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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


#10841

paste in hole | 24 June, 1999

hello,

has anyone tried dispensing solder paste in thru holes instead of waving or hand soldering. if so how did it work out for you. thanks for the input

wayne

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Earl Moon

#10842

Re: paste in hole | 24 June, 1999

| hello, | | has anyone tried dispensing solder paste in thru holes instead of waving or hand soldering. if so how did it work out for you. | thanks for the input | | wayne | | | Once you start, depending on applications, you'll toss your wave solder machine forever!!!

Earl Moon

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Scott Davies

#10843

Re: paste in hole | 25 June, 1999

Wayne, Earl,

I wish there was some way we could toss our wave solder machine forever! Unfortunately, we haven't found a way yet to do paste-in-hole reflow for large numbers of thru-hole axial and radial components, which we insert on Universal machines.

However, the work we have done with hand loaded pin in paste components has been very successful. After some early problems, we are now achieving near 100% success rate. The most significant influences have been stencil aperture increases, hole to lead ratios and varying the print parameters to ensure that enough paste is forced down the hole, almost completely filling it.

In addition, be aware that some thru-hole components are not suitable for withstanding the temperatures inside a reflow oven; we've had a few electrolytic caps fail on us for this reason.

Best of luck Scott Davies

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Christopher Cross

#10844

Re: paste in hole | 25 June, 1999

| hello, | | has anyone tried dispensing solder paste in thru holes instead of waving or hand soldering. if so how did it work out for you. | thanks for the input | | wayne | | | We have tried this mainly on thru hole connectors (.035 pins, .1 spacing with .040 holes)and have had a great deal of success. the most important elements are the stencil aperature and the pin/hole size ratio. Our connectors are placed by hand so the operators needed to use a little caution not to push the connector in too hard or too fast and push the majority of the paste out of the hole and onto the bottom of the lead or on the floor even.

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John Thorup

#10845

Re: paste in hole | 25 June, 1999

| | hello, | | | | has anyone tried dispensing solder paste in thru holes instead of waving or hand soldering. if so how did it work out for you. | | thanks for the input | | | | wayne | | | | | | | We have tried this mainly on thru hole connectors (.035 pins, .1 spacing with .040 holes)and have had a great deal of success. the most important elements are the stencil aperature and the pin/hole size ratio. Our connectors are placed by hand so the operators needed to use a little caution not to push the connector in too hard or too fast and push the majority of the paste out of the hole and onto the bottom of the lead or on the floor even.

Gentlemen I have been planning to try this for a 96 pin right angle DIN connector in an upcoming product. I would appreciate your comments about pin/hole ratio, stencil aperture, stencil thickness, etc. thanks|

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Jeff Strumpf

#10846

Re: paste in hole | 25 June, 1999

| | | hello, | | | | | | has anyone tried dispensing solder paste in thru holes instead of waving or hand soldering. if so how did it work out for you. | | | thanks for the input | | | | | | wayne | | | | | | | | | | | We have tried this mainly on thru hole connectors (.035 pins, .1 spacing with .040 holes)and have had a great deal of success. the most important elements are the stencil aperature and the pin/hole size ratio. Our connectors are placed by hand so the operators needed to use a little caution not to push the connector in too hard or too fast and push the majority of the paste out of the hole and onto the bottom of the lead or on the floor even. | | Gentlemen | I have been planning to try this for a 96 pin right angle DIN connector in an upcoming product. I would appreciate your comments about pin/hole ratio, stencil aperture, stencil thickness, etc. thanks| | We typically recommend this formula for determining the paste volume needed: (Hole volume - Pin volume) x 2 - Remember, only half of the paste is metal - Use pie(r2h) for hole and pin volume - Be sure to calculate only the volume of the pin that will be in the hole - Some folks add ~10% more paste to account for any "drop out" and to build solid fillets. |Once you know your target volumes you know how to design your stencil. Dont't be afraid of printing off the HASL, the solder will draw towards the hole during reflow. When fine pitch surface mount components are also being printed, you may need to"step" the stencil so that you have the thickness you need around the holes to give you adequate paste. Good Luck.

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Christopher Cross

#10847

Re: paste in hole | 28 June, 1999

| | | hello, | | | | | | has anyone tried dispensing solder paste in thru holes instead of waving or hand soldering. if so how did it work out for you. | | | thanks for the input | | | | | | wayne | | | | | | | | | | | We have tried this mainly on thru hole connectors (.035 pins, .1 spacing with .040 holes)and have had a great deal of success. the most important elements are the stencil aperature and the pin/hole size ratio. Our connectors are placed by hand so the operators needed to use a little caution not to push the connector in too hard or too fast and push the majority of the paste out of the hole and onto the bottom of the lead or on the floor even. | | Gentlemen | I have been planning to try this for a 96 pin right angle DIN connector in an upcoming product. I would appreciate your comments about pin/hole ratio, stencil aperture, stencil thickness, etc. thanks| | | I attended a seminar where Phil Zarrow was a speaker and he gave the following formulas to use as a guideline for paste in hole components:

Procedure for determining the solder stencil aperture size (print area) for through-hole components

Known information: Component lead size, Stencil thickness, and Inspection factor

Determine board hole size based on lead size: Round lead hole size = maximum diameter + .012" Square or rectangular lead hole size = maximum diagonal measurement + .010"

Formula:

H = Hole diameter D= Lead diameter T = Board thickness L = Width of lead in the X direction W = Width of lead in the Y direction p = 3.14 Hole Volume (HV) = (p)(H/2)(H/2)(T) Lead Volume (LV) = (p)(D/2)(D/2)(T) (for round leads) Lead Volume (LV) = (L)(W)(T) (For square or rectangular leads)

Required solder volume (SV) = HV - LV

Required Print Volume (PV) = (2)(SV) (50% shrinkage during reflow)

Required Print Area (PA) = (F)(PV)/stencil thickness

F = Inspection factor .7 = no fillet .9 = fillet on both sides .8 = fillet on primary side 1.0 = large fillet on both sides

I have been using this as a guideline for all the work I have done so far, I have fudged the aperature size up somewhat from the formula comes out to in most cases - just to get me in my own comfort zone as far as the fillet goes. We are generally doing .100" spaced connectors/headers and most have turned out with good solder joints and nice fillets. The aperature size I am using for these is .085" sq pads around each .035-.040" hole (6 mil stencil). I have also found that pin/hole ratio is most important - you'll see what I mean after you plug some different combinations into the formula - we had some dense connectors(100pin 4 row - .08 spacing) were the pin/hole ratio was so small (using vendor recommended hole size)that we couldn't put down enough paste to fill the hole and at the same time couldn't make the hole any smalller or insertion would become difficult getting the pins to line up. Good Luck!!

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