Joyce

100% agree: your statement should go into the Bible as the 11th Commandment!

Let me recount two anecdotes, coincidentally both regarding Kovar leads. 
One place I visited used a commercial ZnCl2/HCl flux for tinning them, 
followed by a thorough three-phase wash/DI rinse process. I tested their 
components, very low ionics on them and AFAIK no customer complaints re 
corrosion. The second one was a company making DIL components with a 
Kovar lead frame. At the end of the line, they placed the components 
into a titanium sheet which was perforated with holes at 0.1" pitch, I 
guess about 500/sheet. This sheet was then passed through a conventional 
wave soldering machine using a well-known W/S flux which was bright pink 
(need I say more?) and then directly hot air blasted and (hopefully) 
water washed. The problem was that water barely flowed through the holes 
in the titanium sheet (from memory about 1.5 mm thick) and flux residues 
remained on the shoulders of the leads. If you happen to have a copy of 
my book, see Fig. 8.1 (a) for the results.

Therefore Commandment #12: Thou shalt thoroughly deflux all components 
after hot tinning, applying solder balls etc.

Brian

On 19.02.2014 17:47, Joyce Koo wrote:
> The danger of extraction of no-clean flux parts is inconsistency: if the parts has been in storage for long time, the extractable are not readily testable in short time (diffusion driven.. need to go through the skin of the oxidized flux surface).  Thou shall not use no-clean for intermediate process, such as components.
>
> Joyce Koo
> Researcher
> Materials Interconnect Lab
> Office: (519) 888-7465 79945
> BlackBerry: (226) 220-4760
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Larry Dzaugis
> Sent: Wednesday, February 19, 2014 10:13 AM
> To: [log in to unmask]
> Subject: Re: [TN] Cleanliness testing at component level
>
>   One IC manufacturer used a no clean flux on the components in its vented BGA package.
> This was fine for the majority of its customers using a no clean process.
>
> Cleaning the package was interesting as the Govt requirement was di water, the customer used a chemistry and would not provide a wavier.
> It was an airborne device.
>
> It was only after there were test failures were the various conflicting reports pulled out and received from the customer, supplier and agency.
> An incoming spec would have helped.
>
> Larry Dzaugis
>
>
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