Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Solder on gold finger

Masdi Muhammad

#14858

Solder on gold finger | 26 July, 1998

Hi, Need some advice on how to eliminate or reduce the solder on finger that we are having right now. So far what we understand is that 90% of the problem is due to the reflow process where solder traps in vias causing explosion when subjected to high temp during reflow. Not sure whether this is the right assumption but from what we have seen on the reject there are solder balls all over the 'exploded' vias. The signature of solder on finger defects is 10-40 mils of 'dot' which could be caused by solder balls. So this is my questions: 1. Is it possible that the vias can 'explode' during reflow? 2. Does the ramp from room temp to soaking time(145-160 deg C) and from soaking time (160-183 deg C) play an important role in determining the amount of 'explosion'. So far our data shows that it does. 3. Is there any other possible causes of solder explosion...Solder paste?

Thank you and really appreciate the help. Masdi Muhammad, Process Engineer.

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D.Lange

#14860

Re: Solder on gold finger | 27 July, 1998

| Hi, | Need some advice on how to eliminate or reduce the solder on finger that we are having right now. So far what we understand is that 90% of the problem is due to the reflow process where solder traps in vias causing explosion when subjected to high temp during reflow. Not sure whether this is the right assumption but from what we have seen on the reject there are solder balls all over the 'exploded' vias. The signature of solder on finger defects is 10-40 mils of 'dot' which could be caused by solder balls. So this is my questions: | 1. Is it possible that the vias can 'explode' during reflow? | 2. Does the ramp from room temp to soaking time(145-160 deg C) and from soaking time (160-183 deg C) play an important role in determining the amount of 'explosion'. So far our data shows that it does. | 3. Is there any other possible causes of solder explosion...Solder paste? | | Thank you and really appreciate the help. | Masdi Muhammad, | Process Engineer. Masdi, If you have access to an oven try baking them at about 105 deg. C. or 220 deg. F. for 8 or ten hrs. Put them in the oven overnite then process them in the morning. This problem seems to be unique with certain board manufacturers??? If touch up is required you are probably noticing solder popping as it is heated. A good baking will usually eliminate that. This can also be an annoying problem during wave soldering. Good luck!

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Bob Willis

#14861

Re: Solder on gold finger | 28 July, 1998

The causes for solder on gold are: Paste wash offs Dirty stencils Dirty under stencil cleaning cloths/no solvent Poor handling The most common reason is wash offs when there is a couple of balls left on the tabs and they reflow. With correct profile the paste does not explode. Vias can not gas if the board is produced correctly. There is a section on FAQs on my web site covering solder balls www.bobwillis.co.uk | | Hi, | | Need some advice on how to eliminate or reduce the solder on finger that we are having right now. So far what we understand is that 90% of the problem is due to the reflow process where solder traps in vias causing explosion when subjected to high temp during reflow. Not sure whether this is the right assumption but from what we have seen on the reject there are solder balls all over the 'exploded' vias. The signature of solder on finger defects is 10-40 mils of 'dot' which could be caused by solder balls. So this is my questions: | | 1. Is it possible that the vias can 'explode' during reflow? | | 2. Does the ramp from room temp to soaking time(145-160 deg C) and from soaking time (160-183 deg C) play an important role in determining the amount of 'explosion'. So far our data shows that it does. | | 3. Is there any other possible causes of solder explosion...Solder paste? | | | | Thank you and really appreciate the help. | | Masdi Muhammad, | | Process Engineer. | Masdi, | If you have access to an oven try baking them at about 105 deg. C. or 220 deg. F. for 8 or ten hrs. Put them in the oven overnite then process them in the morning. This problem seems to be unique with certain board manufacturers??? | If touch up is required you are probably noticing solder popping as it is heated. A good baking will usually eliminate that. This can also be an annoying problem during wave soldering. Good luck!

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zambri

#14859

Re: Solder on gold finger | 18 August, 1998

| Hi, | Need some advice on how to eliminate or reduce the solder on finger that we are having right now. So far what we understand is that 90% of the problem is due to the reflow process where solder traps in vias causing explosion when subjected to high temp during reflow. Not sure whether this is the right assumption but from what we have seen on the reject there are solder balls all over the 'exploded' vias. The signature of solder on finger defects is 10-40 mils of 'dot' which could be caused by solder balls. So this is my questions: | 1. Is it possible that the vias can 'explode' during reflow? | 2. Does the ramp from room temp to soaking time(145-160 deg C) and from soaking time (160-183 deg C) play an important role in determining the amount of 'explosion'. So far our data shows that it does. | 3. Is there any other possible causes of solder explosion...Solder paste? | | Thank you and really appreciate the help. | Masdi Muhammad, | Process Engineer.

Masdi, There's a new technology/advance paste in the market which is Epoxy base. Work with your local paste manufacturer and give it a try. cheers.. zambri

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