Hi Gil,
Why was SnPb soldered at 225 C, per your e-mail, or 230 C per your photo album? In SnPb products, you just need to reach 203 C and if the cap is SnPb, why would you solder it using near Pb free temperatures as the product will not be RoHS compliant anyways? Depending on the quality of the PCB, at 230 C you might even degrade the PCB and, eventually, compromise the pad solderability, with solder going up the component. What finish you have on the pads? Immersion Sn might heavily degrade at high temps.
Also, remember, the molten solder goes towards the high heat. If the pads are connected to ground planes, the capacitor will be hotter and the solder will go up its terminations.
It's not once that I had to prevent solder from going uphill by using lower settings on the topside heaters of the oven and higher on the bottom ones.
Ioan Tempea
-----Message d'origine-----
De : TechNet [mailto:[log in to unmask]] De la part de Zilber Gil
Envoyé : Thursday, May 29, 2014 10:02 AM
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Objet : [TN] Capacitor - strange soldering behavior
Hello Technet,
While soldering this ceramic capacitor (http://ipc-technet.groupsite.com/gallery/27235), its looks like that the capacitor suck the solder from the PCB`s pad to the capacitor pad and the color is now grayish and porosity. XRF found Sn, Pb, Cu on the capacitor pad. PCB solderability was good and the profile was SnPb at 225 deg C under Nitrogen. Other capacitors and components on the board look normal with shine soldering.
Can anybody seen something like that before? Any ideas?
Thanks and have a wonderful weekend.
Dr. Gil Zilber
Technologist, Elta system Ltd.
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