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I am recently bump into a problem where we found a certain percentage fallout of the open via. This is my very first time seeing this kind of problem and don't really have an idea why. It comes back from failure analysis with some images as posted. The first image looks like a corrosions on the copper plating while second image, the copper is totally open. I am checking the via plating thickness and it is within the spec. Some are saying it is caused by the copper plating during PCB fabrication but anyone please advice and explain what could be possibly causing all these issues? Supplier is blaming on the flux we are using.

Thanks in advance!

Image#1: Image#1

Image#2: Image#2

Image#3 Image#3

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    \$\begingroup\$ Unless someone has seen and analyzed the exact same thing, it is mostly guesswork that can be done here. Looking at how that inner layer got torn apart too, I would guess its some physical stress that rips stuff aprt. \$\endgroup\$
    – PlasmaHH
    Dec 18, 2014 at 13:26
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    \$\begingroup\$ Before or after reflow? Is your Stackup symmetrical? Put the board on a flat surface see any cupping/ potato chipping? What's your stack and surface finish. Then check out this article on via cracking from ipc ipcoutlook.org/pdf/… \$\endgroup\$ Dec 18, 2014 at 13:55
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    \$\begingroup\$ On a second thought, we can not tell much about how that crossection was created, so the ripping apart could also be a result of not being careful enough there. \$\endgroup\$
    – PlasmaHH
    Dec 18, 2014 at 13:55
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    \$\begingroup\$ We used to see this now and then with dodgy Asian suppliers (Taiwan was the bad guy back then). I think (guess) it's bad process control (probably dirty chemicals) in the activation or electroplating process. Flux? Well, they have to say something. As @PlasmaHH says, the cross-section doesn't look great- there is evidence of delamination and ripping in the second photo. The problems we found were cracking (all the way around) at the top and bottom 'corners' between the through-hole plating and the top and bottom layers. Unless you have a big incentive to keep using these jokers, I'd move on.. \$\endgroup\$ Dec 18, 2014 at 14:38
  • \$\begingroup\$ It is actually after reflow. All these were found when it gone thru test. It is odd that there are a couple of boards cross sectioned and all of them having the cracks like in the layer around the opened via. And also for the first picture, I wonders if that possibly caused by etching chemical (dumb) \$\endgroup\$
    – yun
    Dec 19, 2014 at 0:14

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Supplier is lying to you, and hoping he can get away with it. The second picture shows damage both to the layer bonding agent (left picture) and the substrate itself (right picture). I'm no expert on PC fabbing, but the second picture looks like they used a badly defective drill bit to make the holes. It's the only explanation that comes to mind which would explain that sort of tearing, although defective substrate stock might do it for the right-hand picture. I can almost accept the flux explanation for the first picture, but not the second.

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    \$\begingroup\$ Yup -- no way the company will voluntarily try to make this right. You'd have to be a little crazy to use them again, so they know they have little hope of retaining the customer here. \$\endgroup\$ Dec 18, 2014 at 22:48

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