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pre-heat settings for wave solder

#3744

pre-heat settings for wave solder | 20 June, 2000

Can anyone give me a ballpark figure on where to set the temperature for the pre-heaters of a wave solder? Any responses are greatly appreciated.

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#3745

Re: pre-heat settings for wave solder | 20 June, 2000

Gary: Your flux supplier is the person for you to ask this question. For instance, the Lonco Superflo 26F that Jason was talking about last week has a preheat of 85�C to 110�C. * Thickness and number of layers of your board will affect you choice of preheat. * Consider is trying to maintain the delta T between preheat and wave to LT 100�C

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gary

#3746

Re: pre-heat settings for wave solder - Hi Dave F ! | 20 June, 2000

How to calculate the delta T ? What's the allowable range for delta T value? we r not calculating this in our process, instead we r maintaining the pre-heat temp which we measure from topside of the bd.

Thanks in advance

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#3747

Re: pre-heat settings for wave solder - Hi Dave F ! | 20 June, 2000

Hi Gary: I'm sorry for not being clear. You should be concerned about the change in temperature between the end of preheating (actually just before the wave) and the wave. So, it is the difference between those two temperatures you should try to keep under 100�C. Some would say 80�C. So, what it!!! Dave

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#3748

Re: pre-heat settings for wave solder - Hi Dave F ! | 21 June, 2000

Hi Dave,

how does that calculate when you consider a topside temperature of for example 120�C like mentioned for NC-flux a while ago and a pot temperature of 250�C ?

Just wondering

Wolfgang

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#3749

Re: pre-heat settings for wave solder - Hi Dave F ! | 21 June, 2000

Wolfgang: You're correct, I've obviously goofed this up, somehow!!!

(sound of scurrying in yellowed soldering notes)

Let me try and find the source for this to redeem myself.

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gary

#3750

Re: pre-heat settings for wave solder - Hi Dave F ! | 21 June, 2000

my topside preheat is 97 deg. C and my peak temp. is 230 deg. C with a duration of 4 secs. What would be my Delta ? I suppose 230 minus 97 is equal to 133 deg C...is that right?

regards

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C.K.

#3751

Re: pre-heat settings for wave solder | 22 June, 2000

TYPE of Preheater makes a HUGE difference, as well. Infrared (IR) and convection, 2 of the most common types of preheaters, have very different heat transfer characteristics.....

Convection heats your board more uniformly, so you'll see very small variance between bottom and top-side substrate temps....your preheat settings will be significantly lower with a convection system.

IR preheats are more sensitive to board / component thickneses, and need to be tweaked based on those (more recipes). You'll also see higher temperature gradients throughout your board - especially assemblies with massive, heat-sinking components, ground planes, and/or thick, multilayered....

...and lastly, you need convection preheat if you're running a water-based flux....

...Also, search both the SMTNet archives and the library - there's lots of good information there from very knowledgable people on this topic.

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Boca

#3752

Re: pre-heat settings for wave solder - Hi Dave F ! | 22 June, 2000

Everybody's right!

Two concerns are proper preheat for the flux and reduced thermal shock to surface mount components. The stupid er dumb thing is that these can be at odds with each other.

The flux vendor usually specs topside temp before wave. The component vendor usually specs max rate of temp change thru the process. If you satisfy the component vendor you may be heating the fab over the temperatures recommended by the flux vendor. What to do oh what to do.

One way to approch this; If the assembly has no surface mount on the solder side, target the flux vendor specs. If the assy has small SM components on the SS, target the flux vendor specs. If the assy has larger SM passives (larger than 1206 multilayer caps) or has a history of cracked capacitors, target the component vendor. And watch for other solder defects related to overheating the flux, such as bridging and so on.

HIH

Boca

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#3753

Re: pre-heat settings for wave solder - Hi Dave F ! | 23 June, 2000

Gary: According to what I was try to say, you have read me correctly.

NOW ... I would not pay much attention to my 100�C delta T babbling. It is in our work instruction for setting-up the wave, but no one pays attention to it. And I, nor anyone else can find a source for it. Our best guess is that it's a guideline that suggests keeping the delta T from top to bottom of the board.

Good luck

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#3754

Re: pre-heat settings for wave solder - Hi Dave F ! | 23 June, 2000

Hi Boca,

that sounds reasonable, but if we talk about dT that the SMD component on the solderside sees that�s a lot smaller than dT on the topside. So the only guess I can make is that the dT Dave mentioned has to be seen for the component on the solderside. Your rules of thumb sound applicable and in the end the results are counting.

Wolfgang

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Super K (Evil K)

#3755

Re: pre-heat settings for wave solder - an answer to Gary's ? - Hi C.K. (Mini K)! | 23 June, 2000

To answer Gary's question:

Gary, you will need a production board, thermal profiler, flux vendors product data sheet on the flux you intend to use, maybe your wave vendor service engineer or wave solder vendor contact (unless you know your wave) and component thermal info.

1. Your flux data sheet should have the required preheater temperature for the topside of your board and possibly for the bottom too. It should also have the maximum temperature ramp rate (generally for components). Some even have recommended conveyor speeds and contact time in solder, along with solder pot temps. Use this as your guide to initially set-up your wave.

2. Ask your wave solder vendor what he recommends the preheaters be set at to meet your flux's data sheet with your size board. Make sure you know the dimensions of the board, thickness and number of layers.

3. Next attach thermocouples from your profiler to your board. I won't get into how or where to put them, unless you want me to.

4. Run board and profiler through wave. If you don't know what RPM to set your wave(s) at, leave em low. All you're looking for right now is preheat temps.

5. Grab hot board from other end of wave (key word here is HOT) and use the profile generated from your profiler software to make adjustments to your wave so you meet the flux vendors data sheet.

It may take a couple of passes through the machine with the profiler, but you should be able to meet the data sheet within a day, depending on your experience and profiler.

6. Set-up the wave portion of your wave until you have good contact between your board and wave(s). Next run the board and profiler though the entire process.

Congrats, you should have all the thermal info you need on your wave!

As for the above jargon with regards to delta-t and parts, a simple rule of thumb for most waves is there will always be a drop in temperature between the wave pot (contact with wave). I try to set my last preheater as the hottest one to keep delta-t a minimum. I know this by using the profiler!

Once you get your process set-up, compare your profile your component vendors profile (yes, they do have them) and make sure your process meets this profile. It probably will, but always make sure, especially the delta-t between the last preheat and the wave!

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Super K (Evil K)

#3756

Re: pre-heat settings for wave solder - an answer to Gary's ? - Hi C.K. (Mini K)! | 23 June, 2000

To answer Gary's question:

Gary, you will need a production board, thermal profiler, flux vendors product data sheet on the flux you intend to use, maybe your wave vendor service engineer or wave solder vendor contact (unless you know your wave) and component thermal info.

1. Your flux data sheet should have the required preheater temperature for the topside of your board and possibly for the bottom too. It should also have the maximum temperature ramp rate (generally for components). Some even have recommended conveyor speeds and contact time in solder, along with solder pot temps. Use this as your guide to initially set-up your wave.

2. Ask your wave solder vendor what he recommends the preheaters be set at to meet your flux's data sheet with your size board. Make sure you know the dimensions of the board, thickness and number of layers.

3. Next attach thermocouples from your profiler to your board. I won't get into how or where to put them, unless you want me to.

4. Run board and profiler through wave. If you don't know what RPM to set your wave(s) at, leave em low. All you're looking for right now is preheat temps.

5. Grab hot board from other end of wave (key word here is HOT) and use the profile generated from your profiler software to make adjustments to your wave so you meet the flux vendors data sheet.

It may take a couple of passes through the machine with the profiler, but you should be able to meet the data sheet within a day, depending on your experience and profiler.

6. Set-up the wave portion of your wave until you have good contact between your board and wave(s). Next run the board and profiler though the entire process.

Congrats, you should have all the thermal info you need on your wave!

As for the above jargon with regards to delta-t and parts, a simple rule of thumb for most waves is there will always be a drop in temperature between the wave pot (contact with wave). I try to set my last preheater as the hottest one to keep delta-t a minimum. I know this by using the profiler!

Once you get your process set-up, compare your profile your component vendors profile (yes, they do have them) and make sure your process meets this profile. It probably will, but always make sure, especially the delta-t between the last preheat and the wave!

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gary

#3757

Re: pre-heat settings for wave solder - Hi Super K | 25 June, 2000

thanks for the feedback....but what's your delta T and how will you know that you are within the delta T range ?...I think this is the main point of the above topic...can you elaborate more on how did your company get Delta T ?

thanks and regards,

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Michael Parker

#3758

Re: pre-heat settings for wave solder - Hi Super K | 26 June, 2000

I belive I once saw a picture of a Delta-T. It was in a very old Popular Science magazine. Some yahoo from Ohio wanted to put wings on his ol' tin lizzy. He also had some elaborate plans to convert his flat head V-8 to run off corn likker. I say chuck the old Ford, chug some of that hi-test straight from the jug, start flappin yer arms and soar like an eagle!!!

It could happen, trust me

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Tekguy2000

#3759

Re: pre-heat settings for wave solder - Hi Super K | 26 June, 2000

Then if you have R-Paks on the solder-side start all over again!!

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