Sorry, Daan. All contamination on incoming components is undesirable, no
matter the process. It may a) interfere with the solderability of the
leads; b) depending on the nature of the contamination and the cleaning
process, remain on the assembly untouched; c) upset the flux chemistry;
d) osmotically penetrate the component body or otherwise bond thereto;
e) etc.

I've never excused component manufacturers (including PCB manufacturers)
from their obligations to provide clean components: in any case, how
does a ceramic capacitor maker know whether a component will be cleaned
or not and, if so, how and in what product? If they cannot provide clean
components, they should go out of business. Tuff!!!

Brian

d. terstegge wrote:

> Hi Brian,
>
> I understood from earlier posting of you and others that the lack of
> cleanliness of incoming components is considered a risk ONLY for
> no-clean technology.  Now Cheryl obviously has a problem with
> contaminated parts in a process that does include cleaning. This makes
> me wonder how (in general) the chances are that a cleaning process
> designed mainly for cleaning flux residues from pcb assemblies will
> clean the variety of contaminants present on incoming parts. Perhaps you
> can comment on this ?
>
> Daan Terstegge
> Thales Communications
> Unclassified mail
> Personal Website: http://www.smtinfo.net
>
>
>>>>[log in to unmask] 02/11/04 08:56am >>>
>
> Amen! Lord Doug has hit it on the head.
>
> It may interest you (academically) to know that the erstwhile company
> I
> owned manufactured the Microcontaminometer 20 years ago, through to
> 1991. It was capable of measuring the ionic contamination on parts as
> small as a single diode. It was not a popular instrument: I think we
> probably sold less than 50 of the beasts. What we did find was that
> many
> components were hopelessly badly contaminated. There is a whole
> chapter
> in my book on this subject, with photos. One IC, which is shown,
> measured at 12.4 µg/cm2 eq. NaCl and this is by no means exceptional.
>
> My experience in my former professional life was that component
> manufacturers cared even less about cleanliness than they did about
> solderability and I know no reason why this state of affairs should be
> any different today.
>
> Brian
>
> Cheryl Tulkoff wrote:
>
>
>>I've been working on a tough but challenging contamination problem.
>
> The
>
>>contamination causes electrical leakage fails on a precision test
>>instrument. Ion chromatography analysis points to an incoming
>
> cleanliness
>
>>problem on a SOT-23 component. Elevated choride and sulfate levels
>
> were
>
>>found on the components (5x - 10x greater ug/in2 levels than
>
> anything
>
>>found elsewhere on the boards). High levels were found even on our
>
> "good"
>
>>boards.
>>
>>We are trying to work with our supplier to identify and fix the
>
> problem
>
>>long term but are looking for some short term fixes as well.
>
> Repeated
>
>>water washing of the boards (high pressure spray cleaning) improves
>
> the
>
>>situation but does not fix it. Alcohol scrubs in the area further
>
> improve
>
>>it but don't eliminate the problem entirely.
>>
>>We have a only a DI water wash process (no surfactant/saponifier
>>capability).Does anyone have any board or component cleaning
>>recommendations?
>>
>>Are there any parts makers out there willing to tell me a little
>
> more
>
>>about parts cleaning after the lead plating process?
>>
>>What tool(s) do part makers use to verify cleanliness of parts?
>>
>>I don't have a tool capable of measuring what was found on the part
>
> so I
>
>>don't know where to go.
>>
>>Thanks, Cheryl Tulkoff
>>
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