Hi Guys,
So I work for a small contract manufacturer which caters mainly to the defense sector. As such, our customers haven't (yet) had a great need to incorporate 01005's into their designs. Looking forward, we decided to "take the plunge" and dial in a process ahead of the requirement. So we purchased a dummy test kit (Practical Components - PC2009 AIM Solder Print Test Board and Kit). This kit has everything from 01005 resistors on up to a BGA388.
We ordered a lead-free kit (ENIG FAB finish) so as to challenge ourselves as much as possible. Using Ekra Printers, MYDATA Placement equipment and a new Vitronics XPM3i 820 Reflow Oven (eight zones, 264cm/104" of heated length, Air - Nitrogen is not an option as our infrastructure will not permit it... to say nothing of the cost). Paste is Alpha WS-820 Type 4 (ORH0).
First off, let me state that we have no problems with the printing or the placement of the 01005's (or any of the other components). Paste transfer, release and volume is excellent - 85-95% coverage of pad area at the critical 01005 pad sites (3mil foil, Fine Grain Steel with the DEK Nano-Coating). The 01005's are placing (and reflowing) on pad in perfect alignment. So printing and placement are not a problem to this point.
The reflow is the main issue I'm having with these (and only the 01005's) parts. More specifically, "Graping" of the solder joints. All of the other parts in the population from the 0201's on up to the largest BGA look great.
I've tried multiple profiling strategies using our KIC Explorer. RSS (1.25c/sec. Max Rising Slope, 67sec. soak 130c -180c, 70sec. TAL, 245c peak temp), RTS (1.15c/sec. Max Rising Slope, 62sec. TAL, 245c peak temp). preceeding profile results were averages from each profile type.) Believe it or not, the RSS profile produced marginally better looking joints on the 01005's. "Concave Graping" instead of just balling up at the termination.
I have contacted Alpha and await their response. So I wanted to ask you, what would you guys suggest for profile parameters (Max Rising Slope - Ramp Rate, Soak?, TAL, Peak Temp) when trying to develop a sucessful reflow strategy in AIR?
Thanks for any/all feedback.
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