1. Exposed copper.
2. Solder paste entrapping in cavities during miss print / cleaning.
3. Solder balls
--------------------------------------------------------------------------------------------------------------------------
Best Regards
Reuven ROKAH
Gabriela Bogdan
<gabriela@NETVISI
ON.NET.IL> To
Sent by: TechNet [log in to unmask]
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Subject
01/12/2005 05:18 Re: [TN] Plugging vias necessary?
Please respond to
TechNet E-Mail
Forum
<[log in to unmask]>
; Please respond
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Gabriela Bogdan
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Are there any reliability issues when using solder mask encroaching for OSP
boards instead of capping?
Gaby
----- Original Message -----
From: "Sherif Refaat" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, November 30, 2005 11:32 PM
Subject: Re: [TN] Plugging vias necessary?
> One way to stop the solder wicking without plugging or tenting the via
> holes is to extend the solder mask, so it would cover the via pad without
> encroaching on the via hole itself. This way there will be a wider dam of
> solder mask that should be enough to prevent the solder thieving.
>
>
> Sherif Refaat, Eng.
>
> Technology Roadmap Consultants Inc.
>
> E-mail: [log in to unmask]
>
> Tel. (514) 624 9842
>
> Fax (514) 624 0091
>
>
>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard
>> Sent: Wednesday, November 30, 2005 3:59 PM
>> To: [log in to unmask]
>> Subject: Re: [TN] Plugging vias necessary?
>>
>> Without the plug, the solder from the sphere can wet down into the
>> adjacent via to the backside of the pwb during reflow.
>> On a dogbone pattern, with one side the pad and the other side the
>> connecting via, the small soldermask dam that goes over the thinnest
>> part of the dogbone pattern is not enough to stop the solder wicking.
>> The solder will wick right under that flimsy little dam, and the via
>> will rob the solder. This is called solder thieving. The soldermask plug
>> prevents that from happening. If you ever need to rework that BGA, the
>> site prep operation nearly always makes the little soldermask dam worse,
>> and after you replace the part you get even more solder thieving, and
>> the entire rework/X-ray/test/rework cycle spins on down into a black
>> hole called scrap. One almost never sees BGAs with daisychained dogbones
>> without the soldermask plug, and that is a good thing, as Martha says.
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Black, Paul
>> Sent: Wednesday, November 30, 2005 7:50 AM
>> To: [log in to unmask]
>> Subject: [TN] Plugging vias necessary?
>>
>> Hi Everyone,
>>
>> I have a board with a 357 pin PBGA. Each pad has a short etch leading to
>> an adjacent via. Currently, the fabrication drawing calls for each via
>> to be plugged. The assembly process for this board does not contain a
>> wave solder step and the test engineer assures me that plugging the vias
>> is not necessary for vacuum during incircuit testing, so is there some
>> other reason for plugging these vias? They are plugged with soldermask,
>> and I feel like we are unnecessarily introducing potential problems into
>> the process.
>>
>> Thanks in advance for your opinions.
>>
>> Paul Black
>> Manufacturing Engineer
>> Kronos
>> [log in to unmask]
>>
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