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Improving PTH fill using select solder

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Improving PTH fill using select solder | 14 May, 2012

I am a user of an Ersa Versaflow 3/45. I was wondering if anyone could share some process pointers.

I have a 0.125" multilayer PCB that I am having problems consistently achieving 75 percent hole fill on a mini-coax connector. The coax connector has four pins that are 26 mils in diameter and a center pin that is 15 mils in diameter. The board has four layers of 2 ounce copper and it is a very efficient heat sink. Initially started with our regular flux and a topside temp of 95C and a solder time of 6 seconds. Found by trial and error that we needed to increase the topside preheat temp up to 150 C to help with PTH fill. This caused us to change to a hand brushed Tacflux since it could withstand these preheat temperatures. We also increase the solder dwell from 6 yto 10 seconds. That has helped the yield but we still get about 25% of the small center pins as not having enough solder. What is strange is that you can see the gold on the center pin while the four outer pins are all soldered and exhibit good wetting and solder fill.

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Improving PTH fill using select solder | 14 May, 2012

You're thinking correctly in trying to improve your process. Can you change to a more active flux?

Look at the copper that connects to the center pin. You may need to relay-out the board to add a wagon wheel style thermal relief in that area.

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Improving PTH fill using select solder | 18 December, 2012

In those cases where we have a 3.2mm thick, 16-layer board with several GND layers, do we still need ground connection to each and every layer (with thermal relief) or, skip part of the ground patterns? Will it help soldeing rising. I can't reach more the 20% barrel fill.

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Improving PTH fill using select solder | 19 December, 2012

Many times we manually add flux from the top side for good fill.

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Improving PTH fill using select solder | 19 December, 2012

What is your solder pot temperature? We found that on a 0.093" multilayer board increasing the temp of the lead free solder from 300C to 315C helped with the barrel fill.

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Improving PTH fill using select solder | 19 December, 2012

have you considered intrusive reflow? I ran a product similar to what you are describing and the only way we could get sufficient holefill consistently was by this process....

there may be obvious reasons why you cant but worth a shot if you can- it saved me a lot of headaches!

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Designers Are Babies | 19 December, 2012

MosheSh: When it comes to ground planes, most designers are out over their skis. They don't understand what's going on or how it affects their design. So, they get massively conservative about the number of plane layers, whether they can be hatched or not, whether the plane has to cover the entire layer, etc

So, it ends-up being one of those "I shot it. You skin it and cook it situations."

Not all copper pours are ground planes. Here are some links to articles on designing ground / shield / etc planes * Best Practice In Circuit Board Design, Tim Jarvis BSc CEng MIEE MIEEE KTL-Hull

* Bypassing, Decoupling, SHIELDING, and Groundplane

* Design Considerations for Mixed-Signal - How to Design a PCB Layout

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