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Solder paste normalisation period



Solder paste normalisation period | 16 August, 2001

I've carried out an experiment on the solder paste normalisations upon withdrawal from refrigerator, by probing a few thermocouples onto the jar and syringe and let in normalise in room temperature for 6 hours ( using the temperature profiler ). The supplier calls for 4 hours normalisations, but I found out that the solder paste has reached it's room temperature at after 1.5 hours. Is there any reasons chemically, why the supplier wants it to be 4 hours. Are they chicken out ?

Is there any reference document that writes about the same experiments with what I did ?


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Solder paste normalisation period | 16 August, 2001

Hi Dan,

Did the manufacturer specify the temp at which to store your paste? You could be 20 degrees apart from each other. Plus, room temperture to you may be 74 degrees F, while to a hard nose owner who doesn't like heating his building, it could be 54 degrees in the wiinter. I think they know that about an hour and a half is a reasonable time, but probably double it just to make sure. Besides, we're getting paid the big bucks to design our own processes, this being part of one!

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Solder paste normalisation period | 16 August, 2001

Interesting Dano.

Tell us more about the variables in your experiment, please.

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Solder paste normalisation period | 17 August, 2001

Thanx Dave/Hussman..

We normally store our solder paste in the refrigerator at 0-10 Deg C as per what the supplier recommanded. Our floor temperature is controlled at 22 +/- 5 Deg C and Humidity is at 55 +/- 5%. Recently we have customer asking for 0 - 7 Deg C ( I don't know why ? ). Anyway, FYI, I'm in Malaysia, so it's hot thru'-out the year.

Here is the details of the experiments. On the jar that is fulled of fresh paste taken out from the refrigerator, I've made a small holes (about 4 of them), lining from the top to the bottom of the jar. I sealed the holes with the kapton tape, then kept the jar back to the refrigerator and leave it for more than 4 hrs. i.e. to simulate the actual withdrawal temperature.

Upon withdrawal, I took out the tape and probe the holes with thermocouple ( push it to the center i.e to measure the temp. at the center of the jar ) which is connected to the Temperature profile and leave it at the shop floor at where the paste is normally being normalised for about 6 hours.

I've just joint this company for about seven months and trying to removed whatever non-value add been practice from the floor. I planned to remove the spinning process which uses the solder paste softener. So I did the above experiment on both spin and w/o spin just to see the effect on normalisations. They found out to be normalised at the same time frame which is at about 1.5 hours.

Any comments on the experiment guys !!!..input are welcome.

Opps Dave!! remember the old datecode PCBs that I was asking you about ? I was forced to use the boards, well, I said O-rite. provided you guys don't count the rejects in my yield report ( since I'm measured from my yield report ). As he claims ' NO RISK NO GAIN "..well, You are the Boss, so what the heck!! before that, I 've printed the paste onto the PCB and got them reflowed, 10 out of 10 gave me a good wetting/solderability. So, I said " win". But I've insisted them to bake the board prior using it. since they came in a loose form ( you dont want to know details..). My Boss said,.. No Danial, you gotta be crazy, don't you know that this is ENTEK finished, if you bake them you gonna spoil them...

My question here is will it cause any problem on solderability if we bake at 100 Deg c for 6 hours? Did I make a mistake here? My Boss may have his point but I also have mine...moiture entrapment/delamination etc....question, should the ENTEK layer will only give ways when the flux comes into contact with the pad and the holes ?

Looking forward for you answer guys!!! Thanx...and have a nice weekend. thanx..

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Solder paste normalisation period - Baking Entek | 17 August, 2001

We knew they�d make you use those boards, didn�t we?

Your boss could be correct, but then again, you might get away with baking. Entek coating thickness is often poorly controlled by fabricators.

But if sample boards that you ran are OK, why not go for it? Plus it'll puff-up your boss and get him to thinking that he knows what he's talking about. Oooo, that could be damgerous.

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Solder paste normalisation period | 19 August, 2001

Yano, imalookinat two vendor specification sheets that say your paste should sit around at "print temperature" for 1 to 6 hours before printing [er, words to that effect].

Werejallgit this 6 hours stuff from?

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Solder paste normalisation period | 21 August, 2001

6 hours is just the figure I plugged from the sky. U-no-whak, this company used to follow 8 hours religiously in the past..scary huh!!!


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Solder paste normalisation period - Baking Entek | 23 August, 2001

Hello... that last paragraph reply, makes one sound like, Dilbert De Engineer.....

Beware the pointy haired guy...

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