Jumping onboard train at full speed, I don't know if I came on right waggon, but Nickel question interests me at the moment. We solder tiny glass feedtrues in a large aluminium package. Use ordinary SnPb circular preforms with some percentage Ag. And Kester flux 185. Flux preheat in +100 Centigrade oven for 10 minutes and then VP soldering for about 2 minutes at +205 Centigrades. The package has bright electrolytic nickel, 20 micrometers thick (the plater is generous!. As all know, nickel has poor to medium wettability and, consequently, we play russian roulette some days, never know what package will cause trouble.
Q1: Anyone with experience of activating the solder site (the nickel) with acidous solution before fluxing?
Q2: Anyone who knows better flux than Kester 185?
Thanks
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Frank Kimmey
Sent: den 24 augusti 2004 21:08
To: [log in to unmask]
Subject: Re: [TN] Low Stress Plating Question
Carrie,
IPC-2252 (RF/Microwave Design Guide) calls out 50 to 200uin for electrodeposit and 200uin to 300uin for electroless nickel and IPC-4552 (ENIG Plating) calls out 120uin to 240uin for nickel.
These numbers are from my proposal copies and may have changed slightly with release (though I don't expect they did).
As an example, I use 50 to 150 microinches of Electroless Nickel beneath 3 to 8 microinches of Immersion Gold in my ENIG documentation.
As to your original questions:
1. Nickel is used as the solderable surface and as a barrier to keep copper from leaching away the gold final finish. Due to oxidation it is necessary to protect the nickel from environmentals (nickel oxide does not solder well) and is there fore coated with a thin layer of gold.
2. 500 microinches is way to much (my opinion) due to the inability of that thick of a material to stretch with Z-axis thermal expansions (this could cause reliability issues from barrel cracking during thermal stress). I think you will most likely find Board Houses are comfortable with a minimum 50 microinch requirement.
Hope it helps,
FNK
Frank N Kimmey CID+
Principle PCB Designer
Powerwave Tecnologies Inc
Office 916-941-3159
Fax 916-941-3195
Cellular 916-804-2491
-----Original Message-----
From: R Sedlak [mailto:[log in to unmask]]
Sent: Tuesday, August 24, 2004 7:36 AM
To: [log in to unmask]
Subject: Re: [TN] Low Stress Plating Question
Carrie:
Not sure I qualify as a plating "expert"...
But, it would appear that somebody got a decimal point in the wrong place, as 50 microinches is more typical for Nickel thickness...
Are you talking about Electroless Nickel, or electroplated?
Rudy Sedlak
RD Chemical Company
"Morse, Carrie" <[log in to unmask]> wrote:
For all you Plating Experts
We have a customer specifying 500 micro inches minimum of Low Stress
Nickel under 3-5 micro inches of Gold.
1. What is the purpose of the Ni? Is it to aid in bonding the gold?
2. Is 500 micro inches too much? What are board houses capable of
doing without damaging the board and....what would board houses like to
see for a minimum specification on a note?
Thanks,
Carrie
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