Ian Squires wrote:
>
> Help,
> Looking at substrate thickness on PWB
> if i specify 2oz copper 1.6 mm would the substrate be the same size, thicker or thinner than 1oz copper 1.6 mm.
>
> Many thanks for any speedy replies (one of those urgent ones where the boss man is standing over me).
>
> Regards
> Ian Squires
> Senior Production Engineer
> -------------------------------------------------------
>
> Graseby Dynamics Ltd
> A Smiths Industries Company
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>
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HELLO IAN,

IF YOU ARE SPEAKING IN GENERAL TERMS ABOUT COMMONLY ORDERED
MATERIAL, THAN MY EXPERIENCE HAS BEEN THAT THE WAY PEOPLE REFER TO
MATERIAL DEPENDS ON IF IT IS A DOUBLE-SIDED BOARD OR CORE LAMINATE THAT
WILL BE USED TO BUILD A MULTILAYER.  (ALL EX. BELOW ARE IN INCHES).

IF IT DOUBLE-SIDED: STANDARD .062 1/1 MATERIAL WOULD HAVE A LAMINATE
THICKNESS OF .0592 WITH A .0014 COPPER THICKNESS ON THE TOP AND BOTTOM.
IF YOU SPEC .062 2/2, STANDARD LAMINATE THICKNESS IS .0564 WITH .0028
THICK COPPER ON TOP AND BOTTOM.  OVERALL THICKNESS REMAINS AT .062.

IF IT IS CORE MAT'L FOR MULTILAYER: LET'S SAY 2 .014 CORES ARE BEING
USED ON A 6 LYR WITH A FINISHED OVERALL THICKNESS OF .062 AFTER
LAMINATION.  IF YOU REFER TO .014 1/1 THAN THE LAMINATE THICKNESS IS
.014 WITH AN OVERALL THICKNESS OVER COPPER OF .0168.  IF YOU REFER TO
.014 2/2 THAN ONCE AGAIN LAMINATE THICKNESS IS .014 BUT OVERALL
THICKNESS IS NOW .0196.

OF COURSE WHEN YOU GO TO ORDER MATERIAL FROM A VENDOR, THEY DON'T
NECESSARILY KNOW IF YOU ARE BUILDING A M/L OR NOT.  THE GOOD NEWS IS
THAT THERE IS A VERY CLEAR CONCISE WAY OF CALLING OUT WHAT THICKNESS OF
LAMINATE YOU WANT AND WHAT COPPER WEIGHT YOU WOULD LIKE (AS WELL AS
THICKNESS TOLERANCES, PITS AND DENTS CLASSIFICATION AND WARP & TWIST
ALLOWANCES, IF CRITICAL) IN MIL SPEC 13949 (WHICH IPC IS CURRENTLY
CHANGING (HAS ALREADY CHANGED?).  PERHAPS SOMEONE THERE CAN BRING YOU UP
TO SPEED ON THE NEW SPEC IF IT HAS NOT ALREADY BEEN COVERED IN THIS
FORUM.

JOHN DENTON
OMNI PWB

I'M SURE THE IPC PEOPLE CAN GIVE YOU THE NEW SPEC NUMBER AND

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