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Necessity of ROSE in commercial quality processes

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#40017

Necessity of ROSE in commercial quality processes | 26 February, 2006

Hi,

We will run a no-clean wave solder process to assemble TV boards. What about incorporating a ROSE Test equipment (Ionograph, zero-ion, Omega Meter) in the process? Is it recommended, helpful or unnecessary?

I�ve read about the use and limits of ROSE on the web, but what I really need is a practical assessment of its advantages in commercial-quality application like ours.

Thanks in advance for your help�

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GS

#40018

Necessity of ROSE in commercial quality processes | 26 February, 2006

Hi,

just my comment, theoretically No Clean means no Ion Contaminants from Flux, but it some some case ion contamination (Cl-Br-F) could come out from raw PCBs, from Components, from fingerprints, etc.

To incorporate a ROSE step in the process it could tell you some thing but in my experience I never seen to use it on a NC process, just some trial.

Other comment, as you know the blend liquid used for ROSE contains DI water and IPAlcohol, so after running ROSE test the PBA gets out from cell with white residuals or strange colors on PCB surface. This is due to IPA who dilutes the NC flux residues left by solder paste or flux residues left by wave solder or manual soldering, ecc. It is not so good to see as a cosmetic point of view.

Regards.................GS

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Mike Konrad

#40019

Necessity of ROSE in commercial quality processes | 26 February, 2006

Hi GS,

Just a clarification� No-clean does NOT equal no ions. It equals less ions (at best). Automatic R.O.S.E (Resistivity Of Solvent Extract) testers are commonly used to detect ionic contamination from no-clean applications. Your comment regarding white residue after testing illustrates the degree of �invisible� contamination on a no-clean assembly. The IPA /DI water test solution does not cause residue rather it makes the no-clean residue visible.

If one is to use an automatic ROSE tester to determine cleanliness, I would recommend that one choose a system utilizing �dynamic� technology over �static� technology. Dynamic testers (Zero-Ion and Ionograph) utilize a dynamic method which improves the detection of weak ions associated with no-clean fluxes.

I hope this helps.

Mike Konrad

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#40029

Necessity of ROSE in commercial quality processes | 27 February, 2006

Hi,

Thank you for your answers. But I want to explain some points on which I would appreciate any comment: * Having calibrated the process, we intend to carry out the ROSE test just on SAMPLES of the finished boards. Lets say one every hour. I expect this would help us detecting high ion contamination caused by an eventual bias in some process parameters, or maybe accumulated contaminations in the solder pot.

* I know that ROSE testers are commonly used in military, high quality and RF PCB assembling. Some times this is done in conjunction with other methods such as SIR and ion chromatography. Our application is just COMMERCIAL QUALITY TV CHASSIS, and what I�m wondering about is: 1- Are these tests used for this range of applications? 2- Do TV applications (being a consumer domestic product) tolerate some ion residue in such a way that we can disregard ion tests? 3- Should we worry about ion contamination (for our application) if we use a good machine using a spray fluxer, a good flux, and process parameters satisfying flux requirements?

I hope I�ve made it clear, and I hope I�ll get your help that I�ll appreciate much.

Regards,

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GS

#40038

Necessity of ROSE in commercial quality processes | 27 February, 2006

Thanks Mike, you are correct.

According to Flux designation we could have some residual of ions on PCB/PBA.

My experience was mainly by using Omegameter SMD-600 (automatic and dynamic ROSE)on samples to detect TIC (Total Ionic Contamination) after PBA wash off process. PBA soldered by Clean water soluble: Paste and Wave Fluxes .

TIC contamination level max 1,56 ug/cm2 NaCl equivalent as for ie. IPC-JSTD-001... or 0,5 ugr/cm2 in case of PBA coated by Conforma Coating IPC-AC-62A

Well, we had several contamination troubles due to Connectors (> 3,5 ugr/cm2 NaCl) or power components, or Raw PCB. Nothing with the solder process or fluxes. Ion Chromatography analysis was necessary to help understanding of contamination origin.

When occasionally we run TIC on a NC assembled PBA (Paste ROL0 or L1) after 10 minutes duration Test by Omegameter (IPA/DI water media at 45�C), even if TIC value was in the specs, the removed PBAs from Omegameter, have plenty of white residuals that in order to have a reasonable cosmetic aspect we used to deeply brush away the residuals from PBA. Other problem met, during and after test plenty of floating "stuff" in the media, requiring so often media filtration cycles with a risk to clog the filters(Mix Bed).

Our NC assembly Process (SMT and Wave) does not include TIC test after assembly.

In our processes, TIC test is a must as an SPC step, only for PBA soldered by Clean Process (WS Paste and WS flux).

To MASRI I do not have experience on PBA for TV products or similar. My suggestion could be, if you are really sure about your wave solder process is well set up, you should not worry but if you want to be sure and, if you have available an automatic tester (brands like above mentioned)or by mean of external Lab, try to run some TIC test on samples like a process validation.

After test results are in your hands you can decide how to proceed as a final solution for your process.

To have an automatic TIC tester on the floor and perform tests like you think once by hour it is a costly operation. So before to decide for it, do the right assessments.

Best Regards........GS

Sorry for my poor English.

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#40039

Necessity of ROSE in commercial quality processes | 27 February, 2006

I'm not sure that would be valid. My understanding was that solids were trapped by other non-active flux residue. Which is why you can leave them on and why you see white residue after washing. I think the ROSE test would release particles that would not otherwise be released. And therefore your sample would be different from the rest of the run.

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#40070

Necessity of ROSE in commercial quality processes | 28 February, 2006

As I know, the encapsulation effect occurs only with rosin based fluxes. So if you have a PBA soldered using RA Flux, you should either wash it well, or leave it alone and it will be safe.

For NC process the story is different because there�s no resin structure to trap activators. So when you see white residue it�s one of two: 1- Crystallized organic acid that have been left without reaction or burning off. This is the harmful residue that we lute to avoid by good process control. It�s highly soluble, and therefore will be dissolved in the test solution and will contribute in its conductivity. 2- Organic salt formed by the reaction between the organic acid activator and tin or lead oxides. This kind is benign and can not be removed with water.

I think that the washing operation done during ROSE dissolves and measures the first type while (somehow) showing up the second type.

Thanks to all, and I hope I get more comments especially from those having real-life experience in TV assembling.

Regards,

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KEN

#40143

Necessity of ROSE in commercial quality processes | 2 March, 2006

I recently finished analysis of no-clean fluxes and Ionic contamination and cleaning processes. The results were eye opening. Summary: If you clean a no-clean you better do a good job.

Many no-cleans produce a "waxy binder" to encapsulate the troublesome ions. Identical process as in the old RMA days. No difference. If you didn't clean an RMA then why clean a no-clean now?

I would: Use BELCORE certified, halogen free materials, verify your thermal process for no-cleans (good profile), control you flux application process (only apply what you need) and not ROSE test for ionics.

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