[SI-LIST] Re: PCB thickness
- From: Hithesh <hitheshn@xxxxxxxxx>
- To: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- Date: Sat, 2 Feb 2013 14:26:17 +0530
Istvan,
Thanks for the reply.
I did ask them to increase the dielectric thickness between L3-L4 and L5-L6.
They said they cannot do it. I have no idea why they can't do it.
-Hithesh
On Sat, Feb 2, 2013 at 2:01 PM, Istvan Novak <istvan.novak@xxxxxxxxxxx>wrote:
> Hi Hithesh,
>
> Different fab houses may have access to, or may prefer to use, different
> laminates.
> With your stackup, however, there seems to be a very simple solution.
> Unless
> you use L5 and L6 for broadside coupled differential routing, you can ask
> the second
> fab house to add board thickness by increasing the L3-L4 and L5-L6
> thicknesses
> by the same amount so that the total board thickness comes closer to your
> target.
>
> Regards,
>
> Istvan Novak
> Oracle
>
>
>
>
> On 2/2/2013 12:11 AM, Hithesh wrote:
>
>> Hi,
>> It's an 8 layer board.
>> Stack up below
>> L1: Fan out/GND
>> L2: GND
>> L3: Sig
>> L4: PWR
>> L5: Sig
>> L6: Sig
>> L7: GND
>> L8: Fan out/GND
>>
>> The Cu thickness is 1oz on inner layers and 1oz finished thickness on
>> outer
>> layers.
>> The Er/dielectric is left to the fab house.
>> The board has high speed USB diff signals and DDR2 (133MHz).
>>
>> We use different Fab house for protos and production. The proto Fab house
>> did not have any difficulty achieving board thickness and our impedance
>> requirement. But the production Fab house wants to reduce PCB thickness
>> and
>> modify dielectric thickness.
>>
>> Regards
>> -Hithesh
>>
>>
>> On Sat, Feb 2, 2013 at 1:32 PM, Nobuyuki Kunito <kunito@xxxxxxxxxxx>
>> wrote:
>>
>> Hithesh,
>>>
>>> First of all, please tell us:
>>> How many layers the PCB have?
>>> Layer construction and/or stack up (the thickness of metal, dielectric
>>> material and Er of each dielectric material etc.)
>>> I am guessing that the PCB fib house may change the dielectric material..
>>>
>>> Please give us the information above first.
>>>
>>> Regards,
>>> Nobuyuki Kunito.
>>> The president of Debug Lab.
>>> http://debuglab.jp
>>> (Sorry, Japanese only now. English page will be coming soon)
>>>
>>> (2013/02/02 15:17), Hithesh wrote:
>>>
>>>> Hi,
>>>> What is the impact of changing PCB thickness?
>>>> To cut a long story short, the PCB fab house we use said they can't meet
>>>> our impedance requirement and achieve board thickness of 1.6mm.
>>>> They have to reduce the board thickness to 1.13mm to meet impedance
>>>> requirement.
>>>> He did say they could achieve both when we sent them the stack up pdf.
>>>>
>>> But
>>>
>>>> now they said they can't take decisions just based on stack up.
>>>>
>>>> Regards
>>>> -Hithesh
>>>>
>>>>
>>>>
>
>
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