Chad,

Is using blind Microvias acceptable, since their cavity is so small it would
rob a very small % of the solder? (I know this is expensive, but besides
this factor).

R. Kubes
Honeywell DAS Albq

> ----------
> From:         Thibodeau, Chad[SMTP:[log in to unmask]]
> Sent:         Monday, October 05, 1998 11:41 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] Via's under BGA's
>
> Bridget,
>
> There was an excellent paper written by Paul Mescher of Amkor Anam
> addressign "...Surface Mount Assembly of Amkor/Anam BGA Packages".  In
> this
> paper Paul describes the importance of PTH isolation (via isolation) and
> to
> paraphrase him: "No matter what shape or definition technique is used for
> the mounting pad, the isolation of the PTH from the mounting pad is an
> important feature.  If the PTH is contained within the mounting pad,
> solder
> can and will wick down the PTH.  The amount of solder that wicks depends
> on
> many factors, including PTH finish and coating variations.  Because of
> this,
> the results are somewhat unpredictable.  Some solder joints may be
> unaffected, while others will be starved to the point of creating opens.
> The worst result is a partially starved joint with severely reduced cross
> section.  This joint can have significantly lower fatigue life and result
> in
> early system failure.  Because the quality of the solder joint is
> guaranteed
> by control, rather than inspection, designs/processes that result in
> random
> distributions are generally considered unacceptable, and the PTH-in-pad
> design is not recommended."
>
> If you require additional information you may want to talk with Paul
> himself.  I do not have his number, but he is located in Chandler, AZ.
>
> Chad Thibodeau
> EF Data
> Component Engineer
> 602 333-2138 Phone
> 602 921-9012 Fax
> [log in to unmask]
>
> ################################################################
> TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
> ################################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in the body:
> To subscribe:   SUBSCRIBE TechNet <your full name>
> To unsubscribe:   SIGNOFF TechNet
> ################################################################
> Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
> section for additional information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or
> 847-509-9700 ext.312
> ################################################################
>

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################