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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Robert Wells

#11334

Need Wave Solder Help (SMT) | 26 May, 1999

we have just started wave soldering passive SMT components and through hole. We are having trouble with voids on the SMT components. It is very random, but effects a lot of TSOT's. We are using an electrovert with a chip wave. Are there any obvious things we need to check right up front?

thanks in advance, Robert Wells ACD Tridon

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JohnW

#11335

Re: Need Wave Solder Help (SMT) | 26 May, 1999

| we have just started wave soldering passive SMT components and through hole. We are having trouble with voids on the SMT components. It is very random, but effects a lot of TSOT's. We are using an electrovert with a chip wave. Are there any obvious things we need to check right up front? | | thanks in advance, | Robert Wells | ACD Tridon | Robert,

A couple of quick hit's that are worth checking.

Flux, not only that ur using the right one but that your using the right amount, too much is almost as bad as not enough. The application method cna be a factor, by far the best result's I've had is with spray fluxing, it's real controlable and you don't have to worry too much about the life of the flux like you do with foam. Check the flux to make sure that it's not died. Your preheat's are important, if your getting viod's you may have too much flux at the wave or it's too cold. Typically for a 6 layer board of mixed tech your looking at a top side temp of about 105 - 110 degrees C. The speed over the wave and the hieght of the chip wave can sometime's be a factor but generally void's = flux/preheat problem. But we need more info!!

JohnW

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Boca

#11336

Re: Need Wave Solder Help (SMT) | 26 May, 1999

| | we have just started wave soldering passive SMT components and through hole. We are having trouble with voids on the SMT components. It is very random, but effects a lot of TSOT's. We are using an electrovert with a chip wave. Are there any obvious things we need to check right up front? | | | | thanks in advance, | | Robert Wells | | ACD Tridon | | | Robert, | | A couple of quick hit's that are worth checking. | | Flux, not only that ur using the right one but that your using the right amount, too much is almost as bad as not enough. The application method cna be a factor, by far the best result's I've had is with spray fluxing, it's real controlable and you don't have to worry too much about the life of the flux like you do with foam. | Check the flux to make sure that it's not died. | Your preheat's are important, if your getting viod's you may have too much flux at the wave or it's too cold. Typically for a 6 layer board of mixed tech your looking at a top side temp of about 105 - 110 degrees C. | The speed over the wave and the hieght of the chip wave can sometime's be a factor but generally void's = flux/preheat problem. | But we need more info!! | | JohnW | A couple of more items to check;

1- What are the orientation of the SOT's to the conveyor? The SOT body should be parallel to the conveyor to prevent shadowing.

2- Is the chip nozzle cleaned out? We have to watch this very closely, the holes get plugged and we can begin to get consistant 'misses' in about the same area of the PCB.

Happy Soldering

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#11337

Re: Need Wave Solder Help (SMT) | 26 May, 1999

| | | we have just started wave soldering passive SMT components and through hole. We are having trouble with voids on the SMT components. It is very random, but effects a lot of TSOT's. We are using an electrovert with a chip wave. Are there any obvious things we need to check right up front? | | | | | | thanks in advance, | | | Robert Wells | | | ACD Tridon | | | | | Robert, | | | | A couple of quick hit's that are worth checking. | | | | Flux, not only that ur using the right one but that your using the right amount, too much is almost as bad as not enough. The application method cna be a factor, by far the best result's I've had is with spray fluxing, it's real controlable and you don't have to worry too much about the life of the flux like you do with foam. | | Check the flux to make sure that it's not died. | | Your preheat's are important, if your getting viod's you may have too much flux at the wave or it's too cold. Typically for a 6 layer board of mixed tech your looking at a top side temp of about 105 - 110 degrees C. | | The speed over the wave and the hieght of the chip wave can sometime's be a factor but generally void's = flux/preheat problem. | | But we need more info!! | | | | JohnW | | | A couple of more items to check; | | 1- What are the orientation of the SOT's to the conveyor? The SOT body should be parallel to the conveyor to prevent shadowing. | | 2- Is the chip nozzle cleaned out? We have to watch this very | closely, the holes get plugged and we can begin to get consistant 'misses' in about the same area of the PCB. | | Happy Soldering | Flux, heat, and solder. They are all equally important. Without any one of them, you don't get a joint.

First to rule out is heat. If the opens are random on the boards and the rest of the board is soldering well, it's porbably not an effect of bad preheat.

Flux and solder can be easily checked with an inexpensive and indispensable tool - a glass plate. Call the local glass store and ask for a piece of fireplace glass. The stuff is tempered to take the heat. Get it cut to accomodate whatever your typical conveyor width is. Should cost around 30 bucks, and worht every nickel. Run it through the fluxer to visually indicate even fluxing. Leave it on the conveyor and run it over the wave to check for contact. On an electrovert machine, you are looking for about 0.3 inches of contact on the chip wave and 1.5 on the smooth wave. At 5 ft/sec conveyor speed, that equals 0.3 seconds chip contact and 1.5 seconds wave contact.

Now, all that being said, as an "armchair quarteback" I'd tend to agree with Boca and say that most likely your chip nozzle is getting clogged, in which case you need to invest in a poker, or your packages are oriented wrong. If they are shadowing themselves, you'll need ot adjust your profile with more chip wave action to give them longer dwell in the chip.

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