| | After rmoving a BGA (plastic)to correct unexplained shorts | | I installed another BGA using flux only. | | Checking on an X Ray machine and found two shorts. | | | | can anyone give a good explenation ? | | | | Thanks | | | | Ron | | | Ron, | It could be a number of factors. Most likely, you had damaged mask in between the BGA pad and via on the substrate. You should also look into your print registration. How are the vias segregated from the pads? Are they tented or is there just a dam in between? Another strong likelihood would be the profile. You can run into a number of problems in BGA rework if the profile is incorrect. An inert reflow atmosphere helps as well. Also, what type of flux did you use? Was it paste flux or was it liquid. You need the tactile strength of paste flux to hold the component in place. If you use liquid flux, the component tends to dance around. | | Regards, | Justin | | Justin,
You young "sea dog" - you just solved my SRT rework problem. You set me straight agout liquid vs. paste flux. Damn you're good and I am either the bad or ugly.
I've been doing S/M touch up for hopelessly mis-registered conditions. Still have some getting through when mask meets specifications. I knew something very dynamic was going on, but hadn't gotten to your conclusions yet.
Thanks a bunch,
Earl Moon
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