Victor,
The notes from John covers a lot, be clear that the Gold thickness
in John's spec are for the gold fingers as he indicated. IPC 4552 is the new
guidance document for gold processing. For a solderable finish I would
recommend an Electroless Nickel thickness of 200 micro inches typical and a
Gold thickness of 3-5 micro inches, 99.9% pure, soft gold.
That being said and although vendors seem to indicate they have a handle on
the black pad issues, I have recommended against it's use on our products.
More processing steps more things to go wrong on the manufacturing side.
More difficult to wet the Nickel on the assembly side. I have recommended
Immersion Silver as the PbF alternative.
Take a look at the IPC-4101 for laminate properties. The things to pay
attention to are, the Tg, Td and CTE change for T greater than Tg and T260
delamination.
Remember it's not only the choice of finish which will affect reliability
and process compatibility but the choice of dielectric material.
Careful with the marking as well. RoHS compliance on the board surface does
not necessarily mean the assembly is RoHS compliant.
Hope it helps.
Regards,
LS
-----Original Message-----
From: Victor G. Hernandez [mailto:[log in to unmask]]
Sent: Tuesday, March 21, 2006 3:19 PM
To: [log in to unmask]
Subject: Re: PCB Mfg. Note for ENIG finish
Is there supporting studies that support ENIG PWB surface finish with LF
solder process.
Victor,
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Frank W
Sent: Tuesday, March 21, 2006 1:44 PM
To: [log in to unmask]
Subject: Re: [LF] PCB Mfg. Note for ENIG finish
Here's what we propose to use
1. ALL MATERIALS ARE TO BE ROHS COMPLIANT.
FABRICATE PER ANSI/IPC-A-600,IPC-QE-605,
IPC-4101,IPC-4552 AND IPC-SM-840 SPECIFICATIONS.
2. MATERIAL: .056 THK (.062 MAX) ROHS COMPLIANT
FR-4 PER IPC-4101 WITH MINIMUM Tg 170 DEGREES C OR HIGHER,
Td 340 DEGREES C OR HIGHER AND FLAME RATED UL 94V-0.
3. STACK-UP TO BE SYMMETRICAL ABOUT CORE.
.005" TRACES ON LAYER 1 ARE 75 OHMS NOMINAL REFERENCES TO LAYER 2.
.010 WIDTH/.010 SPACE TRACES ON LAYER 1 ARE 100 OHMS (DIFFERENTIAL
PAIR)
NOMINAL REFERENCED TO LAYER 2. SEE LAYER STACK (FIGURE 1)
4. PLATING TO BE ROHS COMPLIANT PER IPC-4552.
ELECTROLESS NICKEL/IMMERSION GOLD.
5. UNLESS OTHERWISE SPECIFIED, ALL HOLES TO BE PLATED.
VIAS TO BE PLUGGED AND TENTED, SURFACE TO BE FLAT ON PRIMARY SIDE.
6. SOLDERMASK BOTH SIDES OF BOARD OVER BARE COPPER WITH ROHS
COMPLIANT MATERIAL PER ANSI/IPC-SM-840,
COLOUR SHALL BE GREEN.
7. APPLY SILKSCREEN TO BOTH SIDES OF BOARD USING NON-CONDUCTIVE
ROHS COMPLIANT WHITE EPOXY INK.
8. PCB MANUFACTURE LOGO, UL MARKING, DATE-CODE
AND ROHS COMPLIANT SYMBOL TO BE APPLIED ON SOLDER SIDE IN AREA SHOWN
9. CARD EDGE CONNECTOR TO BE ELECTROLYTIC HARD GOLD PLATED
OVER NICKEL (150-200 MICROINCH NICKEL/50 MICROINCH GOLD)
AND BEVELLED, SEE DETAIL "A"
10. PACKAGED PCBS TO HAVE NORPAK PART NUMBER LATEST REV
AND "ROHS COMPLIANT" PLACED ON EACH PACKAGE.
[log in to unmask] wrote:
> We are ordering our first beta runs of ENIG finish boards. What notes,
> if any, are people using to communicate specific info about the finish
> (such as in a README file to the PCB fab house)?
>
>
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