Steve,
I've manipulated the photo a little. You can see quite clearly, that this is
a common blowhole.
One need not howl about a blow hole, as long as it does'nt foal a whole
foxhole.
Sending the picture offline to you for the others to see.
Inge
----- Original Message -----
From: "Inge" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, July 05, 2009 11:08 AM
Subject: Re: [TN] Weird solder joints
> George,
> thanks for the nice comment.
> Now, Gaby, I've studied the new images you sent to me, and I'm rather sure
> about what you've got: blow holes. They occur when built-in humidity or
> volatiles have no other way to escape, than by making a tunnel. The vapour
> pressure becomes that high. Again, don't bother too much in your case.
> Read what this guy says (think it was Wassink, but I'm not sure):
>
> ".........Voids (blow holes) are of particular concern with the small
> rigid joints associated with BGAs, where the solder ball itself is the
> joint. Banks studied the effect of voiding on BGA reliability, and
> reported that voids up to 24% of the volume caused no negative effect on
> reliability. In fact, joints with voids had 16% better reliability than
> those without voids. The cracks that occurred were in the same places
> whether or not the joints had voids. ...."
>
> Good Luck
>
> Inge
>
>
>
> ----- Original Message -----
> From: "Wenger, George M." <[log in to unmask]>
> To: "TechNet E-Mail Forum" <[log in to unmask]>; "Inge"
> <[log in to unmask]>
> Sent: Saturday, July 04, 2009 10:13 PM
> Subject: RE: [TN] Weird solder joints
>
>
> Gaby,
>
> Ingemar and Steve have provided good advice.
>
> Ingemar,
>
> Your vast experience with solder assembly and material issues still
> manages to amaze me. The only thing I would add is that Steve's idea of
> an inclusion in the solder paste may also be the cause. I've looked at
> the changing the brightness and contrast of the images and it does
> appear that at least on the small2.jpg the dark area does look like a
> fibrous inclusion that actually sticks out a short distance from the
> solder ball into the cross section potting compound.
>
> Regards,
>
> George
>
> George M. Wenger
>
> Andrew Wireless Solutions
>
> Senior Principal FMA / Reliability Engineer
>
> 40 Technology Drive, Warren, NJ 07059
>
> (908) 546-4531 [Office] (732) 309-8964 [Mobile]
>
> [log in to unmask]
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
> Sent: Saturday, July 04, 2009 2:49 PM
> 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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