Fillet Tearing

I like the "if you can see the bottom" part! would that include Xray inspection?

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WEll Im hearing all this talk about leadfree nonsense from the engineering dept at my place of employment.Let me tell you Ive been looking at this stuff for 12 yrs and i think tearing of the filet is a normal part of the solder joint kindof like dross.everyones all worried about dross and such but i feel its the nature of the beast with wave solder.our second shift inspectors have eyes like hawks and they always seem to catch this stuff.same goes for those gull-leads that our ai dept places on the board.our inspectors seems to catch those as well.those gulled parts have a wrinkly appearnce but that has more todo with bad profiling.Again as i mentioned in another post Im acutualy looking to branch out in more of a consulting role.It seems like my threads that i post here seem to make alot of you less expereinced folks scratch their heads which is why i thought about this consulting thing.seems not enough of you think outside the box like me.Ill be posting more frequently in the future to all matters wave related and if anyones intrestid in my consutlation i can be emailed at WaveMasterLarry@yahoo.com i understand theres another fella here who has a website for consulting too and if he can do it why not me too?

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Dear all,

Referring comment from Mr. Jack,IPC director certification & assembly technology, the term "fillet tearing" is too broad. Cracks or fractures in the required fillet area, with SnPb or LF alloy and whether you call it tearing or not, is a DEFECT. For lead free alloy in PTH connection "hot tear" that isn't in the required fillet area (next to lead or land) is identified by 610D as Acceptable. Analysis has shown that this tearing affect is nearly always in a copper-rich area of the alloy. Remember that LF solder used for wave soldering is usually about 99.3% Sn and 0.7% Cu. It is hard to keep that very small amount of copper evenly dispersed through the molten tin and sometimes a "clump" of copper molecules will accumulate. Sometimes after processing a lot of PCBs the Cu level in the wave bath increases because of Cu washing or scrubbing from the PCB conductors into the bath. An intermetallic region will form around these Cu molecules and hot tear may occur in between that intermetallic and the copper molecules. As a separate issue, again specific to LF alloys in PTH holes, an anomaly can occur when there are large mass, thick lead through-hole components. Often the preheat process has to be set very high and as a result, these large mass components are much slower to cool down after passing over the wave. The thermal energy in the component and lead means that the thin solder at the edge of the land freezes slower than the solder in next to the lead in the middle of the hole. As it is cooling towards the point it will freeze, it is shrinking in size and the surface tension creates a lot of "pull" stress on the solidified solder on the edges. Depending on all the physics involved, sometimes there is so much stress that the solder pulls away from the copper land around the outside edges. This is called fillet lift. On analysis, it has been determined that this fillet lift always occurs between the intermetallic and the copper land. If there are other conditions that would cause the land to separate, the acceptance criteria is completely different (Chapter 10 of IPC-A-610D). So he mentioned that our customer is correct that 610D has criteria for Hot Tear, but there is no other criteria that would permit acceptance of damage in the required fillet areas, regardless of the type of alloy. He believe the term "fillet tearing" may have meaning only to the person that wrote the Vitronics article but it wasn't used by any of the several hundred members of the 610 or J-STD-001 committees.

So, anybody has any further comment ?

Best regards,

Joseph

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