Dave, Does anyone have any numbers on wet-ability? Is there such a measurement? This is a constant "You Know What Contest" between folks who want it flat and folks who want it cheap. I admit I am in the cheap camp but I still want it right. The bad stuff I hear about with ENIG is all related to Black Pad hype. It might be all nonsense as far as I know. Isn't there anyway to get good solid numbers on how surfaces wet? In the last few emails I finally got the bad info (other than flat) on HASL, I am delighted to get a serious problem with HASL understood. I have "Played" with ENIG boards and with HASL (SnPb) boards, I assume both had "Good" finishes. With flux and SnPb solders the HASL seemed to accept a reflow better than ENIG. The edges seem to spread out better. With paste covering the ENIG maybe that is a non-issue. I have seen black pad but never a bad HASL so I am biased. Does anyone have any wet-ability numbers? Thanks, Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Friday, November 06, 2009 8:59 PM To: [log in to unmask] Subject: Re: [TN] BGA Balls Hi Bob - If we only lived in the town of Perfect, then all finishes would work and none of them would have any disadvantages. All finishes - OSP, HASL, immersion silver, immersion tin, ENIG, ENEPIG, etc - have both disadvantages and advantages. The real key to getting good printed wiring board surface finishes isn't selecting the "right one" but working closely with your printed wiring board fabricators to get consistency/reproducibility in the surface finish you specify. You obviously have a great relationship with a pwb fabricator who understands their HASL process and produces a very good product. The same can be said for other pwb fabricators who focus on the other pwb finishes. As a general rule, more folks are getting better consistency with the immersion finishes than HASL - that isn't a knock on HASL as a surface finish but more of an indication of the availability of pwb fabricators who understand and produce quality HASL finishes. There are still a large number of avionics assemblers who use all of the pwb surface finishes for a variety of applications. There are not "bad" surface finishes - just surface finishes with different characteristics. Dave Robert Kondner <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 11/06/2009 05:47 PM Please respond to [log in to unmask] To [log in to unmask] cc Subject Re: [TN] BGA Balls Hi, Ok, that makes sense. So which is worse? ENIG with bad plating. HASL with bad coatings? Does it matter? Maybe the questions is how often does bad ENIG happen compared with bad HASL? While I have not seen bad HASL I do believe it happens. If both finishes are good is there any difference in how the two good surfaces wet? Thanks, Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Friday, November 06, 2009 6:36 PM To: [log in to unmask] Subject: Re: [TN] BGA Balls Hi Werner! I suspect you asked this question intentionally so I'll provide the answer you were expecting - the HASL process was incorrectly applied to the board resulting in the thin solder coating. A thin coating results in oxidized IMC which is nonwettable in many standard soldering processes. Dave Hillman Rockwell Collins [log in to unmask] Werner Engelmaier <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 11/06/2009 08:48 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Werner Engelmaier <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] BGA Balls Hi Ioan, What is causing this is that too much solder was blown off the surface leaving not enough solder on top if the IMCs. Werner -----Original Message----- From: Ioan Tempea <[log in to unmask]> To: [log in to unmask] Sent: Fri, Nov 6, 2009 9:28 am Subject: Re: [TN] BGA Balls Well, Bob, Until 5 months ago I had not seen issues with HASL either, but since then this finish is the biggest issue I have ever had, for a particular product. Basically we're talking about pads with uneven SnPb thickness, especially on fine pitch parts, where the protective layer is getting so thin towards the extremities of pads that I only end up with intermetallics, that I cannot solder on. What causes this? Still no exact idea, although I have intensively questioned Technet and our PCB fab. Best regards, Ioan Tempea, ing. Ingénieur Principal de Fabrication / Senior Manufacturing Engineer T | 450.967.7100 ext.244 E | [log in to unmask] W | www.digico.cc N'imprimer que si nécessaire - Print only if you must -----Message d'origine----- De : Robert Kondner [mailto:[log in to unmask]] Envoyé : Friday, November 06, 2009 9:02 AM À : [log in to unmask] Objet : Re: [TN] BGA Balls Rex, ENIG seems like a finish that lot of folks love, a big reason is it is flat. I must have tunnel vision because I read on this link the problems with bad ENIG. Flat is not an issue with solder paste applied, right? I am using HASL and it just works so well for me. Now HASL might not work for everyone but I just can not jam into my neurons why. Can anyone help here? Thanks, Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Rex Waygood Sent: Friday, November 06, 2009 5:14 AM To: [log in to unmask] Subject: Re: [TN] BGA Balls Ummm. A few things come to mind at the moment Humble Pie Egg on Face Less haste more speed Live and learn Etc Shortly after the post below I decided to look at the 'posted' pcb in more detail. I decided to try and pry off another BGA (It's a flash part I think) I just used my finger nail and there was a slight creaking noise and the part flicked off (without damaging my finger nail) Just for fun I did another. Photo to follow from Steve. This seems to show no wetting on the Ni on some pads (Passivated Ni?). I couldn't believe it was a pcb problem as the customer said it was only the processor that did not work. I went back to the processor and was able to flick off some balls. I never did like ENIG.................... Thanks again Regards Rex As it is Friday feel free to make this a subject for humour! :-) -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Rex Waygood Sent: 06 November 2009 08:01 To: [log in to unmask] Subject: Re: [TN] BGA Balls Dear All I have a way forward with our customer following the helpful advice received through TechNet and direct from some readers. I am interested in the comments about the datasheet and as someone pointed out there were 24 pages of errata on the data sheet but it did not include Note: It is recommended to apply a soldering temperature higher than 250°C Should read Note: It is recommended to NOT apply a soldering temperature higher than 250°C So we are assuming they really do need 250C Here is another lead free part from Atmel http://www.atmel.com/dyn/resources/prod_documents/doc3438.pdf Page 3 gives 245C max Page 4 gives 235C peak So I don't know how one makes assemblies containing both in mass production process! Regards Rex -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D. Sent: 05 November 2009 18:59 To: [log in to unmask] Subject: Re: [TN] BGA Balls Hi, Werner I could not agree with you more. The process information that is in many component specifications is sometimes so off the wall I can't believe they actually let it get into print. I have seen BGAs that are only available with SAC305 solder balls, but the recommended profile is for standard Sn63, and so on and so forth. Another stated that if the Sn63 BGA is soldered and has any voiding whatsoever it is proof that an unleaded (hotter) profile was used, and the component vendor would not be responsible for any damage that occurred! -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier Sent: Thursday, November 05, 2009 1:46 PM To: [log in to unmask] Subject: Re: [TN] BGA Balls Hi Bob, There is a lot of non-sense put force, and unfortunately, IPC no longer has any reliability experts give workshops on reliability at APEXPO 2010. Werner -----Original Message----- From: Robert Kondner <[log in to unmask]> To: 'TechNet E-Mail Forum' <[log in to unmask]>; 'Werner Engelmaier' <[log in to unmask]> Sent: Wed, Nov 4, 2009 5:51 pm Subject: RE: [TN] BGA Balls Hi, I recall seeing it in the temp specs on the data sheet. It did sound rather low for SAC. I did not see SAC305 called out, not sure what material it was. I would have to go back and double check that data sheet but I swear I saw an above 217 for xxx seconds. I did see the 250 reccomendation and I did see the 260 +0 limit. Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier Sent: Wednesday, November 04, 2009 4:53 PM To: [log in to unmask] Subject: Re: [TN] BGA Balls Hi Bob, Where do you get "were above the 217 minimum" from? 217 is the Solidus of SAC solders-you cannot solder at that temperature because the Liquidus is higher than that and alloy dependent. As an absolute minimum for reflow [unless vapor phase] you need Liquidus+20C at the slowest heating SJ at the BGA center. 'Verifying conductivity' is insufficient, since the latent defect 'head-on-pillow' will give you functionality in a test-and, yes, 5 C can make the difference. Werner -----Original Message----- From: Robert Kondner <[log in to unmask]> To: [log in to unmask] Sent: Wed, Nov 4, 2009 11:54 am Subject: Re: [TN] BGA Balls Rex, Wow, what a you know what contest. :-( They complain about a 5C difference at 250C? Hitting 245 is good IMHO, the absolute max looks like 260. You were above the 217 minimum. Do you have any pin test functions like JTAG or ICT to verify joint conductivity? Testing for manufacturing defects (MDA) using execution of application logic is difficult at best. If they really think there are manufacturing defects (opens, short) I would go for something to verify connectivity parts. If there are many manufacturing defects then you have a process problem. If there are none then it is an application problem. Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Rex Waygood Sent: Wednesday, November 04, 2009 11:36 AM To: [log in to unmask] Subject: [TN] BGA Balls We have built a batch of pcbs for a customer who supplied the pcbs. They are 2mm thick 6 layer with 0.2mm vias and ENIG finish. None work fully, they work intermittently at best. The customer was suspicious that we had not reflowed the BGAs correctly. Our under BGA temp on a similar pcb is 245C (We now have some samples to profile correctly) The customer is suspicious due to the comment on page 753 http://www.atmel.com/dyn/resources/prod_documents/doc6221.pdf <http://www.atmel.com/dyn/resources/prod_documents/doc6221.pdf> where it states a min of 250C Close x-ray evaluation of the BGAs showed tear dropping along tracks, uniform balls, everything looked tickety boo. We offered to remove a BGA to see what was happening underneath. 2 corners showed a similar issue with the ball where it separated from the BGA rather than the pcb. The removal technique was to use a PDR IR rework station, under board heating to bring topside pcb temp to 170C and then a lead free reflow profile to bring the device up to reflow, manual removal. I didn't have dye for dye and pry so thought this might show if there was an ENIG problem. I was surprised by the almost complete removal of ball at the device and lack of evidence of solder. Was this just caused by my investigation processes? Was the ball device interface broken which prevented it from melting the ball? Any other clues? Thanks Rex Hopefully Steve has received the images (sorry about the size!) Rex Waygood Technical Manager Hansatech EMS provides value manufacturing through engineering and quality ________________________________ Hansatech EMS Limited Benson Road Nuffield Industrial Estate Poole Dorset BH17 0RY United Kingdom Tel: Fax: DDI: +44 (0)1202 338200 +44 (0)1202 338202 +44 (0)1202 338222 [log in to unmask] www.HansatechEMS.com <http://www.hansatechems.com/> --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for 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