Erik
Indeed, a sad day for the world environment, as were the days that two
countries reneged on their obligations that they had signed up for under
the Kyoto Protocol.
Brian
Erik de Kluizenaar wrote:
>
> My newspaper told me this morning that the final voting on RoHS and WEEE
> passed the European parliament yesterday.
> Does anyone have further details? ( Date that the law comes into place;
> how much time will the individual member states have to set up their
> system in accordance with the EU law; etceteras.)
> If yes, please share with the forum.
> Erik
> ---------------------------------------------------------------------------------------------------------------------------------------------
> Erik E. de Kluizenaar
> PHILIPS CFT - Electronic Packaging & Assembly (EP&A)
> Building SAQ-p, p/o box 218, 5600 MD Eindhoven - The Netherlands
> Tel/Fax: (+31 40 27) 36679/36815; E:mail [log in to unmask]
> PHILIPS homepage: http://www.philips.com; PHILIPS CFT homepage:
> http://www.cft.philips.com
> Internal PHILIPS only:
> http://pww.cft.philips.com/cfteurope/electronics/elpajo/index.htm
> ----------------------------------------------------------------------------------------------------------------------------------------------
>
>
>
>
>
>
>
>
> "Vladimir Igoshev" <[log in to unmask]>
>
> 2002-12-18 21:14
>
>
> To: E.E. de Kluizenaar/EHV/CFT/PHILIPS@EMEA3
> "(Leadfree Electronics Assembly Forum)" <[log in to unmask]>
> cc:
> Subject: RE: [LF] Leadfree Digest - 12 Dec 2002 to 13 Dec
> 2002 (#2002-157)
>
> Classification:
>
>
>
>
> Eric,
>
> In such a case, does the presence of only Ni3P in that darker strip we
> usually see on top of EN at the interface mean that all excess Ni in the
> strip has been consumed to form the Ni/Sn intermetallics? And if it
> does, then we should see "darkening" of the strip over time due to Ni
> diffusion from the underlaying region and in addition, a "plateau in the
> rate of the Ni/Sn intermetallics growth due to "lack" of Ni?
>
> Best regards,
>
> Vladimir
>
>
> Vladimir Igoshev, Ph. D.
> 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] <mailto:[log in to unmask]>
> -----Original Message-----
> From: [log in to unmask] [mailto:[log in to unmask]]
> Sent: Wednesday, December 18, 2002 6:20 AM
> To: (Leadfree Electronics Assembly Forum); Vladimir Igoshev
> Subject: Re: [LF] Leadfree Digest - 12 Dec 2002 to 13 Dec 2002 (#2002-157)
>
>
> Vladimir, all,
>
> You wrote "phosphorus enriched layer" instead of the compound Ni3P.
> I have positive evidence from my very experienced Philips-CFT Singapore
> collegue Dr. Radakrishnan, from in depth TEM analysis, that this phase
> really is the crystalline nickel-phosphide and not some undefined mixture.
>
> At the moment I do not see a way to "defeat nature" on this point.
> However, who knows which brilliant person will come up with a beautiful
> invention.
>
> Best regards,
> Erik
> ---------------------------------------------------------------------------------------------------------------------------------------------
> Erik E. de Kluizenaar
> PHILIPS CFT - Electronic Packaging & Assembly (EP&A)
> Building SAQ-p, p/o box 218, 5600 MD Eindhoven - The Netherlands
> Tel/Fax: (+31 40 27) 36679/36815; E:mail [log in to unmask]
> PHILIPS homepage: http://www.philips.com; PHILIPS CFT homepage:
> http://www.cft.philips.com
> Internal PHILIPS only:
> http://pww.cft.philips.com/cfteurope/electronics/elpajo/index.htm
> ----------------------------------------------------------------------------------------------------------------------------------------------
>
>
>
>
>
>
>
> Vladimir Igoshev <[log in to unmask]>
>
> Sent by:
> Leadfree <[log in to unmask]>
>
> 2002-12-17 19:17
> Please respond to "(Leadfree Electronics Assembly Forum)"; Please
> respond to Vladimir Igoshev
>
>
> To: [log in to unmask]
> cc: (bcc: E.E. de Kluizenaar/EHV/CFT/PHILIPS)
> Subject: Re: [LF] Leadfree Digest - 12 Dec 2002 to 13 Dec
> 2002 (#2002-157)
>
> Classification:
>
>
>
>
> Erik, your summary is great and I also want to thank everyone for the
> discussion.
> It looks like there is no way we can "fundamentally improve" the
> Ni3Sn4/phosphorus enriched layer interface (I put "phosphorus enriched
> layer" instead of the original Ni3P in the Erik's summary, because it
> seems like it should to be a mix of the Ni3P and nickel), or am I wrong
> and there is a way to "defeat" nature ?
>
> Best regards,
>
> Vladimir
>
> Vladimir Igoshev, Ph. D.
> 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] <mailto:[log in to unmask]>
>
>
> -----Original Message-----
> From: Automatic digest processor [mailto:[log in to unmask]]
> Sent: Saturday, December 14, 2002 1:00 AM
> To: Recipients of Leadfree digests
> Subject: Leadfree Digest - 12 Dec 2002 to 13 Dec 2002 (#2002-157)
>
>
> There is one message totalling 722 lines in this issue.
>
> Topics of the day:
>
> 1. "Brittle Fracture"
>
> -------------------------------------------------------------------------------Leadfee
> Mail List provided as a free service by IPC using LISTSERV 1.8d
> To unsubscribe, send a message to [log in to unmask] with following text in
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> Leadfree NOMAIL
> Search previous postings at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
> information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> ext.5315
> -------------------------------------------------------------------------------
>
> ----------------------------------------------------------------------
>
> Date: Fri, 13 Dec 2002 09:33:54 +0100
> From: Erik de Kluizenaar <[log in to unmask]>
> Subject: Re: "Brittle Fracture"
>
> This is a multipart message in MIME format.
> --=_alternative 002F346CC1256C8E_=
> Content-Type: text/plain; charset="us-ascii"
>
> Thanks for the addition Brian.
>
> That's the hypothesis that I always use here in Philips to explain to my
> collegues why nickel-gold solderability degrades to a reproducible extent
> in reflow soldering, with hardly any influence of reflow peak temperature
> and reflow time (five-fold reflow is still OK). Once that this fraction of
> the surface area (the bottoms of the pores) have been oxidized, the oxide
> patches may grow in thickness to a small extent, but the surface fraction
> remains the same. This extent of the decrease in solderability is such
> that a second or third soldering operation (double-sided reflow or wave
> after reflow) is no major problem, be it that contact time in wave
> soldering may have to be increased slightly.
>
> NB:
> Be aware of the fact that the gold of this plating has a huge
> environmental impact, orders of magnitude larger than that of lead.
> (Compare wire bonded ICs in which the gold bond wires with a thickness of,
> say, 25 mu almost completely determine the environmental impact.) So, it
> may be lead-free but it does not serve the initial goal of lowering
> environmental impact at all. If you want to choose relatively
> environmentally friendly finishes, think of Cu-OSP, chemical tin,
> electrolytic matt tin, chemical silver and refrain from the noble metals
> gold palladium and platinum.
>
> Best regards,
> Erik
> ---------------------------------------------------------------------------------------------------------------------------------------------
> Erik E. de Kluizenaar
> PHILIPS CFT - Electronic Packaging & Assembly (EP&A)
> Building SAQ-p, p/o box 218, 5600 MD Eindhoven - The Netherlands
> Tel/Fax: (+31 40 27) 36679/36815; E:mail [log in to unmask]
> PHILIPS homepage: http://www.philips.com; PHILIPS CFT homepage:
> http://www.cft.philips.com
> Internal PHILIPS only:
> http://pww.cft.philips.com/cfteurope/electronics/elpajo/index.htm
> ----------------------------------------------------------------------------------------------------------------------------------------------
>
>
>
>
>
>
>
>
>
>
> Brian Ellis <[log in to unmask]>
> 2002-12-12 17:58
>
>
> To: "(Leadfree Electronics Assembly Forum)" <[log in to unmask]>
> E.E. de Kluizenaar/EHV/CFT/PHILIPS@EMEA3
> cc:
> Subject: Re: [LF] "Brittle Fracture"
> Classification:
>
>
>
> Erik
>
> Good explanation. I'd like to add one more thing, if you will allow me:
> nickel very rapidly forms a thin, refractive, oxide layer if exposed to
> air. This is what maintains that brilliance with a slightly brownish
> cast on nickel-plated parts. This is normally unsolderable, except with
> halide-activated fluxes. As you have rightly pointed out, the gold is
> porous and there is a little area of nickel oxide at the foot of every
> pore. This myriad relatively unsolderable points also causes dewetting.
>
> Brian
>
> Erik de Kluizenaar wrote:
> >
> > Dear all,
> >
> > Let me try to explain some metallurgy behind the nickel-gold board
> > finish (also called ENIG; terrible acronym for a chemist/metallurgist
> > like myself) and the failure modes that can occur.
> >
> > 1. The electroless nickel plating has a built-in phosphorus content of
> > about 8 mass-%. This is inherent to the replinishing type of deposition
> > process and can not be avoided.
> > 2. The gold flash is produced by a chemical exchange process. Nickel
> > dissolves and the more noble gold ions are deposited. The thickness of
> > these gold layers is typicallly 0.05 - 0.2 micrometers. This implies
> > that these must be micro-porous. Otherwise, the reaction would stop at a
>
> > layer thickness in the order of 2 to 3 nanometers.
> > 3. The copper lands on which the finish is going to be applied, is
> > activated with zinc, extremely finely deispersed, to provide proper
> > adhesion and a fine-grained nickel microstructure.
> >
> > To arrive at a good quality finish, all the process steps mentioned
> > above, should be well optimized and controlled. (Following the
> > suppliers' process prescriptions is crucial for such processes.) If
> > something goes wrong, the following imperfections may occur:
> > - coarse nickel structure with irregular phosphorus distribution
> > - wrong phosphorus concentration (typically more than 8 %)
> > - passivation between nickel and gold (mainly determined by the rinsing
> > steps)
> > - poor gold deposit (too thin; too porous; uneven)
> >
> > Soldering with tin-based alloys, both lead-containing and lead-free,
> > will produce a ralatively complex intermetallic interface, from nickel
> > to solder:
> > - nickel phosphide, Ni3P (thickness sub-micron and very regular)
> > - nickel-tin, Ni3Sn4 (thickness typically 1-3 micrometers and very
> > irregular).
> > This intermetallic double layer has an intrinsic weakness against
> > bending and mechanical shock loading. This is particularly pronounced
> > with large and stiff components such as large BGAs. The fracture surface
>
> > lies in the interface between these two layers and looks as an adhesive
> > fracture. No brittle or ductile fracture details on either side of the
> > fracture to be found using SEM. (More detail should be investigated
> > using TEM and replica technology.) Microprobe analysis and
> > microsectioning have further proven that this fracture mode is as
> > described above.
> > The colour on the nickel side is dark grey. So, this can be called
> > "black pad".
> > All this does not mean that such joints are bad, but any chain has a
> > weakest link and with soldered joints on this type nickel-gold finish,
> > this intermetallic interface is the one, particularly with incidental
> > overloading such as mechanical shock.
> >
> > Now if the nickel quality is poor, this interface turns out to be really
>
> > weaker in many cases. Then, the strength may be insufficient. In those
> > cases, often but not always, the phosphorus content exceeds 8%. But we
> > also found good quality finishes with 9% so, phosphorus is not the
> > unique reliability indicator. However, processes are running out of
> > control with too high P-content so, it always requires action to be
> taken.
> >
> > The gold is micro-porous, see above. This implies that the nickel can be
>
> > attacked through the pores if improper rinsing procedures are applied.
> > This will result in the formation of corrosion products in the form of a
>
> > passivation layer, that cannot be removed by soldering fluxes. If a
> > passivation layer is present between nickel and gold, the gold will
> > readily dissolve and the solder will see an unsolderable surface. On
> > large solder lands this will be seen as severe dewetting and black pad,
> > and on small lands the solder will be covering the lands without really
> > adhering to those. So, fracture will occur at very low forces and the
> > pads will also be greyish-black. This type of "black pad" is the
> > dangerous one.
> >
> > Best regards,
> > Erik
> >
> ---------------------------------------------------------------------------------------------------------------------------------------------
> > Erik E. de Kluizenaar
> > PHILIPS CFT - Electronic Packaging & Assembly (EP&A)
> > Building SAQ-p, p/o box 218, 5600 MD Eindhoven - The Netherlands
> > Tel/Fax: (+31 40 27) 36679/36815; E:mail
> [log in to unmask]
> > PHILIPS homepage: http://www.philips.com; PHILIPS CFT homepage:
> > http://www.cft.philips.com
> > Internal PHILIPS only:
> > http://pww.cft.philips.com/cfteurope/electronics/elpajo/index.htm
> >
> ----------------------------------------------------------------------------------------------------------------------------------------------
>
> >
> >
> >
> >
> >
> >
> >
> >
> > Dave Hillman <[log in to unmask]>
> >
> > Sent by:
> > Leadfree <[log in to unmask]>
> >
> > 2002-12-11 00:09
> > Please respond to "(Leadfree Electronics Assembly Forum)"; Please
> > respond to ddhillma
> >
> >
> > To: [log in to unmask]
> > cc: (bcc: E.E. de Kluizenaar/EHV/CFT/PHILIPS)
> > Subject: Re: [LF] "Brittle Fracture"
> >
> > Classification:
> >
> >
> >
> >
> > Hi Bev! I have been using the following "definitions" of the two
> phenomena;
> > a) Black pad: a defect of immersion gold/electroless nickel (ENIG) pwb
> > surface finish associated with process control issues with the ENIG
> plating
> > chemistry/deposition process; b) Brittle Pad: a defect of ENIG pwb
> surface
> > finish associated with metallurgical phase formation and elemental
> > diffusion issues. This is how I have been keeping things straight
> between
> > Diet Coke's.
> >
> > Dave
> >
> > PS - I know you and Vladimir work in the same group -that's why I added
> the
> > "this is going to sound silly"... :)
> >
> >
> >
> >
> >
> >
> > Bev Christian <[log in to unmask]>@ipc.org> on 12/10/2002 07:23:13 AM
> >
> > Please respond to "(Leadfree Electronics Assembly Forum)"
> > <[log in to unmask]>; Please respond to Bev Christian
> > <[log in to unmask]>
> >
> > Sent by: Leadfree <[log in to unmask]>
> >
> >
> > To: [log in to unmask]
> > cc:
> >
> > Subject: Re: [LF] "Brittle Fracture"
> >
> >
> > Dave and Dave,
> > We (Vladimir and myself) are being told that Black Pad and Brittle Pad
> are
> > DIFFERENT phenomena. Any enlightenment would be appreciated.
> >
> > regards,
> > Bev Christian
> > Research in Motion
> >
> > PS Vladimir works for me and we sit in the same double cubicle!
> > -----Original Message-----
> > From: Dave Hillman [mailto:[log in to unmask]]
> > Sent: December 9, 2002 5:27 PM
> > To: [log in to unmask]
> > Subject: Re: [LF] "Brittle Fracture"
> >
> >
> > Hi Vladimir! This is going to sound silly but I recommend you check with
> > Bev Christian at RIM (his office should be close to yours!) - Bev should
> > have the last couple of IPC Conference Proceedings which contain a
> number
> > of good papers on the "black pad phenomena".
> >
> > Dave Hillman
> > Rockwell Collins
> > [log in to unmask]
> >
> >
> >
> >
> > Vladimir Igoshev <[log in to unmask]>@ipc.org> on 12/09/2002 03:27:19 PM
> >
> > Please respond to "(Leadfree Electronics Assembly Forum)"
> > <[log in to unmask]>; Please respond to Vladimir Igoshev
> > <[log in to unmask]>
> >
> > Sent by: Leadfree <[log in to unmask]>
> >
> >
> > To: [log in to unmask]
> > cc:
> >
> > Subject: [LF] "Brittle Fracture"
> >
> >
> > Dear All,
> >
> > I'm looking for any references related to so called "Brittle Fracture"
> > phenomenon, which sometime can be obeserved in solder joints between BGA
> > componets and ENIG finished boards.
> >
> > Vladimir Igoshev, Ph.D.
> > Research in Motion
> > Canada
> >
> >
> -------------------------------------------------------------------------------Leadfee
> >
> >
> > Mail List provided as a free service by IPC using LISTSERV 1.8d
> > To unsubscribe, send a message to [log in to unmask] with following text
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> > the BODY (NOT the subject field): SIGNOFF Leadfree
> > To temporarily stop delivery of Leadree for vacation breaks send: SET
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> > Search previous postings at: http://listserv.ipc.org/archives
> > Please visit IPC web site http://www.ipc.org/html/forum.htm for
> additional
> > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> > ext.5315
> >
> -------------------------------------------------------------------------------
> >
> >
> >
> -------------------------------------------------------------------------------Leadfee
> >
> > Mail List provided as a free service by IPC using LISTSERV 1.8d
> > To unsubscribe, send a message to [log in to unmask] with following text
> in
> > the BODY (NOT the subject field): SIGNOFF Leadfree
> > To temporarily stop delivery of Leadree for vacation breaks send: SET
> > Leadfree NOMAIL
> > Search previous postings at: http://listserv.ipc.org/archives
> > Please visit IPC web site http://www.ipc.org/html/forum.htm for
> additional
> > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> > ext.5315
> >
> -------------------------------------------------------------------------------
> >
> >
> >
> -------------------------------------------------------------------------------Leadfee
> >
> > Mail List provided as a free service by IPC using LISTSERV 1.8d
> > To unsubscribe, send a message to [log in to unmask] with following text
> in
> > the BODY (NOT the subject field): SIGNOFF Leadfree
> > To temporarily stop delivery of Leadree for vacation breaks send: SET
> > Leadfree NOMAIL
> > Search previous postings at: http://listserv.ipc.org/archives
> > Please visit IPC web site http://www.ipc.org/html/forum.htm for
> additional
> > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> > ext.5315
> >
> -------------------------------------------------------------------------------
> >
> >
> -------------------------------------------------------------------------------Leadfee
>
> > Mail List provided as a free service by IPC using LISTSERV 1.8d
> > To unsubscribe, send a message to [log in to unmask] with following text
> in
> > the BODY (NOT the subject field): SIGNOFF Leadfree
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> > Leadfree NOMAIL
> > Search previous postings at: http://listserv.ipc.org/archives
> > Please visit IPC web site http://www.ipc.org/html/forum.htm for
> additional
> > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
>
> > ext.5315
> >
> -------------------------------------------------------------------------------
> >
> >
> -------------------------------------------------------------------------------Leadfee
>
> > Mail List provided as a free service by IPC using LISTSERV 1.8d To
> > unsubscribe, send a message to [log in to unmask] with following text in
> > the BODY (NOT the subject field): SIGNOFF Leadfree To temporarily stop
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>
> > previous postings at: http://listserv.ipc.org/archives Please visit IPC
> > web site http://www.ipc.org/html/forum.htm for additional information,
> > or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
> >
> -------------------------------------------------------------------------------
>
> >
>
>
>
>
>
> -------------------------------------------------------------------------------Leadfee
> Mail List provided as a free service by IPC using LISTSERV 1.8d
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Leadfree
> To temporarily stop delivery of Leadree for vacation breaks send: SET
> Leadfree NOMAIL
> Search previous postings at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
> information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> ext.5315
> -------------------------------------------------------------------------------
>
> --=_alternative 002F346CC1256C8E_=
> Content-Type: text/html; charset="us-ascii"
>
>
> <br><font size=2 face="sans-serif">Thanks for the addition Brian.</font>
> <br>
> <br><font size=2 face="sans-serif">That's the hypothesis that I always
> use here in Philips to explain to my collegues why nickel-gold
> solderability degrades to a reproducible extent in reflow soldering,
> with hardly any influence of reflow peak temperature and reflow time
> (five-fold reflow is still OK). Once that this fraction of the surface
> area (the bottoms of the pores) have been oxidized, the oxide patches
> may grow in thickness to a small extent, but the surface fraction
> remains the same. This extent of the decrease in solderability is such
> that a second or third soldering operation (double-sided reflow or wave
> after reflow) is no major problem, be it that contact time in wave
> soldering may have to be increased slightly.</font>
> <br>
> <br><font size=2 face="sans-serif">NB:</font>
> <br><font size=2 face="sans-serif">Be aware of the fact that the gold of
> this plating has a huge environmental impact, orders of magnitude larger
> than that of lead. (Compare wire bonded ICs in which the gold bond wires
> with a thickness of, say, 25 mu almost completely determine the
> environmental impact.) So, it may be lead-free but it does not serve the
> initial goal of lowering environmental impact at all. If you want to
> choose relatively environmentally friendly finishes, think of Cu-OSP,
> chemical tin, electrolytic matt tin, chemical silver and refrain from
> the noble metals gold palladium and platinum.</font>
> <br>
> <br><font size=2 face="sans-serif">Best regards,</font>
> <br><font size=2 face="sans-serif">Erik<br>
> ---------------------------------------------------------------------------------------------------------------------------------------------<br>
> Erik E. de Kluizenaar<br>
> PHILIPS CFT - Electronic Packaging & Assembly (EP&A)<br>
> Building SAQ-p, p/o box 218, 5600 MD Eindhoven - The
> Netherlands<br>
> Tel/Fax: (+31 40 27) 36679/36815; E:mail
> [log in to unmask]<br>
> PHILIPS homepage: http://www.philips.com; PHILIPS CFT homepage:
> http://www.cft.philips.com<br>
> Internal PHILIPS only:
> http://pww.cft.philips.com/cfteurope/electronics/elpajo/index.htm<br>
> ----------------------------------------------------------------------------------------------------------------------------------------------</font>
> <br>
> <br>
> <br>
> <table width=100%>
> <tr valign=top>
> <td>
> <td>
> <br>
> <br>
> <br>
> <br>
> <br><font size=1 face="sans-serif"><b>Brian Ellis
> <[log in to unmask]></b></font>
> <p><font size=1 face="sans-serif">2002-12-12 17:58</font>
> <br>
> <td><font size=1 face="Arial"> </font>
> <br><font size=1 face="sans-serif"> To:
> "(Leadfree Electronics Assembly
> Forum)" <[log in to unmask]><br>
> E.E. de Kluizenaar/EHV/CFT/PHILIPS@EMEA3</font>
> <br><font size=1 face="sans-serif"> cc:
> </font>
> <br><font size=1 face="sans-serif"> Subject:
> Re: [LF] "Brittle Fracture"</font>
> <p><font size=1 face="sans-serif">
> Classification: </font>
> <br></table>
> <br>
> <br>
> <br><font size=2 face="Courier New">Erik<br>
> <br>
> Good explanation. I'd like to add one more thing, if you will allow me: <br>
> nickel very rapidly forms a thin, refractive, oxide layer if exposed to <br>
> air. This is what maintains that brilliance with a slightly brownish <br>
> cast on nickel-plated parts. This is normally unsolderable, except with <br>
> halide-activated fluxes. As you have rightly pointed out, the gold is <br>
> porous and there is a little area of nickel oxide at the foot of every <br>
> pore. This myriad relatively unsolderable points also causes dewetting.<br>
> <br>
> Brian<br>
> <br>
> Erik de Kluizenaar wrote:<br>
> > <br>
> > Dear all,<br>
> > <br>
> > Let me try to explain some metallurgy behind the nickel-gold board <br>
> > finish (also called ENIG; terrible acronym for a
> chemist/metallurgist <br>
> > like myself) and the failure modes that can occur.<br>
> > <br>
> > 1. The electroless nickel plating has a built-in phosphorus content
> of <br>
> > about 8 mass-%. This is inherent to the replinishing type of
> deposition <br>
> > process and can not be avoided.<br>
> > 2. The gold flash is produced by a chemical exchange process.
> Nickel <br>
> > dissolves and the more noble gold ions are deposited. The thickness
> of <br>
> > these gold layers is typicallly 0.05 - 0.2 micrometers. This
> implies <br>
> > that these must be micro-porous. Otherwise, the reaction would stop
> at a <br>
> > layer thickness in the order of 2 to 3 nanometers.<br>
> > 3. The copper lands on which the finish is going to be applied, is <br>
> > activated with zinc, extremely finely deispersed, to provide proper
> <br>
> > adhesion and a fine-grained nickel microstructure.<br>
> > <br>
> > To arrive at a good quality finish, all the process steps mentioned
> <br>
> > above, should be well optimized and controlled. (Following the <br>
> > suppliers' process prescriptions is crucial for such processes.) If
> <br>
> > something goes wrong, the following imperfections may occur:<br>
> > - coarse nickel structure with irregular phosphorus distribution<br>
> > - wrong phosphorus concentration (typically more than 8 %)<br>
> > - passivation between nickel and gold (mainly determined by the
> rinsing <br>
> > steps)<br>
> > - poor gold deposit (too thin; too porous; uneven)<br>
> > <br>
> > Soldering with tin-based alloys, both lead-containing and
> lead-free, <br>
> > will produce a ralatively complex intermetallic interface, from
> nickel <br>
> > to solder:<br>
> > - nickel phosphide, Ni3P (thickness sub-micron and very regular)<br>
> > - nickel-tin, Ni3Sn4 (thickness typically 1-3 micrometers and very <br>
> > irregular).<br>
> > This intermetallic double layer has an intrinsic weakness against <br>
> > bending and mechanical shock loading. This is particularly
> pronounced <br>
> > with large and stiff components such as large BGAs. The fracture
> surface <br>
> > lies in the interface between these two layers and looks as an
> adhesive <br>
> > fracture. No brittle or ductile fracture details on either side of
> the <br>
> > fracture to be found using SEM. (More detail should be investigated
> <br>
> > using TEM and replica technology.) Microprobe analysis and <br>
> > microsectioning have further proven that this fracture mode is as <br>
> > described above.<br>
> > The colour on the nickel side is dark grey. So, this can be called <br>
> > "black pad".<br>
> > All this does not mean that such joints are bad, but any chain has
> a <br>
> > weakest link and with soldered joints on this type nickel-gold
> finish, <br>
> > this intermetallic interface is the one, particularly with
> incidental <br>
> > overloading such as mechanical shock.<br>
> > <br>
> > Now if the nickel quality is poor, this interface turns out to be
> really <br>
> > weaker in many cases. Then, the strength may be insufficient. In
> those <br>
> > cases, often but not always, the phosphorus content exceeds 8%. But
> we <br>
> > also found good quality finishes with 9% so, phosphorus is not the <br>
> > unique reliability indicator. However, processes are running out of
> <br>
> > control with too high P-content so, it always requires action to be
> taken.<br>
> > <br>
> > The gold is micro-porous, see above. This implies that the nickel
> can be <br>
> > attacked through the pores if improper rinsing procedures are
> applied. <br>
> > This will result in the formation of corrosion products in the form
> of a <br>
> > passivation layer, that cannot be removed by soldering fluxes. If a
> <br>
> > passivation layer is present between nickel and gold, the gold will
> <br>
> > readily dissolve and the solder will see an unsolderable surface.
> On <br>
> > large solder lands this will be seen as severe dewetting and black
> pad, <br>
> > and on small lands the solder will be covering the lands without
> really <br>
> > adhering to those. So, fracture will occur at very low forces and
> the <br>
> > pads will also be greyish-black. This type of "black pad"
> is the <br>
> > dangerous one.<br>
> > <br>
> > Best regards,<br>
> > Erik<br>
> >
> ---------------------------------------------------------------------------------------------------------------------------------------------<br>
> > Erik E. de Kluizenaar<br>
> > PHILIPS CFT - Electronic Packaging & Assembly (EP&A)<br>
> > Building SAQ-p, p/o box 218, 5600 MD Eindhoven - The
> Netherlands<br>
> > Tel/Fax: (+31 40 27) 36679/36815; E:mail
> [log in to unmask]<br>
> > PHILIPS homepage: http://www.philips.com; PHILIPS CFT
> homepage: <br>
> > http://www.cft.philips.com<br>
> > Internal PHILIPS only: <br>
> >
> http://pww.cft.philips.com/cfteurope/electronics/elpajo/index.htm</font>
> <br><font size=2 face="Courier New">>
> ----------------------------------------------------------------------------------------------------------------------------------------------
> <br>
> > <br>
> > <br>
> > <br>
> > <br>
> > <br>
> > <br>
> > <br>
> > <br>
> > Dave Hillman <[log in to unmask]><br>
> > <br>
> > Sent by:<br>
> > Leadfree <[log in to unmask]><br>
> > <br>
> > 2002-12-11 00:09<br>
> > Please respond to "(Leadfree Electronics Assembly
> Forum)"; Please <br>
> > respond to ddhillma<br>
> > <br>
> > <br>
> > To:
> [log in to unmask]<br>
> > cc: (bcc:
> E.E. de Kluizenaar/EHV/CFT/PHILIPS)<br>
> > Subject: Re:
> [LF] "Brittle Fracture"<br>
> > <br>
> > Classification:
> <br>
> > <br>
> > <br>
> > <br>
> > <br>
> > Hi Bev! I have been using the following "definitions" of
> the two phenomena;<br>
> > a) Black pad: a defect of immersion gold/electroless nickel (ENIG)
> pwb<br>
> > surface finish associated with process control issues with the ENIG
> plating<br>
> > chemistry/deposition process; b) Brittle Pad: a defect of ENIG pwb
> surface<br>
> > finish associated with metallurgical phase formation and elemental<br>
> > diffusion issues. This is how I have been keeping things straight
> between<br>
> > Diet Coke's.<br>
> > <br>
> > Dave<br>
> > <br>
> > PS - I know you and Vladimir work in the same group -that's why I
> added the<br>
> > "this is going to sound silly"... :)<br>
> > <br>
> > <br>
> > <br>
> > <br>
> > <br>
> > <br>
> > Bev Christian <[log in to unmask]>@ipc.org> on 12/10/2002
> 07:23:13 AM<br>
> > <br>
> > Please respond to "(Leadfree Electronics Assembly Forum)"<br>
> > <[log in to unmask]>; Please respond to
> Bev Christian<br>
> > <[log in to unmask]><br>
> > <br>
> > Sent by: Leadfree <[log in to unmask]><br>
> > <br>
> > <br>
> > To: [log in to unmask]<br>
> > cc:<br>
> > <br>
> > Subject: Re: [LF] "Brittle Fracture"<br>
> > <br>
> > <br>
> > Dave and Dave,<br>
> > We (Vladimir and myself) are being told that Black Pad and Brittle
> Pad are<br>
> > DIFFERENT phenomena. Any enlightenment would be appreciated.<br>
> > <br>
> > regards,<br>
> > Bev Christian<br>
> > Research in Motion<br>
> > <br>
> > PS Vladimir works for me and we sit in the same double cubicle!<br>
> > -----Original Message-----<br>
> > From: Dave Hillman [mailto:[log in to unmask]]<br>
> > Sent: December 9, 2002 5:27 PM<br>
> > To: [log in to unmask]<br>
> > Subject: Re: [LF] "Brittle Fracture"<br>
> > <br>
> > <br>
> > Hi Vladimir! This is going to sound silly but I recommend you check
> with<br>
> > Bev Christian at RIM (his office should be close to yours!) - Bev
> should<br>
> > have the last couple of IPC Conference Proceedings which contain a
> number<br>
> > of good papers on the "black pad phenomena".<br>
> > <br>
> > Dave Hillman<br>
> > Rockwell Collins<br>
> > [log in to unmask]<br>
> > <br>
> > <br>
> > <br>
> > <br>
> > Vladimir Igoshev <[log in to unmask]>@ipc.org> on 12/09/2002
> 03:27:19 PM<br>
> > <br>
> > Please respond to "(Leadfree Electronics Assembly Forum)"<br>
> > <[log in to unmask]>; Please respond to
> Vladimir Igoshev<br>
> > <[log in to unmask]><br>
> > <br>
> > Sent by: Leadfree <[log in to unmask]><br>
> > <br>
> > <br>
> > To: [log in to unmask]<br>
> > cc:<br>
> > <br>
> > Subject: [LF] "Brittle Fracture"<br>
> > <br>
> > <br>
> > Dear All,<br>
> > <br>
> > I'm looking for any references related to so called "Brittle
> Fracture"<br>
> > phenomenon, which sometime can be obeserved in solder joints
> between BGA<br>
> > componets and ENIG finished boards.<br>
> > <br>
> > Vladimir Igoshev, Ph.D.<br>
> > Research in Motion<br>
> > Canada<br>
> > <br>
> >
> -------------------------------------------------------------------------------Leadfee<br>
> > <br>
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> additional<br>
> > information, or contact Keach Sasamori at [log in to unmask] or
> 847-509-9700<br>
> > ext.5315<br>
> >
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> ------------------------------
>
> End of Leadfree Digest - 12 Dec 2002 to 13 Dec 2002 (#2002-157)
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