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Wave Solder Non wetting holes



Wave Solder Non wetting holes | 18 May, 2005

Hi, I am having some PTH non wetting issues. Setup and chronology of events is explained: Set Up; Part: 1 MM pitch connector 378 pins Solder: Kester Ultra Pure 63/37 solder Pot; 250 C pre heat; Peak 94C top side Flux: Qualitek 775, Fluxer: foam Thinner: Alcohol Sp gravity miantained: 0.85-0.9 Conveyor Speed: 1.1 m/min

Events issues: 1- A 0.003" int fit between a 0.020" hole and 0.018" square pin. 2-Non wetting of holes: The leads display good evidence of tinning/solder pick up. 3- Randomly some holes 25-30 per PCb will not wet while the leads are tinned. It appears as if the annular ring did not get enough flux/ flux got burnt off. However the adjacent will depict a perfect solder. 4-Second run of wave eliminates the non wetted holes. 4- Eliminating the preheat results in non wetting reducing to half.

Please advise what could be a cause for this wetting behaviour. I think that the PT holes are coming in contaminated to some extent which is the root cause of the failure. Could the flux/ preheat/ process setup be influencing the same?

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Wave Solder Non wetting holes | 18 May, 2005


Assuming that your dwell and coverage at the wave are in order.....

Have you checked the angle and pressure of your fluxer air knife? You can only count on capilary action to a point. The air knife, set correctly, will help get your flux to the top side of the board.

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Wave Solder Non wetting holes | 19 May, 2005

have you some GND layer inside the pcb ? see IPC 610 A

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Wave Solder Non wetting holes | 19 May, 2005

Hi Hoss, Thanks for your reply. Yes I am seeing the flux flood over to the top surface of my board, so to an extent I am not concerned with the fluxer. I believ that the foam fluxer is functioning adequately.

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Wave Solder Non wetting holes | 19 May, 2005

On the non-wetted holes put a solder iron to them and see if they "bubble" if so, you have some outgassing in your PCB and they will need to be baked prior to assembly. If this is okay I would investigate the grnd layer that was mentioned. What is your dwell time on the wave and are you using a dual wave setup? What type of flux is this qualitek?

Your second #4 is telling you something "no preheat = better" Sounds like flux is dying somewhere or the additional flux remaining is helping with the possible outgassing problem that you may have..

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Wave Solder Non wetting holes | 19 May, 2005

Hi all, There are no ground layers which makes the non wetting rate a bit confounding. The foam fluxer has not been cleaned in a while though, while there is a strong evidence of fluxing by running blank paper and looking up the top side of the boards after fluxing. I would not expect that selectively pins do not get fluxed. Just checked the bare fab for ionics and it showed 7.1 mg/sq in.

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Wave Solder Non wetting holes | 19 May, 2005

Is it possible your board is warping and skip plating? Have you run a lev-check? What does your contact patch look like?

Do you have ice cikles (spelling???) or solder "flags". IF yes, your flux is consumed or nonexistant. What is your dwell time (total chip + lambda)?

I have seen this on some really cheap machines (td) where the rails warp and become non linear forcing a variable contact patch. But, the glass plate reveals all....

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Wave Solder Non wetting holes | 20 May, 2005

We agree with Russ on item #4. "No preheat => better" doesn't make sense. Additionally with no preheat, primary side components see a large delta T when they hit the wave.

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