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September 2009

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Subject:
From:
Vladimir Igoshev <[log in to unmask]>
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Date:
Thu, 17 Sep 2009 20:05:06 +0000
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Inge, solder is ductile ("soft") but it's not a "plasticine" (and Pb-free particularly). So a crack (once been formed) doesn't become blunt and it grows. All you might need is a tiny stress concentrator to create one and the thickness of solder mask doesn't matter in that situation.



Regards,



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:         Thu, 17 Sep 2009 21:43:22 

To: <[log in to unmask]>

Subject: Re: [TN] fractured SJs due to soldermask compression





Richard,

we have seen so many microcracks start at the edge of the defined 

soldermask, that we do only non-defined boards. One thing I don't 

understand: how can the small percentage of the thin soldermask cause damage 

to the much bigger area of the solder ball, especially when the solder is a 

little 'flexible' (I know W does not like the word)? It does not make sense 

to me.

/Inge





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

From: "Stadem, Richard D." <[log in to unmask]>

To: <[log in to unmask]>

Sent: Thursday, September 17, 2009 7:49 PM

Subject: Re: [TN] fractured SJs due to soldermask compression





> Werner,

> What I am trying to say is that issues of ground plane configuration will 

> probably not lead to a reliability issue directly, unless they cause 

> issues during reflow of the BGA. But if the ground pour is done using 

> soldermask-defined pads, the soldermask-defined pads can lead to premature 

> failure of the SJ. My understanding (gained from a direct question I asked 

> you in your class) was that the soldermask can constrict the solder during 

> CTE expansion and contraction. Did I not understand you correctly?

>

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

> From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*

> Sent: Thursday, September 17, 2009 12:32 PM

> To: [log in to unmask]

> Subject: Re: [TN] fractured SJs due to soldermask compression

>

>

> Hi Chris,

> First, never heard of "fractured SJs due to soldermask compression during 

> cyclic operation"—solder mask is much too soft and too thin; now, if you 

> talk encapsulants that is a different story.

> Second, "all of the other issues pale in the face of fractured SJs due to 

> soldermask compression during cyclic operation"—even if it were an issue, 

> a failure is a failure is a failure—'nough said.

> Werner

>

>

>

>

>

>

>

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

> From: Chris Ball <[log in to unmask]>

> To: [log in to unmask]

> Sent: Thu, Sep 17, 2009 1:07 pm

> Subject: [TN] fractured SJs due to soldermask compression

>

>

>

>

>

>

>

>

>

>

> Hello,

>

> Starting a new branch here.

>

> "All of the other issues pale in the face of fractured SJs due to

> soldermask compression during cyclic operation."

>

> Is this concern specifically for BGAs, or the same for any soldermask

> defined pad, even including selectively waved through-hole (PbFree)?

>

> Thanks,

> -Chris

>

>

>

>

>

>

>

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