Warpage at Wave Soldering Stage

We are a medium sized PCB assy. house manufacturing about 2000 motherboards a day. There is a major problem we are facing at the wave soldering stage, i.e. warpage of the PCB. As soon as the PCB touches the wave it warps severely from the centre to the extent that the bottom side pins touch the solder pot leading to pin on height problem/insufficient solder problem on the corner components.

The solder bath temp. is 240 degree C and the profile as such seems to be O.k. The PCB thickness is 1.6 mm.

O!!... Wave Soldering GURUS of the world, please help me finding the possible causes for this problem and suggest corrective actions for the same. I will be obliged.

Best Regards Vinesh Gandhi

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| We are a medium sized PCB assy. house manufacturing about 2000 motherboards a day. There is a major problem we are facing at the wave soldering stage, i.e. warpage of the PCB. As soon as the PCB touches the wave it warps severely from the centre to the extent that the bottom side pins touch the solder pot leading to pin on height problem/insufficient solder problem on the corner components. | | The solder bath temp. is 240 degree C and the profile as such seems to be O.k. The PCB thickness is 1.6 mm. | | O!!... Wave Soldering GURUS of the world, please help me finding the possible causes for this problem and suggest corrective actions for the same. I will be obliged. | | Best Regards | Vinesh Gandhi |

Well, if you say your profile is okay, then that means that you're probably not heating your board and parts up too fast. Some of the main causes of warping are uneven thermal distribution and/or massive, heavy components that suck up heat or cause the boards to sag. Have you tried probing and profiling different areas of the board during the process? Also, are you using titanium stiffeners?

C.K.

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| We are a medium sized PCB assy. house manufacturing about 2000 motherboards a day. There is a major problem we are facing at the wave soldering stage, i.e. warpage of the PCB. As soon as the PCB touches the wave it warps severely from the centre to the extent that the bottom side pins touch the solder pot leading to pin on height problem/insufficient solder problem on the corner components. | | The solder bath temp. is 240 degree C and the profile as such seems to be O.k. The PCB thickness is 1.6 mm. | | O!!... Wave Soldering GURUS of the world, please help me finding the possible causes for this problem and suggest corrective actions for the same. I will be obliged. | | Best Regards | Vinesh Gandhi | You're sure having fun in a not too fun world of the big mutha board. One warpage problem is MLB constructions (not homogeneous or unbalanced - too resin rich or poor), poor supplier process capabilities (lamination cycles), poor material selections (usually cheap and dirty), etc. That's more than one? There are more not necessarily related to wave or any other type soldering operations.

Earl Moon

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| We are a medium sized PCB assy. house manufacturing about 2000 motherboards a day. There is a major problem we are facing at the wave soldering stage, i.e. warpage of the PCB. As soon as the PCB touches the wave it warps severely from the centre to the extent that the bottom side pins touch the solder pot leading to pin on height problem/insufficient solder problem on the corner components. | | The solder bath temp. is 240 degree C and the profile as such seems to be O.k. The PCB thickness is 1.6 mm. | | O!!... Wave Soldering GURUS of the world, please help me finding the possible causes for this problem and suggest corrective actions for the same. I will be obliged. | | Best Regards | Vinesh Gandhi |

I've had similar problems in the past, and most of them can be traced back to board consturction. Not much help when you've got a bunch of these puppies in stock, eh? A few things you can try:

1) Reprofile - go slower on your belt speed. I know this sounds counterintuitive, but it works because you get better themral distribution.

2) Get a pallet made. Nothin' fancy, just a frame, BUT (here's the trcky part) clamp the board all the way up ech side of the pallet. Not just single point hold-downs, but a bar that holds it all the way up. You see, for a board to warp down in the middle, it has to warp up on the edges. If it cant bend up easily, it will not bend down as easily, either. It takes a lot more stress to creat a point of inflection in the curvature than it does to make a dish. You can get these kind of pallets from EMC Global ( I think they have a link from this net now.) Tell them you want the entire edge held. They can make these; they did it for me.

Chrys

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| We are a medium sized PCB assy. house manufacturing about 2000 motherboards a day. There is a major problem we are facing at the wave soldering stage, i.e. warpage of the PCB. As soon as the PCB touches the wave it warps severely from the centre to the extent that the bottom side pins touch the solder pot leading to pin on height problem/insufficient solder problem on the corner components. | | The solder bath temp. is 240 degree C and the profile as such seems to be O.k. The PCB thickness is 1.6 mm. | | O!!... Wave Soldering GURUS of the world, please help me finding the possible causes for this problem and suggest corrective actions for the same. I will be obliged. | | Best Regards | Vinesh Gandhi | Vinesh,

I'm with Chrys and Earl, sound's like bad boards or posible badly designed ones with big heatsink's and lot n lot's of copper. If it's the big heatsink area's then it's back to the design board and heat modeling, cross hatch and spread the heat about abit. If that's OK then kill the board supplier! perhaps a quick check is run an empty board over the wave without any big heat sinking components that way you eliminate them from the equation

JohnW

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| | We are a medium sized PCB assy. house manufacturing about 2000 motherboards a day. There is a major problem we are facing at the wave soldering stage, i.e. warpage of the PCB. As soon as the PCB touches the wave it warps severely from the centre to the extent that the bottom side pins touch the solder pot leading to pin on height problem/insufficient solder problem on the corner components. | | | | The solder bath temp. is 240 degree C and the profile as such seems to be O.k. The PCB thickness is 1.6 mm. | | | | O!!... Wave Soldering GURUS of the world, please help me finding the possible causes for this problem and suggest corrective actions for the same. I will be obliged. | | | | Best Regards | | Vinesh Gandhi | | | | I've had similar problems in the past, and most of them can be traced back to board consturction. Not much help when you've got a bunch of these puppies in stock, eh? A few things you can try: | | 1) Reprofile - go slower on your belt speed. I know this sounds counterintuitive, but it works because you get better themral distribution. | | 2) Get a pallet made. Nothin' fancy, just a frame, BUT (here's the trcky part) clamp the board all the way up ech side of the pallet. Not just single point hold-downs, but a bar that holds it all the way up. You see, for a board to warp down in the middle, it has to warp up on the edges. If it cant bend up easily, it will not bend down as easily, either. It takes a lot more stress to creat a point of inflection in the curvature than it does to make a dish. You can get these kind of pallets from EMC Global ( I think they have a link from this net now.) Tell them you want the entire edge held. They can make these; they did it for me. | | Chrys |

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| We are a medium sized PCB assy. house manufacturing about 2000 motherboards a day. There is a major problem we are facing at the wave soldering stage, i.e. warpage of the PCB. As soon as the PCB touches the wave it warps severely from the centre to the extent that the bottom side pins touch the solder pot leading to pin on height problem/insufficient solder problem on the corner components. | | The solder bath temp. is 240 degree C and the profile as such seems to be O.k. The PCB thickness is 1.6 mm.

| | O!!... Wave Soldering GURUS of the world, please help me finding the possible causes for this problem and suggest corrective actions for the same. I will be obliged. | | Best Regards | Vinesh Gandhi | You didn't mention the size of the PCB. The problem could very well be with your fabricator. Do you measure the warp and twist on the bds during an incoming inspection? You might want to take a look to determine if the bds are good from the start. I have used boards stiffners on problem bds. (The pallet is also a good idea). You can design a stiffner that attaches from front to back with spring-loaded standoffs to hold it straight, or you could attach with screws if there are available holes. Bd size would determine how many stiffners you need. Its mostly trial and error on these types of problems.

Good Luck! Arthur

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| | We are a medium sized PCB assy. house manufacturing about 2000 motherboards a day. There is a major problem we are facing at the wave soldering stage, i.e. warpage of the PCB. As soon as the PCB touches the wave it warps severely from the centre to the extent that the bottom side pins touch the solder pot leading to pin on height problem/insufficient solder problem on the corner components. | | | | The solder bath temp. is 240 degree C and the profile as such seems to be O.k. The PCB thickness is 1.6 mm. | | | | O!!... Wave Soldering GURUS of the world, please help me finding the possible causes for this problem and suggest corrective actions for the same. I will be obliged. | | | | Best Regards | | Vinesh Gandhi | | | | | Well, if you say your profile is okay, then that means that you're probably not heating your board and parts up too fast. Some of the main causes of warping are uneven thermal distribution and/or massive, heavy components that suck up heat or cause the boards to sag. Have you tried probing and profiling different areas of the board during the process? Also, are you using titanium stiffeners? | | C.K. | An alternative to stiffeners or pallets, which increase process and labor time, is to use the center wire support on your wave machine if it has one. We used to use that on our electrovert, and it worked well. We also used front and leading edge stiffeners for boards that the center wire could not be used on.

Brian

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| We are a medium sized PCB assy. house manufacturing about 2000 motherboards a day. There is a major problem we are facing at the wave soldering stage, i.e. warpage of the PCB. As soon as the PCB touches the wave it warps severely from the centre to the extent that the bottom side pins touch the solder pot leading to pin on height problem/insufficient solder problem on the corner components. | | The solder bath temp. is 240 degree C and the profile as such seems to be O.k. The PCB thickness is 1.6 mm. | | O!!... Wave Soldering GURUS of the world, please help me finding the possible causes for this problem and suggest corrective actions for the same. I will be obliged. | | Best Regards | Vinesh Gandhi |

Vinesh, There are a couple of factors that need to be considered. (I assume that you are using 63/37 lead tin in your pot, and we run it at 490'F (250'C) and we can still run well.) The most important thing on warpage is the difference in temperature between the top and the bottom of the PCB. The closer the temperatures are together the more uniform expantion you will have, resulting is less worpage. Having said that you have to consider the activation and working temperature of your flux and your components. We use a preheat temp max of 190'F-220'F. We also use a device several wave hardware manufacturers offer that we call a sky hook. This is used in conjuntion with universal wave pallets. These sky hooks hold on to the PBC through tooling holes, and keep it from worping. If that doesn't work we go with a selective solder pallet that supports the whole PCB but still allows areas of the board to be soldered. With these tools there hasn't been a board that we can't wave solder. Hope this helps.

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