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Sticky solder, solder flagging, bridging.

Sticky solder, solder flagging, bridging.

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Hello All, We have a small selective solder machine from RPS... - Apr 19, 2023 by James V

What Purity is the N2? ... - Apr 20, 2023 by ProcEng1

5 ppm from cylinders, thank you for taking the time to respo... - Apr 20, 2023 by James V

images? length of leads sticking out of pcb? pitch? ... - Apr 21, 2023 by bukas

I mean...there are a ton of possibilities for bridging on se... - Apr 21, 2023 by robgd3

I had also increased my flux to see if that helped, it did n... - Apr 21, 2023 by James V

Hi Rob, Yes I agree with everything stated. Lots of things c... - Apr 21, 2023 by James V

What kind of fume extraction are you using? If its too high,... - Apr 21, 2023 by DWL

It is pretty high, I will have to try it with no exhaust, th... - Apr 21, 2023 by James V

looks like low nitrogen to me ... - Apr 24, 2023 by bukas

Hi Bukas, thank you for taking the time to respond. My flow ... - May 02, 2023 by James V

I made a nitrogen nozzle from a starfrite silicone funnel an... - May 02, 2023 by James V

It was a nitrogen delivery issue. I used a funnel (silicone)... - Jun 12, 2023 by James V

James V

#89224

Sticky solder, solder flagging, bridging. | 19 April, 2023

Hello All, We have a small selective solder machine from RPS, a Rhythm SS, purchased used with SN100C in pot. For a couple of years we have used this machine and gotten good results. We have been adding SN995 to the pot as it needed more solder. Then we started getting bridging and flagging. Not saying its related to the SN995. Our pot temperature is 300C. No matter what speed we run at, or wave height, it has bridges and flagging. We run the flux that the SN995 manufacturer recommends, the nitrogen pre heat 150C. Our solder analysis showed high Nickel content. Ni 0.063 0.0500 Fail, do you think that the Nickle is source of our bridging issue?

Any suggestions would be welcome, the amount of rework is over the top with this issue.

Thank you and have a great day everyone.

Element Result

Ag 0.013 4.0000 Pass Al 0.0005 0.0060 Pass As 0.0012 0.0300 Pass Au ~ 0.013 0.2000 Pass Bi 0.0036 0.2500 Pass Cd < 0.0001 0.0050 Pass Cu 0.782 1.1000 Pass Fe 0.0043 0.0200 Pass In 0.00067 Ni 0.063 0.0500 Fail Pb 0.023 0.1000 Pass Sb 0.01 0.2000 Pass Sn 99.08 +/- 1% Pass Zn 0.00029 0.0050 Pass

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ProcEng1

#89229

Sticky solder, solder flagging, bridging. | 20 April, 2023

What Purity is the N2?

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James V

#89231

Sticky solder, solder flagging, bridging. | 20 April, 2023

5 ppm from cylinders, thank you for taking the time to respond. Originally I ran no spec nitrogen, and got good results, when I started having issues I changed to 4.8 spec

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bukas

#89235

Sticky solder, solder flagging, bridging. | 21 April, 2023

images? length of leads sticking out of pcb? pitch?

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robgd3

#89241

Sticky solder, solder flagging, bridging. | 21 April, 2023

I mean...there are a ton of possibilities for bridging on selective solder before you ever get to alloy purity.

Are the bridges happening consistently in the same spot? Are the leads too long? Can you modify the approach/exit/peel off to address? What is the pitch of the leads that are bridging? Are the bridges across areas of common temperature load? Are there any temperature load mis-balances between the shorts? Are you experiencing any new amounts of dross? Are you cleaning the dross from the pot? Is the nozzle a good size for the area you're trying to solder? Is the nozzle well tinned? Is the height of the wave too high/too low? Are you pre-heating the board? Have you confirmed flux coverage in this area? Confirmed N2 coverage over the nozzle?

I'm not going to say that alloy purity isn't contributing to your issues, but, it would be very low on my list of things to look at.

cheers, ..rob

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James V

#89242

Sticky solder, solder flagging, bridging. | 21 April, 2023

I had also increased my flux to see if that helped, it did not. 2mm lead length, 5.08 spacing Thank you

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James V

#89243

Sticky solder, solder flagging, bridging. | 21 April, 2023

Hi Rob, Yes I agree with everything stated. Lots of things can cause this. I have gone over everything mentioned in your response. The thing is, I could do a simple drag and had no issues, then a few bridges then more. So I have checked everything, machine level, good flow on the nozzle, about a 5mm wave height, N2. What I was trying to find out is, is it possible that a nickel higher nickel content could cause bridging issues? It failed the solder analysis, but is it a problem? Thank you for taking the time to respond.

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DWL

#89244

Sticky solder, solder flagging, bridging. | 21 April, 2023

What kind of fume extraction are you using? If its too high, you could be pulling the nitrogen off of the nozzle.

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James V

#89245

Sticky solder, solder flagging, bridging. | 21 April, 2023

It is pretty high, I will have to try it with no exhaust, thanks for the idea. Have a great weekend. I should also mention someone that knows metal alloys told me that that much extra Nickle can cause the melt point to go up. Does anyone run hotter then 300C? I am not sure if the alloy could be "damaged" from high heat.

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bukas

#89251

Sticky solder, solder flagging, bridging. | 24 April, 2023

looks like low nitrogen to me

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James V

#89282

Sticky solder, solder flagging, bridging. | 2 May, 2023

Hi Bukas, thank you for taking the time to respond. My flow gauge shows 35 SCFH and the pressure is around 50 psi. Maybe the flow gauge is wrong? Thanks again. What delivery pressure do you run, if you run a selective solder machine? Thanks again. I use cylinders, one cylinder lasts around 3 hours.

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James V

#89283

Sticky solder, solder flagging, bridging. | 2 May, 2023

I made a nitrogen nozzle from a starfrite silicone funnel and it improved the issue by about 80%. Thanks for the feedback

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James V

#89551

Sticky solder, solder flagging, bridging. | 12 June, 2023

It was a nitrogen delivery issue. I used a funnel (silicone) to direct the nitrogen to the board. The way the machine operates is, the nitrogen comes out about 7 cm away from the board, from a large opening around the nozzle. I cut a silicone funnel to fit over the nozzle and nitrogen shroud. This directs the nitrogen to the PCB. This solved me problem. So I think the baffle in the RPS machine which is used to disperse the nitrogen around the print head, possibly has issues. I still need to pull it and check its flow. I suspect it has flow issues on one part of it. The silicone funnel let me drop my delivery pressure and still get good results. I know get around 6 hours from 1 bottle, compared to under 3 before. I am also not sure but I changed the solder used in the machine from SN100C to SN995, others have no issue with this so maybe it is not related. SN100C is specially designed for Selective Solder and the germanium helps reduce bridging. I am still using SN995.

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