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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Werner Engelmaier <[log in to unmask]>
Date:
Fri, 6 Nov 2009 19:14:01 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (972 lines)
 H Dave,
You misread my reply—I did not ask a question.
Werner

 

 

-----Original Message-----
From: [log in to unmask]
To: TechNet E-Mail Forum <[log in to unmask]>; Werner Engelmaier <[log in to unmask]>
Cc: [log in to unmask]
Sent: Fri, Nov 6, 2009 6:35 pm
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/>;  

 



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