Wave solder edge covers

We are wave soldering some fabs with a lot of unmasked trace area along the edges. The trace area is solid copper covered with tin / lead, no masking, no components along the edges, same on solder side and component side (goofy board design). Instead of using the typical polyimide tape along both edges I am trying some fiberglass edge covers, the cover material is 0.032 thick (they are often used to cover gold fingers). Flux is OA, equipment is name brand with 2 stages of bottom side preheat, and a thermal profile matching the fluxing requirements.

My problem; After soldering, the tin lead surface under the edge cover appears tarnished on solder side and component side. The tarnish will not wash off. Since most of the component side is solid tin/lead, and unmasked, this is really obvious. The customer will consider this an unacceptable cosmetic defect.

It may be a function of the flux wicking under the cover. Or the tin lead is reflowing under the edge covers, but I can't believe it's reflowing under the covers on the component side.

Any suggestions to the mechinism at work here? Has anyone made fiberglass covers work in this kind of application? I'd like to hear your experiences related to this.

Thanks

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| We are wave soldering some fabs with a lot of unmasked trace area along the edges. The trace area is solid copper covered with tin / lead, no masking, no components along the edges, same on solder side and component side (goofy board design). Instead of using the typical polyimide tape along both edges I am trying some fiberglass edge covers, the cover material is 0.032 thick (they are often used to cover gold fingers). Flux is OA, equipment is name brand with 2 stages of bottom side preheat, and a thermal profile matching the fluxing requirements. | | My problem; After soldering, the tin lead surface under the edge cover appears tarnished on solder side and component side. The tarnish will not wash off. Since most of the component side is solid tin/lead, and unmasked, this is really obvious. The customer will consider this an unacceptable cosmetic defect. | | It may be a function of the flux wicking under the cover. Or the tin lead is reflowing under the edge covers, but I can't believe it's reflowing under the covers on the component side. | | Any suggestions to the mechinism at work here? Has anyone made fiberglass covers work in this kind of application? I'd like to hear your experiences related to this. | | Thanks | It almost sounds like the same issue that I had not too long ago - with one slight twist. My issue involved a nickel covered copper. Tinlead was then applied to the nickel. The problem was that there was too much nickel plating. When the area would heat up, the nickel would turn dark/black and would make the tin/lead look as though it was tarnished. Once the vendor reduced the amount of nickel plating, the problem went away.

The area was also isolated from direct contact with the solder bath also.

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| | We are wave soldering some fabs with a lot of unmasked trace area along the edges. The trace area is solid copper covered with tin / lead, no masking, no components along the edges, same on solder side and component side (goofy board design). Instead of using the typical polyimide tape along both edges I am trying some fiberglass edge covers, the cover material is 0.032 thick (they are often used to cover gold fingers). Flux is OA, equipment is name brand with 2 stages of bottom side preheat, and a thermal profile matching the fluxing requirements. | | | | My problem; After soldering, the tin lead surface under the edge cover appears tarnished on solder side and component side. The tarnish will not wash off. Since most of the component side is solid tin/lead, and unmasked, this is really obvious. The customer will consider this an unacceptable cosmetic defect. | | | | It may be a function of the flux wicking under the cover. Or the tin lead is reflowing under the edge covers, but I can't believe it's reflowing under the covers on the component side. | | | | Any suggestions to the mechinism at work here? Has anyone made fiberglass covers work in this kind of application? I'd like to hear your experiences related to this. | | | | Thanks | | | It almost sounds like the same issue that I had not too long ago - with one slight twist. My issue involved a nickel covered copper. Tinlead was then applied to the nickel. The problem was that there was too much nickel plating. When the area would heat up, the nickel would turn dark/black and would make the tin/lead look as though it was tarnished. Once the vendor reduced the amount of nickel plating, the problem went away. | | The area was also isolated from direct contact with the solder bath also. | My guess would be trapped flux continuing to be active after soldering. Is the tarnish there immediately after exiting the machine? Do you remove the mask and wash right away? If the solder is reflowing under the mask on the component side it would also all over the board so that's not likely. Try the Kapton tape to eliminate the possibility of the flux being the problem and see what happens. There are cheaper tapes that will survive. I use the Stevens (?) finger covers every day but only on gold and with no clean. Could there be some sort of contamination inside the covers? Speaking of contamination, I'd be carefull about using those covers on gold fingers after being over solder. good luck - John Thorup

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| My guess would be trapped flux continuing to be active after soldering. Is the tarnish there immediately after exiting the machine? Do you remove the mask and wash right away? If the solder is reflowing under the mask on the component side it would also all over the board so that's not likely. Try the Kapton tape to eliminate the possibility of the flux being the problem and see what happens. There are cheaper tapes that will survive. I use the Stevens (?) finger covers every day but only on gold and with no clean. Could there be some sort of contamination inside the covers? Speaking of contamination, I'd be carefull about using those covers on gold fingers after being over solder. | good luck - John Thorup | We remove the edge covers immediately after soldering, the tarnishing is present right away. I know Kapton tape works, that what I am trying to replace. You're right about it being a Steven's product, they do work fine on gold. We did try washing the covers in a saponified wash, with no change in results.

Thanks for your thoughtful responses!

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| | | My guess would be trapped flux continuing to be active after soldering. Is the tarnish there immediately after exiting the machine? Do you remove the mask and wash right away? If the solder is reflowing under the mask on the component side it would also all over the board so that's not likely. Try the Kapton tape to eliminate the possibility of the flux being the problem and see what happens. There are cheaper tapes that will survive. I use the Stevens (?) finger covers every day but only on gold and with no clean. Could there be some sort of contamination inside the covers? Speaking of contamination, I'd be carefull about using those covers on gold fingers after being over solder. | | good luck - John Thorup | | | We remove the edge covers immediately after soldering, the tarnishing is present right away. I know Kapton tape works, that what I am trying to replace. You're right about it being a Steven's product, they do work fine on gold. We did try washing the covers in a saponified wash, with no change in results. | | Thanks for your thoughtful responses! | | | Have you tried using "PETERS" peelable solder mask. This has worked for me in the past. I usually recomend prospect customers this matterial durring a DFM report. This peelable solder mask is placed at the board house, it does increase the cost of your board but it eliminates the masking, tapping and adding stiffners.

thanks

Tony A

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| | | We are wave soldering some fabs with a lot of unmasked trace area along the edges. The trace area is solid copper covered with tin / lead, no masking, no components along the edges, same on solder side and component side (goofy board design). Instead of using the typical polyimide tape along both edges I am trying some fiberglass edge covers, the cover material is 0.032 thick (they are often used to cover gold fingers). Flux is OA, equipment is name brand with 2 stages of bottom side preheat, and a thermal profile matching the fluxing requirements. | | | | | | My problem; After soldering, the tin lead surface under the edge cover appears tarnished on solder side and component side. The tarnish will not wash off. Since most of the component side is solid tin/lead, and unmasked, this is really obvious. The customer will consider this an unacceptable cosmetic defect. | | | | | | It may be a function of the flux wicking under the cover. Or the tin lead is reflowing under the edge covers, but I can't believe it's reflowing under the covers on the component side. | | | | | | Any suggestions to the mechinism at work here? Has anyone made fiberglass covers work in this kind of application? I'd like to hear your experiences related to this. | | | | | | Thanks | | | | | It almost sounds like the same issue that I had not too long ago - with one slight twist. My issue involved a nickel covered copper. Tinlead was then applied to the nickel. The problem was that there was too much nickel plating. When the area would heat up, the nickel would turn dark/black and would make the tin/lead look as though it was tarnished. Once the vendor reduced the amount of nickel plating, the problem went away. | | | | The area was also isolated from direct contact with the solder bath also. | | | My guess would be trapped flux continuing to be active after soldering. Is the tarnish there immediately after exiting the machine? Do you remove the mask and wash right away? If the solder is reflowing under the mask on the component side it would also all over the board so that's not likely. Try the Kapton tape to eliminate the possibility of the flux being the problem and see what happens. There are cheaper tapes that will survive. I use the Stevens (?) finger covers every day but only on gold and with no clean. Could there be some sort of contamination inside the covers? Speaking of contamination, I'd be carefull about using those covers on gold fingers after being over solder. | good luck - John Thorup | | Dear John,

Can you elaborate on the Stevens Finger covers !!... Please provide more details/source for getting the same.

Thanks Vinesh Gandhi

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| | | | We are wave soldering some fabs with a lot of unmasked trace area along the edges. The trace area is solid copper covered with tin / lead, no masking, no components along the edges, same on solder side and component side (goofy board design). Instead of using the typical polyimide tape along both edges I am trying some fiberglass edge covers, the cover material is 0.032 thick (they are often used to cover gold fingers). Flux is OA, equipment is name brand with 2 stages of bottom side preheat, and a thermal profile matching the fluxing requirements. | | | | | | | | My problem; After soldering, the tin lead surface under the edge cover appears tarnished on solder side and component side. The tarnish will not wash off. Since most of the component side is solid tin/lead, and unmasked, this is really obvious. The customer will consider this an unacceptable cosmetic defect. | | | | | | | | It may be a function of the flux wicking under the cover. Or the tin lead is reflowing under the edge covers, but I can't believe it's reflowing under the covers on the component side. | | | | | | | | Any suggestions to the mechinism at work here? Has anyone made fiberglass covers work in this kind of application? I'd like to hear your experiences related to this. | | | | | | | | Thanks | | | | | | | It almost sounds like the same issue that I had not too long ago - with one slight twist. My issue involved a nickel covered copper. Tinlead was then applied to the nickel. The problem was that there was too much nickel plating. When the area would heat up, the nickel would turn dark/black and would make the tin/lead look as though it was tarnished. Once the vendor reduced the amount of nickel plating, the problem went away. | | | | | | The area was also isolated from direct contact with the solder bath also. | | | | | My guess would be trapped flux continuing to be active after soldering. Is the tarnish there immediately after exiting the machine? Do you remove the mask and wash right away? If the solder is reflowing under the mask on the component side it would also all over the board so that's not likely. Try the Kapton tape to eliminate the possibility of the flux being the problem and see what happens. There are cheaper tapes that will survive. I use the Stevens (?) finger covers every day but only on gold and with no clean. Could there be some sort of contamination inside the covers? Speaking of contamination, I'd be carefull about using those covers on gold fingers after being over solder. | | good luck - John Thorup | | | | | Dear John, | | Can you elaborate on the Stevens Finger covers !!... Please provide more details/source for getting the same. | | Thanks | Vinesh Gandhi | | These are a pultruded fibreglass product made in a number of shapes. The "Gold Finger Gloves" are a slip on U shape intended to be a temporary mask for gold fingers. I like them because they are quick, easy, work well and are not a consumable. They also make and H shape that they promote for panel creation, a Y shape useful for creating a breakaway when your thoughtful designer didn't think about the connectors hanging over the edge of the board and traditional board stiffeners. Stevens Products 128 N Park St. East Orange N.J. 07017 973/672-2140 973/672-2837 fax

John Thorup

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| | | | We are wave soldering some fabs with a lot of unmasked trace area along the edges. The trace area is solid copper covered with tin / lead, no masking, no components along the edges, same on solder side and component side (goofy board design). Instead of using the typical polyimide tape along both edges I am trying some fiberglass edge covers, the cover material is 0.032 thick (they are often used to cover gold fingers). Flux is OA, equipment is name brand with 2 stages of bottom side preheat, and a thermal profile matching the fluxing requirements. | | | | | | | | My problem; After soldering, the tin lead surface under the edge cover appears tarnished on solder side and component side. The tarnish will not wash off. Since most of the component side is solid tin/lead, and unmasked, this is really obvious. The customer will consider this an unacceptable cosmetic defect. | | | | | | | | It may be a function of the flux wicking under the cover. Or the tin lead is reflowing under the edge covers, but I can't believe it's reflowing under the covers on the component side. | | | | | | | | Any suggestions to the mechinism at work here? Has anyone made fiberglass covers work in this kind of application? I'd like to hear your experiences related to this. | | | | | | | | Thanks | | | | | | | It almost sounds like the same issue that I had not too long ago - with one slight twist. My issue involved a nickel covered copper. Tinlead was then applied to the nickel. The problem was that there was too much nickel plating. When the area would heat up, the nickel would turn dark/black and would make the tin/lead look as though it was tarnished. Once the vendor reduced the amount of nickel plating, the problem went away. | | | | | | The area was also isolated from direct contact with the solder bath also. | | | | | My guess would be trapped flux continuing to be active after soldering. Is the tarnish there immediately after exiting the machine? Do you remove the mask and wash right away? If the solder is reflowing under the mask on the component side it would also all over the board so that's not likely. Try the Kapton tape to eliminate the possibility of the flux being the problem and see what happens. There are cheaper tapes that will survive. I use the Stevens (?) finger covers every day but only on gold and with no clean. Could there be some sort of contamination inside the covers? Speaking of contamination, I'd be carefull about using those covers on gold fingers after being over solder. | | good luck - John Thorup | | | | | Dear John, | | Can you elaborate on the Stevens Finger covers !!... Please provide more details/source for getting the same. | | Thanks | Vinesh Gandhi | | These are a pultruded fibreglass product produced in a number of shapes. The "Gold Fingers Gloves" are a U channel designed to be slipped over contact fingers as a temporary solder mask. I like them because they are quick, easy, reliable and are not a consumable. They make and H shape for panelizing boards, traditional stiffeners, and a Y shape that will function as a breakaway to use when your thoughtful designer forgets about the connectors hanging over the edge of your board. Stevens Products 973/672-2140 973/672-2837 fax

John Thorup

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