Head in pillow at the periphery can also be due to BGA and/or board warpage. I've dealt with two instances where this was the root cause. Inconsistent paste print has bit us a few times too and right now I'm dealing with one where I suspect the copper pattern on the board being the issue. Unfortunatly I haven't dealt with a ball in cup situation yet that could be fixed with the reflow profile. Scott Post P.O.U. 0000-001E-0CTC 2151 E. Lincoln Road Kokomo, Indiana 46904-9005 765-451-2983 (Phone) 765-451-0287 (FAX) -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier Sent: Wednesday, April 21, 2010 3:05 PM To: [log in to unmask] Subject: Re: [TN] Head in Pillow and grapping effects mitigation without Nitrogen Hi Cedric, What do you mean by 'grapping effect"? You do not say where you find 'Head-on-Pillow' defects-they can occur at the BGA periphery and in the BGA center and the root cause is quite different. HOP at the periphery is a solderability issue and certainly involves the choice of paste/flux. HOP in the BGA center means you do not have enough heat there to get the solder ball to a low-viscosity liquid state-that means you need to increase the peak reflow temperature. One of the reasons for larger solder volumes is to achieve greater SJ stand-off heights to improve reliability. Werner -----Original Message----- From: Cedric ORAIN <[log in to unmask]> To: [log in to unmask] Sent: Wed, Apr 21, 2010 2:38 pm Subject: [TN] Head in Pillow and grapping effects mitigation without Nitrogen Hello all, Very fine pitch BGAs (typically 0.5mm) and 0201 chips are becoming common in our company for some months. We recently have to face with new defects type such as grapping effect and head in pillow defect. The solder paste we use has been qualified for even smaller component (WLP, 0.4mm pitch) but in Nitrogen atmosphere. I'm now wondering if this solder paste is suitable with Air reflow. I'm also wondering if a solder paste suitable in that case even exists. Having a look to this study from intel (link hereunder, page 31), I found that the people from Intel are recommending a solder paste volume larger than 2000 mil^3 as a minimum. http://edc.intel.com/Download.aspx?id=3044&returnurl=/default.aspx That is, off-course, impossible for a VFBGA (which solder paste deposit is closer to 900mil^3) but this reading makes me feel uncomfortable. So the question is: is it possible to find out a solder paste which is suitable for VFBGA assembly in Air reflow? If it is not against TechNet rules, have you some solder paste references that you could advise? Here are some additional details: ENIG PCB finition, SAC305 Alloy. Cedric ORAIN Technical Director Electronic Manufacturing Services www.inovelec-groupe.com PS: I'm very new and I'm also French. I wish it will not be too much for you! Anyway, thank for being patient if I have difficulties to understand. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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