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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Grainy soler

Victor Salazar

#22278

Grainy soler | 5 November, 2002

I am seeing quite a bit of grainy solder joints. I am told this can be from being in a liquidus state for too long. Does anybody have any information on this defect?

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#22279

Grainy soler | 5 November, 2002

Grainy solder is a process indicator. It is not necessarily a defect. Search fine SMTnet Archives for background.

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cvrgirl

#22298

Grainy soler | 6 November, 2002

Hi Victor, I made many micro-sections for analysis, and I have seen porous, dense, and grainy solder joints. The condition has to do with the constituents within the solder and its reflow temperature. I can search your subject on IEEE and email you relative articles, if you still need more information. Um...can you download me an article in SMTA-Int'l? Email me offline if you want to share knowledge. Michelle

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Victor salazar

#22374

Grainy soler | 11 November, 2002

Michelle, I am very interested in hearing your results. Do you have any pics of grainy solder? You may e-mail me direct with any info. I would appreciate it. Thankyou vsalazar@uasc.com

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steve

#22382

Grainy soler | 12 November, 2002

Your heating temperature is too low. Check your process and run the board through again. Then the graininess problem should go away. Or, try some different solder.

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ruimsig

#22465

Grainy soler | 21 November, 2002

The cause of grainy joints is either too high reflow max 225�C, 90 seconds or the reflow temp was tp low

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Kevin Facinelli

#22479

Grainy soler | 22 November, 2002

I would have to agree with the to high temp being a real problem. I have seen this with the WS-609 alpha paste. If you run it up to high in temp. The joints appear to be cold but they are really just over fried.....definitely try reducing temperature before switching pastes.

Kevin

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#22480

Grainy soler | 22 November, 2002

This condition could also be caused by gold plated pads.

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robertorre

#22491

Grainy soler | 22 November, 2002

Your problem may be related to different aspects. 1. Oxidation on landing pads. 2. Either high(To long over liquidous temp) or low temp. 3. Bad solder (not enough vehicles) Run this test: Set a hot plate to 220 degrees C. Make sure you have proper ventilation. Print solder paste. Populate components. Using pliers or tweezers hold the board close to the surface of the hot plate to start getting it hot. Slowly place the board on the hot plate and observe how is the reflow. Wear a mask and safety glasses. After liquidous state is observed keep the range of time between 30 to sixty seconds. If succesful reflow is obtained, there in no oxidation, there is no bad solder and your reflow process need some work. If you have a reflow profiler you may want to attach thermocouples to the components (different components ) and compare the results. Ask your solder supplier for a recomended profile. Let me know

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