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Is there any good articles to read on solder paste?

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#69075

Is there any good articles to read on solder paste? | 27 May, 2013

Is there any good articles to read on solder paste? (just to see if I may of missed something)

Sometimes I can not believe the people I have to work with. We had a panel with two “Quad Flat Package” (QFP) one in each of the two circuits, almost from the first wipe after setting up the screen in the printer one row had hardly had any paste on it. But it looked almost like “gray dandruff” on the pads. After about ten wipes it was exactly the same result seven groups of pads perfect, one group totally useless. As you can see from the picture.

So then I showed the foreman who immediately blamed solder paste saying that magic sentence “add some flux to the paste”

We (experienced SMT operators) all know you can not soften up the paste too much (not that a good operator would do that), otherwise the paste on the panel will look like “sand hills in the desert” after you lift the screen, when the paste on the panel should look like “skyscrapers in the city” on a miniature model of a city

As I have come from the electronics service trade found that the soldering on the leads of very hot parts deteriorated over time to the point where the joint break making the circuit intermittent. If one adds flux to paste that uses resin, this might speed up the process

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#69083

Is there any good articles to read on solder paste? | 28 May, 2013

Hi Eric,

your problem looks like a printing issue - if the part(or group of leads) missing solder is always the same. I would say you should check:

1. Stencil for any damage at this area 2. Squegee for damages 3. Adequate pin support un der the board 4. Printer parameters like pressure, speed, separation speed

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#69097

Is there any good articles to read on solder paste? | 29 May, 2013

OK the plot thickens: Yesterday used brand new paste, as it comes out, nothing added. Did about 13 panels, (or about 60 wipes) extra wipes because the PCB registration varies from panel panel. SAME PROBLEM ~ SAME PLACE.

Took all the paste off the screen, mixed it up, put it back on, back in business, still nothing added to it. Did another 5 panels took all the paste off cleaned and went home.

The blades we use to push the paste into the holes are all metal about as thick as meal knife, (no rubber included).

Yet when other screens are used with the same patten for the same IC there is never a problem apart from screen registration.

The answer: seems to be "that screen"

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#69098

Is there any good articles to read on solder paste? | 29 May, 2013

Hi Eric,

What type of printer are you using? I'm assuming its a manual print process.

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#69099

Is there any good articles to read on solder paste? | 29 May, 2013

I can not think of the name at the moment.

But is is a basic skeleton [table top model] type positively no computer driving it, or transistors for that matter.

Made in Switzerland, I will get the name and lengthen the thread.

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#69107

Is there any good articles to read on solder paste? | 30 May, 2013

I have another idea. Would you check the apertures on the stencil? May be they didn't cut the right size apertures there. If you have smaller aperture you can't get the right amount of paste.

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#69115

Is there any good articles to read on solder paste? | 30 May, 2013

I was more interested to read up on paste,

As for the short run of 50 panels was finished, the panels dribbled out slowly. about three times the second day I took off the paste, mixed it up and put it back on, seems to do the trick. Also I gave each panel two wipes. So some panels got about eight wipes (panel having been cleaned in between the two wipe cycle) if I was not happy, cleaning the screen each time cycle and blowing air through the screen holes of the IC.

As for the printer, the model is Cosey. (I think) Made by Contact systems LTD or Kontact systeme AG

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#69161

Is there any good articles to read on solder paste? | 4 June, 2013

So there is no articles on different solder paste then

By the way I have never seen one newsletter from SMTNET, apparently they end up in the spam folder and I am not looking in there otherwise I may as well have all my email going straight into the spam folder.

I did post the reason why all the newsletters go into the spam folder but someone deleted it

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#69162

Is there any good articles to read on solder paste? | 4 June, 2013

You can start with these!

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#69169

Is there any good articles to read on solder paste? | 5 June, 2013

Solders, Fluxes and Pastes - A Lab Report

This webcast consists of 10 individual program segments focused on the important topic of electronics solders, solder pastes and fluxes.

Program Segments Include: * Can You Mix Leaded and Lead-free? * Problem With No Clean Solder Flux Residue * Evaluation of Lead-free Solder Pastes * The Effects of Flux Residues on Reliability * The Digital Solder Paste * Pb-free Solder Joint Reliability * What is the Shelf Life of Solder Paste? * VOC Free Flux Study * Does Lead-free Flux Make a Difference?

Look here: http://www.ipcoutlook.org/webcasts/52685A.shtml

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#69535

Is there any good articles to read on solder paste? | 23 June, 2013

Sorry I have not been back here to thank you for your response, I have not been back since my last posting, (for about 20 days). As a SMT operator it is the most horrible job I have ever had in the 40 years in the workforce,

edit cut: I never got any reply from the extra information, however I thought it was superfluous to this forum and so not much point leaving it permanently.

From Eric

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