Oh how I agree with this comment.
Everything I've found so far says joint reliability with no voids is worse than some voiding. The joint reliability does not fall off catastrophically when the void size is 1% over what is permitted in IPC-610. Therefore spurious accuracy is the pursuit of those who have nothing better to do or want to justify a bigger and better toy.
The X-Ray machine is useful in process control, yesterday I had a few small voids, today I have a lot of big ones, something has changed and should be investigated. IPC 610 seems to me to give about the right amount of weight and concern on voiding.
Regards
Rex
Rex Waygood
Technical Manager
PartnerTech Poole Ltd
Benson Road
Poole
Dorset BH17 0RY
United Kingdom
Tel: +44 (0)1202 674333
Fax: +44 (0)1202 678028
DDI: +44 (0)1202 338222
Mob: +44 (0)7887 997403
[log in to unmask]
www.PartnerTech.co.uk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: 10 September 2008 14:18
To: [log in to unmask]
Subject: Re: [TN] precise void size measurement
Bonjour Fabrice,
Problem number one with voids measuring is how you know when you have the real void size on the screen. On many machines the size of the voids depends on the energy you shoot at the board; the higher the energy, the bigger the void image.
So what is the optimal energy for seeing the real size of the voids? You might need to work this out with your machine manufacturer. The Glenbrook Jewel Box we have does not seem to be affected by that, the voids don't really change size when varying the energy.
Now that I raised a question instead of giving you an answer, I would like to be even more confusing: why do you want to complicate your life opening this voiding can of worms? It is a never-ending story and you are privileged, being part of an OEM, so you don't have to go through this hassle. Why privileged? Because you can define what you can accept in terms of voids, regardless the existing industry specifications. According to past threads on Technet nobody could bring an example of BGAs that failed because of voiding, so I would say that you should ESS boards with as big voids as you can get and see whether voiding can be an issue for your products.
Being in the CEM business I can tell you that voids measuring is prone to very subjective interpretations. If you can eliminate this concern, you will be happier.
Regards,
Ioan
-----Message d'origine-----
De : fabrice pires [mailto:[log in to unmask]]
Envoyé : 10 septembre 2008 08:40
À : [log in to unmask]
Objet : Re: [TN] precise void size measurement
Alan,
I guess these ball bearings helped you to test image quality of tested equipment and calibrate the Xray equipment to define size of BGA balls and other things.
But do you thing metal balls can be used as precise calibration for measurement of voids inside BGA balls?
I mean voids are lack of material and balls are presence of material (metal).
In other way, does the equipment setups for correct observation of ball bearings is really the same for the voids observation and size measurement?
Thanks in advance for your input.
Fabrice
Alan Kreplick a écrit :
> Fabrice,
>
> When I was evaluating X-Ray equipment, I brought precision ball
> bearings (I think they were .050").
>
> Each machine had some sort of measurement tool, but no matter the
> machine or changing focus, tilting 50-75 degrees, etc., the .050" ball
> bearing was my benchmark.
>
> To stop the ball bearing from rolling around on the table or assembly,
> I glued it to a small piece of conductive composite material
> (left-over wave solder fixture stock).
>
>
> Al Kreplick
> Sr. Manufacturing Engineer
> Circuit Card Assembly
> Air-toAir/Precision Strike/Land Combat Raytheon Integrated Defense
> Systems 978-470-9931office
> 978-245-1702 pager
> 978-470-4307 fax
> [log in to unmask]
>
>
>
> fabrice pires <[log in to unmask]> Sent by: TechNet
> <[log in to unmask]>
> 09/09/2008 11:01 AM
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to fabrice
> pires <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> [TN] precise void size measurement
>
>
>
>
>
>
> Hi Techneters,
>
> I would like your advices on the best way to calibrate XRay pictures
> in aim to measure precisely voids inside BGA balls, after assembly.
> Everyone should agree on the fact slight setup variation on XR
> equipment could change significantly the void size results.
>
> Do you have any trick to improve precision measures whatever the XR
> equipment?
> Does the use of any reference/calibration on boards exists in that aim?
>
> Fabrice
>
-------------------------------------------------------------------------------
The information contained within this e-mail and any attachments contained therein may be confidential and/or legally privileged and is for the use of the intended recipient only. If you are not the intended recipient please delete it from your system and notify the sender by return e-mail. The content of this e-mail may not be copied or disclosed to any third parties without prior permission from the sender.
E-mail is susceptible to data corruption, interception, tampering and viruses. We do not accept any liability for any such incidents or any consequences thereof.
---------------------------------------------------
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 additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
