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Voids - correlation with a not wetting PCB

Vincenzo Longobardo

#13872

Voids - correlation with a not wetting PCB | 11 October, 1998

I have datas to substain that a not wetting PCB ( the HAL oxided or not uniform in thickness )if soldered in reflow, it shows voids with X-Ray inspection.The voids are in side all the joints not only on the solder pads levell.

Is there a technical demostration or correlation between a not wetting PCB and the voids formation ?

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Earl Moon

#13873

Re: Voids - correlation with a not wetting PCB | 12 October, 1998

| I have datas to substain that a not wetting PCB ( the HAL oxided or not uniform in thickness )if soldered in reflow, it shows voids with X-Ray inspection.The voids are in side all the joints not only on the solder pads levell. | | Is there a technical demostration or correlation between a not wetting PCB and the voids formation ? | This has been a very serious issue for many years. To take your initial experiment and findings a step farther, uses X-Sections to see "inside" the void pockets. Then, perform a scanning electron microscopy (SEM) and electron disperssive x-ray (EDX) analysis. The findings will point to cause and demonstrate a direct correlation between oxidation (often excessive tin oxide) and voiding.

I have done this too many times to count and the results are quite graphic and disturbing. If interested I will provide some pretty dirty pictures to show the cause and effect relationships existing in your discovery. Also, I will provide an article about "Controlling the Uncontrollable Hasl Process."

Another finding you might make with this analysis is the presences of residual flux components. They often are left within the voids as they continue fighting to remove the excessive oxidation.

I have other pictures showing excessively oxidized leads. Some have as much as 18:1 surface oxide to metal ratios. This, in combination with oxidized HASL surface conditions, provides even more interesting failure mechanism. It also is surprising how much of this type thing exists today even as we advance to no clean and beyond while still not having come up with suitable alternative solder termination area coatings assuring a shot at solderability.

Your discovery is not new. It is, however, one that more people ought to see for themselves - up close and in person.

Your can run more tests and discover a direct correlation between voiding amounts (percentages, numbers, size, location types, etc.) and varying cycles to failure using thermal and mechanical stress testing.

Earl Moon

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Vincenzo Longobardo

#13874

Re: Voids - correlation with a not wetting PCB | 13 October, 1998

Dear Mr. Earl Moon please give me all your information and pictures to know the reason of the voids formation caused by the HASL oxidation. I am very interested to this experience.

With Best Regards V.Longobardo |

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Earl Moon

#13875

Re: Voids - correlation with a not wetting PCB | 14 October, 1998

| Dear Mr. Earl Moon | please give me all your information and pictures to know the reason of the voids formation caused by the HASL oxidation. | I am very interested to this experience. | | With Best Regards | V.Longobardo | | | | I will assemble the information and graphics over the weekend and email you after.

Regards,

Earl Moon |

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