The VIP process is not so simple (materials, filling, curing, flatness
etc.) not all the PCBs shops know how to do it right, so in order not to
limit ourselves and also costs aspects (beside the reliability), I
recommend up to 0.5 mm pitch to design the vias out of the bumps pads.
Best Regards
Reuven ROKAH
Lee Parker
<lee.parker@THEE To: [log in to unmask]
CMG.COM> cc:
Sent by: TechNet Subject: Re: [TN] VIA in Pad
<[log in to unmask]
>
30/06/2004 04:48
Please respond
to "TechNet
E-Mail Forum.";
Please respond
to Lee Parker
I agree.
Many of these materials expand during the curing process and completely
fill the barrel while releasing all volatiles. Consequently after
leveling and plating they become benign.
Lee
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Mcmaster, Michael
Sent: Tuesday, June 29, 2004 8:33 PM
To: [log in to unmask]
Subject: Re: [TN] VIA in Pad
Reuven - I disagree with your assertion that VIP is not 100% safe. With
proper selection of via fill material and a reasonable hole aspect
ratio,
you should have neither solderability or void issues.
Mike McMaster
RF Product Engineer
Merix Corporation
503-992-4263
> ----------
> From: Reuven ROKAH[SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;[log in to unmask]
> Sent: Monday, June 28, 2004 10:08 PM
> To: [log in to unmask]
> Subject: Re: [TN] VIA in Pad
>
> I recommend to try as a first priority to layout the via out of the
BGA
> pad
> (bump) to adjacent special micro via hole pad.
> Up to 0.5 mils pitch it can be done.
> The filling VIP is not 100% safe (solderability and voids aspects).
>
>
> Best Regards
>
> Reuven ROKAH
>
>
>
>
> "Macko, Joe @
> IEC" <joe.macko To:
[log in to unmask]
> Sent by: TechNet cc:
> <[log in to unmask] Subject: Re: [TN] VIA
in
> Pad
> >
>
>
> 28/06/2004 17:35
> Please respond
> to "TechNet
> E-Mail Forum.";
> Please respond
> to "Macko, Joe @
> IEC"
>
>
>
>
>
> Tom,
>
> My experience has been that their generally a direct correlation
between
> voiding and VIP locations. Of course, the size of VIP has a direct
> bearing
> on the potential size of the void in the solder ball ..... Our
current
> policy is to fill all VIPs to preclude any voiding problems or
> insufficient
> solder conditions in leaded parts.
>
> I would sensitize your customer to the potential for voiding which may
not
> meet IPC guidelines, and the need for rework with VIPs for leaded
parts.
> Good luck.
>
> joe
>
> -----Original Message-----
> From: Tom Parkinson [mailto:[log in to unmask]]
> Sent: Friday, June 25, 2004 8:20 AM
> To: [log in to unmask]
> Subject: [TN] VIA in Pad
>
>
> We're a CM. One of our customers is asking us to build a board
assembly
> that will be using BGAs with VIAs in pads. They are in the design
stages
> at
> this point, and we have some concerns with having a Via in the middle
of a
> BGA pad. Anyone have suggestions and/or experience with this??
>
>
>
> Thanks
>
>
>
>
>
> Tom Parkinson - Quality System Manager - CIT
>
> WinTronics, Inc.
>
> Ph: 724-981-5770 Ext. 235
>
> Fax: 724-981-1772
>
>
>
>
>
>
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