I didn't know that speaking in SI unit would cause so much troubles..:) Sorry, next time I will translate it to "US" language, well may be I will not it was pretty fun.....
In any case as Vladimir mention, the Intermetallic thickness depends on the metal, and also on the solder type (LF and SnPb) and the liquidus time.
You can look at the paper "Reflow Profiling: Time above Liquidus" at AIM site www.aimsolder.com as an example. There are many papers dealing with the Intermetallic layers created during the reflow many of them (actually most of them in these RoHS days) comparing it to LF soldering. As long as you are below 6 micron =6 micro Meter = 236.22 micro Inches you are, probably, in the safe side. After one reflow time you should see about 0.5-2 micron of intermetalic layers, and it will increase with each reflowing.
Regards,
Dr. Gil Zilber
Technologist, Elta system Ltd.
Tel. +972-8-8577240
Mobile +972-54-4983222
http://www.iai.co.il/site/en/iai.asp?pi=17887
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
Sent: Monday, November 28, 2005 5:00 PM
To: [log in to unmask]
Subject: Re: [TN] Intermetallic Layer
And since the problem has been solved, it's time to get back to the original question Antonio asked. :-)
There are a few things to keep in mind about intermetallics. First of all, at a given reflow profile its thickness will depend on the substrate (or lead frame in that case) material (finish). Alloy 42 will form an extremely thin layer (sometimes barely seen), while Cu - the thickest one (with Ni and it's "combinations" will be somewhere in between).
There are no written numbers for either case (substrate). People usually say: it has be not thin and not thick. I usually "happy" if see something around 1 - 2 micron (not microinches, which I normally wouldn't see :-)) for either one.
There are a few papers showing that if the thickness of a Cu/Sn intermetallics layer exceeds 5 - 7 microns, its fracture toughness drops (which isn't necessarily a very bad thing, but I would be alerted).
Regards,
Vladimir
Vladimir Igoshev, Ph. D.
Senior Materials Researcher
Research in Motion
451 Phillip St.
Waterloo, ON, N2L 3X2
Voice: (+1) 519-888-7465, ext. 5283
Fax: (+1) 519-886-0863
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Stadem, Richard
Sent: Monday, November 28, 2005 9:37 AM
To: [log in to unmask]
Subject: Re: [TN] Intermetallic Layer
We solve the world's biggest problems on Monday mornings.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON
Sent: Monday, November 28, 2005 8:32 AM
To: [log in to unmask]
Subject: Re: [TN] Intermetallic Layer
Victor,
A micrometer (micron) is a millionth of a meter.
A microinch is a millionth of an inch.
An inch is smaller than a meter.
Therefore a micrinch is smaller than a micrometer.
You may be getting confused with nanometers which are a millionth of a millimetre and are indeed, very small.
Regards,
Eric Christison
Mechanical Engineer
Home, Personal, Communication Sector - Imaging Division STMicroelectronics
33 Pinkhill
Edinburgh
EH12 7BF
Tel: +44 (0)131 336 6165
Fax: +44 (0)131 336 6001
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor G.
> Hernandez
> Sent: Monday, November 28, 2005 2:24 PM
> To: [log in to unmask]
> Subject: Re: [TN] Intermetallic Layer
>
>
> I have been stating all along that MICRONS are a SMALLER unit of
> measure than MICRO INCHES.
>
> Victor,
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Indrek Rebane
> Sent: Monday, November 28, 2005 7:56 AM
> To: [log in to unmask]
> Subject: Re: [TN] Intermetallic Layer
>
> Hi Victor,
>
> Victor G. Hernandez wrote:
> > Microns are smaller units of measure than MICRO INCHES.
>
> You seem to be confusing microinches with mils. One microinch is
> thousandth of mil, which is thousandth of inch. One microinch is
> 0.0254 microns.
>
> Indrek,
> Actually a proponent of the SI (Metric) system.
>
> --
> Indrek Rebane
> Borthwick-Pignon OÜ, R&D
> Riia 185, 51014 Tartu, Estonia
> Phone: +372 7 302 641, Fax: +372 7 383 041
>
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