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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Can anyone recommend a reflow profile for already flowed solder?

#28168

Can anyone recommend a reflow profile for already flowed solder? | 21 April, 2004

As one of our small batch processes, we place BGAs on PCB without using solder paste. We apply tacky flux to a predetermined height on a pallet, "dip" the BGA into the tacky flux to wet the solder balls to the set height, and then use a BGA rework station to place the BGA on the pads. We X-ray placement accuracy, and then reflow.

The problem I am encountering is that I do not have any documentation suggesting a preferred reflow time/temperature curve for the already flowed solder balls of the BGA. Using a solder-paste reflow profile as a guideline (such as Kester R562) of course doesn't work well because it is for fresh flux-impregnated paste, not for already flowed solder. I have devised profiles that work, but I'd like to hit the nail on the head, and reduce the risk of thermal harm on my components.

Does anyone have a profile they would recommend for time/temperature on a 7 zone convection oven for BGA solder ball reflow?

Thanks in advance, John Patricelli Analog Technologies Corp.

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RDR

#28174

Can anyone recommend a reflow profile for already flowed solder? | 21 April, 2004

We always use the regular production reflow profile when we use this method. Since you don't want to do that, All that is required is to ramp the part up to temp to get the balls to melt. If you don't exceed 2C per sec. in a ramp you will be fine. and also make sure that you do not exceed the max temp that the part can withstand.

As a thought/observation: Don't we usually try everything in our power with rework stations to get them to run a normal oven type profile?

Russ

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pjohnson@volterra.com

#28175

Can anyone say NOT to use my reflow profile??? | 21 April, 2004

Simple process - we use similar Kester solder brands of "no clean" low residue solder wick to clean our pads, then brush with isopropyl, and apply Kesters brand of tacky flux under a Leica 6x microscope. We do this on 7x7mm and 9x9mm packages. This works well with our failures from test, where we use BGA pre-form solder quik reballing templates.

In feedback from engineers I have not had any reports of thermal failure in logic ICs or passive/active components. The neat part is that I don't require a BGA camera or scope to peer 3-4 rows in for alignment, the natural tension generated by the "flowing" solder pulls it into place. ----------------------------------------------------------

John here at Volterra we use a standard reflow profile for our BGA rework & placement. I like the reflow oven for consistent results, it's a 4 zone convection oven. Our boards go 4-7 layers, 1"x4" modules up to load boards going 8"x12". All have a mix of 402/603 caps/res and usually have inductors plus fuses/diodes/in mixed packages.

160 170 190 270 top heaters 160 170 182 250 bottom heaters

Belt speed set between 17-19 resulting in a 4:20 - 4:30 min/sec profile. Thermal profiling on the curve reads 175` at start of 3rd zone and peaking in 4th zone at 225` C .

Regards, Phil Johnson Senior Engineering Technician http://www.volterra.com/

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Ken

#28177

Can anyone recommend a reflow profile for already flowed solder? | 21 April, 2004

It makes no difference if the solder is in balls, ingots, bars, paste etc. The thermal profile satisfies key areas of the reflow process as a function of your flux and alloy type.

Peak and duration above liquiduous are a function of the alloy. preheat and soak periods are a function of your flux.

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#28201

Can anyone recommend a reflow profile for already flowed solder? | 22 April, 2004

bunmiog

#28202

Can anyone recommend a reflow profile for already flowed solder? | 22 April, 2004

Reflow Oven

reflow oven profiler