minor voiding actually are good for solder joints (a old old story - provide it is uniform and small and not that many and round). not sure if there is any digital record... early 90 and late 80 stuff. Am I dated myself? OMG... jk On May 11, 2015, at 6:23 PM, Wayne Thayer wrote: > Practically, XRAYS are used to measure voiding since that is > non-destructive. The XRAYS used are uni-directional, so they > basically have > no clue as to vertical position of a void: They only allow you to > estimate > areas where there is less mass for the XRAYS to interact with. > Hence we use > area. (And this seems adequate also!) Since the XRAYS are good > detectors of > missing material, what is called "area" is really something about > missing > mass. In fact, if the actual void is 2 microns tall and occupies > 95% of the > area on a joint, the XRAYS just plain don't see it at all. > > Wayne Thayer > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo > Sent: Monday, May 11, 2015 4:32 PM > To: [log in to unmask] > Subject: Re: [TN] Voiding evaluation > > it is all depend upon what kind of stress - temp cycle most likely > you have > experience shear load, vib and impact are different, pending on > direction (6 > faces, x-edge, y corner, etc.). strain rate also place the role. > voiding > can not be a uniform acceptable criteria... it is all depend upon > how much > design margin allow. (we can see the cow go home...) > jk >> If the criterion was the evaluation of the ratio load/area, one >> should >> sum only the void areas that lie on a same plane (perpendicular to >> the >> load), >> >> For example, if the direction of the load is vertical, the areas of >> voids placed on higher or lower planes shouldn't be summed, because >> the solder joint area which bears the load in each plane depends on >> the voids intersected by that plane, not on the voids placed >> higher or >> lower in the solder joints. >> >> Since the sum is extended to the entire volume of the solder joint, >> the criterion would seem another one. >> >> Enrico >> >> Il 08/05/2015 15.55, Ed Hare ha scritto: >>> I would suggest that the area criterion is appropriate since >>> stress = >>> load/area. It is not a missing mas issue in my opinion, it is a >>> reduction in load bearing area that is of concern. >>> >>> Ed Hare >>> VP SEM Lab, Inc. >>> www.semlab.com <http://www.semlab.com> >>> >>> On Fri, May 8, 2015 at 5:15 AM, Enrico Galbiati >>> <[log in to unmask] <mailto:[log in to unmask]>> >>> wrote: >>> >>> I would like to ask anyone if there are any reliability data >>> regarding the evaluation of voiding in a solder ball (BGA). >>> >>> In both the standards IPC-7095C and IPC-A-610F, the voiding >>> in the >>> solder balls is evaluated measuring the area of the voids. >>> However, the weakening of balls caused by voiding should >>> depend on >>> the amount of the missing material caused by the presence of >>> voids. If this is true, the amount of the missing material >>> should >>> be measured by the total *volume* of voids, not by the area. >>> Consequently, the limit should be set on the volume, instead of >>> the area. >>> >>> For example, with the present rule based on the percentage of >>> area >>> of the voids, a solder ball of 0,85 mm diameter, with a single >>> void of 0,45 mm diameter, is acceptable, since the percentage of >>> voiding is 28%, thus less than the maximum limit of 30% (ref. >>> IPC-A-610F). In this case, the missing volume of the material is >>> 15%. >>> >>> Considering another example, if a solder ball has 6 voids of a >>> 0,20 mm diameter each, giving 33% of the area of voiding, >>> would be >>> rejected. However, in this last case the percentage of the >>> missing >>> volume is only 8%, i.e. less than the previous case (about >>> 53% of >>> the previous case!). >>> >>> So, the ball of the second case is rejected, even if it stronger >>> that the one of the first case. On the contrary, it is the >>> solder >>> ball of the first case that should be rejected. >>> >>> Enrico >>> >>> -- >>> Enrico Galbiati >>> Consulenza Affidabilità e Normative >>> Via Kennedy Ingresso 2, 20871 Vimercate (MB) - Italy >>> Desk: +39.039.8908.4547 <tel:%2B39.039.8908.4547> - Fax: >>> +39.039.8908.5051 <tel:%2B39.039.8908.5051> - Mobile: +39.335 >>> 6833616 <tel:%2B39.335%206833616> >>> E-Mail:[log in to unmask] >>> >>> >>> >>> > ______________________________________________________________________ >>> This email has been scanned by the Symantec Email Security.cloud >>> service. >>> For more information please contact helpdesk at x2960 or >>> [log in to unmask] <mailto:[log in to unmask]> >>> >>> ____________________________________________________________________ >>> _ >>> _ >>> >>> >>> >>> >>> -- >>> Ed Hare >>> gmail - [log in to unmask] <mailto:[log in to unmask]> gvoice - >>> 360-453-7550 >> >> -- >> Enrico Galbiati >> Consulenza Affidabilità e Normative >> Via Kennedy Ingresso 2, 20871 Vimercate (MB) - Italy >> Desk: +39.039.8908.4547 - Fax: +39.039.8908.5051 - Mobile: +39.335 >> 6833616 E-Mail:[log in to unmask] >> >> >> >> _____________________________________________________________________ >> _ >> This email has been scanned by the Symantec Email Security.cloud >> service. >> For more information please contact helpdesk at x2960 or >> [log in to unmask] >> _____________________________________________________________________ >> _ >> > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud > service. > For more information please contact helpdesk at x2960 or > [log in to unmask] > ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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