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Is NO CLEAN any better for High Speed PCB's?

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#73131

Is NO CLEAN any better for High Speed PCB's? | 20 November, 2014

Hi All,

I have a customer with a very dense design (24 layers, 0201's lots of micro-BGA and lead-less), and they run extreme data rates.

Every once and a while they will have a unit that has some speed fall off and they attribute that to the possibility of contamination being trapped under a lead-less power supply, and causing some impedance changes in the high speed data line.

Currently the assemblies are run with water soluble organic flux and cleaned multiple times during the process with an aquastorm with the hurricane option and di-water. We are confident that the cleaning that is done is as good as can be done with water soluble flux.

The customer is pushing us to try using No-Clean as a possible solution to the impedance changes they sometimes see.

We tend to run no-clean on high volume, simple products that run and are shipped with little fuss. I don't have a lot of experience with using no-clean with dense products, covered with micro-BGAs and 0201's.

Can anyone share an opinion on the possible benefit or issues with using a no-clean on dense assemblies and if there may or may not be affects or benefits to doing so on high data rate designs. Part of my concern is that if they think there may be contamination causing an impedance change that the amount of residue left with No-Clean may be even more.

Any insight is most appreciated. thanks

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#73132

Is NO CLEAN any better for High Speed PCB's? | 20 November, 2014

If they asked you should try it?

Im really interested in the outcome in general.

We use no clean on 6 layer multi micro-BGA boards, chip size only goes as small as 0603 though. Around ~500 parts over a 4"x3" area. we haven't noticed any independence problems..then again we might not be high speed enough.

Hope you can provide an update with any findings!

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#73179

Is NO CLEAN any better for High Speed PCB's? | 1 December, 2014

adam, could you write the name of solder paste, which you use for this applications? thx!

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#73184

Is NO CLEAN any better for High Speed PCB's? | 2 December, 2014

A trick I used to use doing RF design was to have on the edge of a panel, a stripline that I could hook up to a Network Analyser to check board impedance. You could do this to verify if the fault is in the no wash process or a board manufacture processing issue, like track width on etching or variation in di-eletric constant in your fiberglass.

regards sarason

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#73207

Is NO CLEAN any better for High Speed PCB's? | 9 December, 2014

SAC305 (Alpha OM - 338 PT) (88.5%) T3

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#73255

Is NO CLEAN any better for High Speed PCB's? | 21 December, 2014

oh we also immersion silver finish our PCB's.

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#73351

Is NO CLEAN any better for High Speed PCB's? | 17 January, 2015

If you have a SPI machine you could try it, I have used no clean on some products, it is okay, depending on the product. Maybe the best way is to have SPI with feedback function to the printer and only when, for example, volume is above 220% to clean the stencil.

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nvn

#73372

Is NO CLEAN any better for High Speed PCB's? | 21 January, 2015

Hi, Wow…thank you for this awesome post. It really shows your immense knowledge and research on this topic. Please keep sharing.

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Reflow Oven