[PCB_FORUM] Re: micro vias and blind vias
- From: sjchar3@xxxxxxxxxxxx
- To: icu-pcb-forum@xxxxxxxxxxxxx
- Date: Wed, 15 Feb 2006 16:25:32 -0500
Thanks Richard, I'll be talking to them soon and thanks for the IPC reference
book. Going to see boss about some money.
-----Original Message-----
From: richard moffat <richard.moffat@xxxxxxxxxxxxxxxxxxx>
To: icu-pcb-forum@xxxxxxxxxxxxx
Sent: Thu, 16 Feb 2006 09:43:20 +1300
Subject: [PCB_FORUM] Re: micro vias and blind vias
Hello Sam
I misread your original email. I thought you were looking for good materials,
ie. what type of prepregs and cores to use. (A recent excercise we went
through for isolation requirements.)
Many places consider a microvia <= to 8mils, 8mil being the smallest practical
mechanical drill.
If you get your company to shell out for IPC-2226, it's a good reference with
really good graphics. As mentioned, Happy Holden puts out good articles as
well.
I'd still talk to your fab house though, just to confirm their capabilities.
Once you have the stackup designed, have them approve it before serious routing.
Cheers,
Richard
>>> jwages@xxxxxxxxx 16/02/2006 4:01 a.m. >>>
Last time I used blind laser vias, I ran them from top to n-1 and n-2.
(Top to 2nd lyr-pwr plane & 3rd lyr-gnd plane) and also from bottom
layer to the same bottom minus 1 and minus 2 layers, which were also
power and gnd planes. The N-1 via was a 4 mil laser drill, and the N-2
was an 8 mil drill. The hole is actually V shaped and that's what the
fabricator wants for best connectivity. I did this with Sanmina-SCI
fabricating the boards, but I think this is pretty standard.
The main thing you want to remember is to use the filmmasktop and
filmmaskbottom layers in your padstack to provide a visual reference to
which via is which. For example, I used a small square shape for the N-1
and a small triangle for the N-2 vias. It is very easy to confuse which
via is which if you don't do this.
Good luck
Jim S. Wages / SR. PCB Layout Designer:
Cary, NC - (919) 466-1596
-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of
SjChar3@xxxxxxxxxxxx
Sent: Wednesday, February 15, 2006 9:54 AM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: micro vias and blind vias
Thanks Richard, we are planning on doing a board with a .5mm bga. Since
i have never dealt with blind or micro vias i thought i could read a
little before I start asking questions to our board house. I read a
little last night and the definition I get for a micro via is a via less
than 5 mils drill. True?
Blind via i know is a via that can go into a internal layer and make a
connection. My question is "Do I create via as usual and make a pad on
L02 and top layer and call out that via where ever I may need that
particular via? Do i need to be consistent with layer names? I use L02,
L02, L04... but the other cad person uses Top, Ground, Power, Bottom.
When he tries to use th vias i created will it work on his board? These
are beginner questions and i don't know if a board house will answer
these types of questions. They'll probably point me to the cadence user
group. I best check out the suggested website and better i learn more.
Anyone want to send me a pad stack?
Thanks Sam
"richard moffat" <richard.moffat@xxxxxxxxxxxxxxxxxxx> wrote:
>Sam
>
>Different vendors will be able to cope with different materials. You
really need to contact the vendor to see what prepregs their laser (or
whatever) can punch through for blind vias, and what aspect ratios they
can do with the technology they have on site.
>
>Richard
>
>
>
>>>> SjChar3@xxxxxxxxxxxx 15/02/2006 9:10 a.m. >>>
>
>Group: Looking for reading material for micro vias and using blind
vias. Can anyone recommend good sites.
>Thanks
>Sam
>
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