Wavesoldering Organic Copper Coated Vias

I have a single-sided board with test vias that pass through the board. The test vias are pasted and reflowed with the SMT components on the top side. When the boards are wavesoldered, the solder coverage on the vias is spotty. Some will solder, others will not. The coating is an organic copper coating (that's what we call it). We are using an aqueous flux. The major problem is our in-circuit tester will reject a board because the probes don't make good contact. Some other info: I sent a raw board through the wave and it soldered much better. (not 100%) The board layout is divided into two "sections" - one solders well, the other does not. (I'm not sure what's different) The vias in the different sections are "nested" differently. The vias on the good side are raised off the rest of the board, whereas the vias on the poor side seem to be in the same plane as the board surface around it. (There is a recessed square cut-out area where vias sit) We have a very similar board with a HASL coating with no reported problems. I have talked to others who say there is little that can be done to improve soldering bottom-side vias with the organic coating. Does anyone have more encouraging ideas? Thanks - Henry

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| I have a single-sided board with test vias that pass through the board. The test vias are pasted and reflowed with the SMT components on the top side. When the boards are wavesoldered, the solder coverage on the vias is spotty. Some will solder, others will not. The coating is an organic copper coating (that's what we call it). We are using an aqueous flux. | The major problem is our in-circuit tester will reject a board because the probes don't make good contact. | Some other info: | I sent a raw board through the wave and it soldered much better. (not 100%) | The board layout is divided into two "sections" - one solders well, the other does not. (I'm not sure what's different) | The vias in the different sections are "nested" differently. The vias on the good side are raised off the rest of the board, whereas the vias on the poor side seem to be in the same plane as the board surface around it. (There is a recessed square cut-out area where vias sit) | We have a very similar board with a HASL coating with no reported problems. | I have talked to others who say there is little that can be done to improve soldering bottom-side vias with the organic coating. | Does anyone have more encouraging ideas? | Thanks | - Henry

Henry, Could you be more definitive about "organic" copper? This is an interesting issue if it is what I think. We might all benefit if you could clarify - say from your board supplier just what the "coating" is. Earl Moon

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| | I have a single-sided board with test vias that pass through the board. The test vias are pasted and reflowed with the SMT components on the top side. When the boards are wavesoldered, the solder coverage on the vias is spotty. Some will solder, others will not. The coating is an organic copper coating (that's what we call it). We are using an aqueous flux. | | The major problem is our in-circuit tester will reject a board because the probes don't make good contact. | | Some other info: | | I sent a raw board through the wave and it soldered much better. (not 100%) | | The board layout is divided into two "sections" - one solders well, the other does not. (I'm not sure what's different) | | The vias in the different sections are "nested" differently. The vias on the good side are raised off the rest of the board, whereas the vias on the poor side seem to be in the same plane as the board surface around it. (There is a recessed square cut-out area where vias sit) | | We have a very similar board with a HASL coating with no reported problems. | | I have talked to others who say there is little that can be done to improve soldering bottom-side vias with the organic coating. | | Does anyone have more encouraging ideas? | | Thanks | | - Henry | | Henry, | Could you be more definitive about "organic" copper? | This is an interesting issue if it is what I think. | We might all benefit if you could clarify - say from | your board supplier just what the "coating" is. | Earl Moon

Earl, As I've added onto the title, by "Organic Copper" I mean the Entek Plus copper protective coating (or OSP). I found out the name right after posting my message. - Henry

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| I have a single-sided board with test vias that pass through the board. The test vias are pasted and reflowed with the SMT components on the top side. When the boards are wavesoldered, the solder coverage on the vias is spotty. Some will solder, others will not. The coating is an organic copper coating (that's what we call it). We are using an aqueous flux. | The major problem is our in-circuit tester will reject a board because the probes don't make good contact. | Some other info: | I sent a raw board through the wave and it soldered much better. (not 100%) | The board layout is divided into two "sections" - one solders well, the other does not. (I'm not sure what's different) | The vias in the different sections are "nested" differently. The vias on the good side are raised off the rest of the board, whereas the vias on the poor side seem to be in the same plane as the board surface around it. (There is a recessed square cut-out area where vias sit) | We have a very similar board with a HASL coating with no reported problems. | I have talked to others who say there is little that can be done to improve soldering bottom-side vias with the organic coating. | Does anyone have more encouraging ideas? | Thanks | - Henry Henry, Entek. Good stuff. Either you have too much or too little. If you have too much, your wave solder flux/preheat won't cut through it. If you have too little, it'll all burn off post-reflow and your pads will turn orange, pink, purple, and oil from the operators' hands will keep you from soldering. If you don't have enough, you better get that board over the wave soon after reflow. If you have too much, you need to attack it with flux and time at temperature to eat through it. I have a single-sided board with Entek that wasn't soldering well. Now I'm running a wave conveyor speed of 3.0 ft/minute (Soooooo slooooooo) and reaching a topside temp of 230F before I hit the wave. Soldering has vastly improved since the profile change (like from 5% to 75% yields, and all the fallout was open joints) Another helpful item - If you're printing on the wave solder side, print donuts (well donuts cut in thirds so the webs support the munchkin) on the annular rings. The flux in the solder paste is more active than the flux at the wave. Now your Entek pads will be pretinned and will take solder much easier. Chrys

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