>

> Too much brain on grain?  SAC has ag sagrigation in grain boundary and 

> some ppc paticles of minor additives, assume add by vendor as grain growth 

> inhibitor, in triple junction.  To assessing grain structure is possible 

> in some of the SAC I believe.  Silly brain, go back to holiday mode.  Left 

> side is shutting down.  Zzzz.

> --------------------------

> Sent using BlackBerry

>

>

> ----- Original Message -----

> From: TechNet <[log in to unmask]>

> To: [log in to unmask] <[log in to unmask]>

> Sent: Sun Jul 05 11:47:18 2009

> Subject: Re: [TN] Weird solder joints

>

> Vladimir, Gaby, Inge, Mike - People!!!  This is Sunday!!  Are we trying to

> start the work week a day earlier??

>

> It is really close for Ingemar already!

>

>

> Maybe this is the weekend troubleshooting crew!  Kind of like the weekend 

> TV

> anchor team...

>

>   I can just imagine how Dewey's response to 'grains' might be related to

> beverages.

>

>

> Gaby - At least it appears that you have gotten a fair amount of 

> information

> already this weekend - making your Monday a bit more efficient.

>

> I enjoyed the calm winds and 68-70°F temps to go flying this morning. 

> From

> the micro to the macro.  A pleasant change in perspective

>

> Enjoy the remainder of your Sunday

>

> Steve C

>

> -----Original Message-----

> From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev

> Sent: Sunday, July 05, 2009 10:20 AM

> To: [log in to unmask]

> Subject: Re: [TN] Weird solder joints

>

> Thank you inge,

>

> Even though I believe I know a few things, a person can not know 

> everything

> :-). That is why I asked the question.

>

> Honestly, I'm still almost confused every time I hear someone referring to

> the grain structure in solder joints. I know  it's pain in the neck to

> reveal the real grain structure in solders (and even more so in Pb-free

> world, than in the eutectic one), meaning it's not a practical thing to 

> do.

>

> Therefore  I always ask the same question: "what do you mean by "grain

> structure" and almost always it turns out to be the phase (not grain)

> structure, which makes much more sense to me.

>

> Honestly, I'm not even sure whether the grain structure (which would 

> mainly

> their size inside the individual phase) plays a role in reliability of

> solder joints.

>

> In fact, a few years ago we deliberately tried to grow Sn grains in one of

> the SAC alloys and ended up with nothing - the original grain size (a few

> microns) never changed. I thought it was very interesting.

>

> Regards,

>

> Vladimir

> SENTEC

> SENTEC

> 11 Canadian Road, Unit 7.

> Scarborough, ON M1R 5G1

> Tel: (416) 899-1882

> Fax: (905) 882-8812

> www.sentec.ca

>

>

> -----Original Message-----

> From: Inge <[log in to unmask]>

>

> Date:         Sun, 5 Jul 2009 10:42:49

> To: <[log in to unmask]>

> Subject: Re: [TN] Weird solder joints

>

>

> Vlad,

>

> 1. the alloy members have solidified evenly all through the ball

> 2. the distribution of phases are even

> 3. the grains are fine

>

> you'd know it well, being a guru yaself

>

> Inge

>

>

> ----- Original Message ----- 

> From: <[log in to unmask]>

> To: "TechNet E-Mail Forum" <[log in to unmask]>; "Inge"

> <[log in to unmask]>

> Sent: Saturday, July 04, 2009 11:06 PM

> Subject: Re: [TN] Weird solder joints

>

>

>> Inge,

>>

>> Could you elaborate on what you mean by "good grain structure"?

>>

>> Thanks,

>>

>> Vladimir

>> SENTEC

>> SENTEC

>> 11 Canadian Road, Unit 7.

>> Scarborough, ON M1R 5G1

>> Tel: (416) 899-1882

>> Fax: (905) 882-8812

>> www.sentec.ca

>>

>>

>> -----Original Message-----

>> From: Inge <[log in to unmask]>

>>

>> Date:         Sat, 4 Jul 2009 20:48:31

>> To: <[log in to unmask]>

>> Subject: Re: [TN] Weird solder joints

>>

>>

>> Gaby,

>> solder joints are often expected to be perfect and according to the 

>> school

>> book, but in the real world they are more or less imperfekt.

>> Plus:

>> good geomtry

>> good wetting

>> good surface formation

>> no big dendrites

>> no big voids

>> good nickel barrier

>> good grain structure

>>

>> Minus

>> flux inclusions wich have not have time enough to withdraw to the 

>> surface.

>> I think you have got a too dry paste. I've seen similar solder joints and

>> we had no problems. If we had, some boards ought to show up after years

>> of operation.

>>

>> I can't see any reason to panic, your solder joints are rather normal. Do

>> this: take the polished

>> crossection samples and put then in a jar with a flux remover. Place the

>> jar

>> in a water filled ultrasonic tank and let go for a minute. If the 'dark'

>> streaks disappear, it's certainly flux.

>>

>> It's  good for all to know how strong and longlasting solder joints can 

>> be

>> despite numerous 'anomalies' as brother Creswick call them.I've tested

>> solder joints with up to 50% voids...and they have been nearly as good as

>> normal ones. Because the metallurgical properties have been good.

>>

>> Finally, judging solder joints from light microscope images demands a 

>> very

>> experienced eye. If I were you , i.e. young and sweet and uncertain , I'd

>> fine polish the samples, etch in a weak solution for a minute and have

>> them

>> placed in a SEM. Does not take many minutes to get a safer platform for

>> determination.

>>

>>

>> Inge

>>

>>

>>

>> ----- Original Message ----- 

>> From: "Gabriela" <[log in to unmask]>

>> To: <[log in to unmask]>

>> Sent: Saturday, July 04, 2009 9:54 AM

>> Subject: [TN] Weird solder joints

>>

>>

>>> Dear all,

>>> By cross sectioning BGA solder joints on a failed assembly, I found that

>>> the

>>> suspected joints are not uniform and that they contain unusual 

>>> separation

>>> areas.

>>>

>>> I suspect mixed assembly and/or bad reflow profile.

>>>

>>> Steve was so kind and enabled me to send the links.

>>> Please may I have your opinion?

>>> http://stevezeva.homestead.com/files/small.jpg

>>>

>>>

>>>

>>> <http://stevezeva.homestead.com/files/small1.jpg>

>>> http://stevezeva.homestead.com/files/small1.jpg

>>>

>>>

>>>

>>> <http://stevezeva.homestead.com/files/small2.jpg>

>>> http://stevezeva.homestead.com/files/small2.jpg

>>>

>>> http://stevezeva.homestead.com/files/small3.jpg

>>>

>>> <http://stevezeva.homestead.com/files/small4.jpg>

>>> http://stevezeva.homestead.com/files/small4.jpg

>>>

>>>

>>>

>>>

>>> Gaby

>>>

>>>

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