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November 2006

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Subject:
Re: One solder Ball Not Connected on a No Connect Pad After Rework
From:
Gabriela Bogdan <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Gabriela Bogdan <[log in to unmask]>
Date:
Fri, 17 Nov 2006 19:39:07 +0300
Content-Type:
text/plain
Parts/Attachments:
text/plain (139 lines) 
Vladimir,
You are right, it is just that I had this problem too and in the end the
conductors had cracks and the pads were really lifted-(not ground pads
solder mask defined)..I could see the cracks only by X-ray...
Gaby
----- Original Message -----
From: "Vladimir Igoshev" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, November 17, 2006 7:06 PM
Subject: Re: [TN] One solder Ball Not Connected on a No Connect Pad After
Rework


> Hi Gaby,
>
> It doesn't have to be cracked, particularly if the pad in question is
> non- SMD.
>
> Regards,
>
> Vladimir
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Gabriela Bogdan
> Sent: Friday, November 17, 2006 10:56 AM
> To: [log in to unmask]
> Subject: Re: [TN] One solder Ball Not Connected on a No Connect Pad
> After Rework
>
> If the pad comes off it is because there is a crack between the pad and
> the
> base material, and no conductor is there to prevent it from coming off.
> I
> would suspect that if you do a cross section of active pads in the same
> area
> you have a fair chance to see such cracks unde the pads, and even lifted
> pads.
> You intend to  replace the BGA on this area. Are you sure that the new
> connections will be as good as new?
> Gaby
> ----- Original Message -----
> From: "bob wettermann" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Friday, November 17, 2006 6:10 PM
> Subject: [TN] One solder Ball Not Connected on a No Connect Pad After
> Rework
>
>
>> This question to the group is about expected solder joint strength on
> a
>> BGA.
>>
>>  The BGA in question is a 8 x 8mm plastic package  BGA using a LF
> SAC305
>> soldering process. It has 64  x 0.018" balls holding it to  the PCB.
>>
>>  When removing this device for rework 3-4% of the time one of the
> corner
>> NO CONNECT pads comes off.
>>
>>  The question is if we do nothing upon replacement of  a new device
> to
>> the damaged pad will it really make a difference ??? We are arguing
> that
>> the holding strength of the reworked device would be approximately
> the
>> same because the change in overall surface area is marginally
> impacted.
>>
>>
>>  Thanks
>>
>>  Bob Wettermann
>>
>>
>> Bob Wettermann
>>
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