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Non-wetting on 0402 chips capacitors

zam_bri

#6534

Non-wetting on 0402 chips capacitors | 9 May, 2001

Hi..

Recently, I have received a few reels of 0402 with an old date code ( but still less than 2 years old).I don't have a capability in-house to carry out the solderability test except for the dipping test ( dip the components in the molten solder in the mini pot). From the Dipping test, all the 0402 components seems to show an "OK" wetting. It is very difficult to justify this to material's group when I have all the components passed the dipping test. The fact is that when running them in mass-pro mode, the result seems to be disasterous as the PPM reaches 40 000, where 99.5% came from non-wetting at 0402s' terminal. Very similar to Tomb Stoning problem but more towards non-wetting ( I saw the sign of oxidation on the terminal, when the components sits flat but no connection). I'm not sure whether dipping test is the right method or not, in order to check the solderibility of the components. While putting the blame onto the components, deep down I'm seriously worry about " what if my process is actually the culprit".

From my side, I've optimised my profile to the minimal heat exposure in order to avoid oxidation at preheat/reflow. Pls let me know whatelse should I do.

Thank you in advance.

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CAL

#6535

Non-wetting on 0402 chips capacitors | 9 May, 2001

Your process needs some refining. How long did it take to wet? How much force did it take to break the surface tension? What type of solder was in the solder pot? What type of flux was used? What was the pot temperature? Did you take a cap and put it in hydrogen peroxide to accelerate the aging and compare the results? Was the bag the components in sealed?

Did you down load our Jan 01 empfasis article on Solderability (www.empf.org)?

ZAM_BRI we need a little more info.

I am here for ya!!!

Caldon W. Driscoll ACI USA 610-362-1200 cdriscoll@aciusa.org

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#6537

Non-wetting on 0402 chips capacitors | 9 May, 2001

Awww, don beso tuff on ursef!!!

It sounds like you�re thinking correctly with what you�ve done, but it�s possible that the test you ran did not represent your actual production environment as well as you would have liked. So, you just need to "crank it up a notch", as Eniril says. In doing that, consider this:

1 Run a white ceramic (high purity aluminum oxide) substrate through the reflow oven.

2 Allow the substrate to cool.

3 Print solder paste onto a ceramic substrate in the shape of 0402 pads, using your routine paste, methods, spacing, etc.

4 Place components from both the "old date code" reel and a "more current date code" reel in the paste as you would place components in standard production. Keep track of the components from the two sources. [Just put finger nail polish on the body of certain components or something like that.]

5 Reflow solder the ceramic substrate using the paste manufacturer�s recommended profile.

6 Inspect the solder fillet at X10 magnification.

7 Describe the fillet and the number and size of the solder balls. Ideally, the solder fillets exhibit acceptable attributes as smooth, usually shiny, clearly defined, well feathered (small contact angle), completely wetted metallic bonds between metal surface of the component termination and the solder and there should be no solder balls.

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zam_bri

#6542

Non-wetting on 0402 chips capacitors | 10 May, 2001

Hi Cal/Dave F,

Good news today. The problem went away when I received and ran with a brand new component today. But I'm sure with a robust profile, I should be able to compensate oxidations at some degrees, rite? ( taking into consideration the successful rate when the said components touched up with a soldering iron). What is the typical shelf life for Chip capacitor & Res ?

Anyway, below are answers for CAL's questions:

1) Time to wet...ehmmm!! time to reach 183 Deg C ? it is about 3.2 mins. 2) How much force ? how do I measure that. 3) Type of solder..normal euthatic 4) No flux were used when doing the dipping 5) Pot Temperature was measured at 254 Deg C. 6) Take a cap and put it in hydrogen peroxide to accelerate the aging and compare the results...will do this, will have to source for the hydrogen peroxide. 7) Components was not sealed.

I remember asking this question, what is the typical shelf life for Chip capacitor & Res ? I have set 1 year as a limit...what do you guys think.

Thank you for your help. It was much appreciated.

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#6543

Non-wetting on 0402 chips capacitors | 10 May, 2001

It depends ... * Components stored in a garage in Chiriqui,Panama will have a different shelf life than those store in a climate controlled room in Ayrshire, Scotland. * Components from a reputable supplier will likely have a different shelf life than those from Blackie's Good As New ... and on and on.

We don't like to store components. Usually, the money our buyer saves by buying by the truckload is lost by 10X when the poor saps in production have to process those wonderful parts. [So, the buyer gets a bonus for saving money and the production guy gets fired because he can't solder the fine parts. Hmmm.]

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