Frank,
what you have to consider when choosing a solder paste is particle size.
You want approx 5 particles minimum across the smallest aperture. So in your
case, 0,014 dia, which equals to 0,35mm gives us 0,35/5=70 microns. That
means that you will be fine with a standard Type 3 paste (see J-STD-004).
A Type 4 paste will give you better definition of the print. But you will
pay that with higher price and risk of possible process problems.
A 5 mil (125 microns) or even 6 mil (150 microns) stencil will work as your
aspect ratios would be 0,35/0,125=2,8 and 0,35/0,150=1,75. Minimum 1,5.
(IPC-7525) 4 or 5 mil will provide better release.
Alloy and flux type is depending on the intended production process and end
item environment. In my opinion the Senju pastes does a good job. Number of
layers does not play a role when choosing solder paste.
Is the CSP bumps really 0,014" dia? Sounds large to me. You may want to
double check that.
regards
Björn Kullman
Training Manager
Sincotron Technology Center, Norrköping, Sweden
Sincotron Sverige AB www.sincotron.se
phone +46 (0)11-368288 mobile +46 (0)70-4245607
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]]För Francis Sun
Skickat: den 13 maj 2002 16:13
Till: [log in to unmask]
Ämne: [TN] Recommended solder paste for a 6 layer double-sided board
with CSP & BGA packages
Hi,
I would appreciate any recommendation and/or feedback on solderpaste for a
6 layer double-sided board with CSP & BGA packages.
The smallest aperture size is 0.014 inch dia. for the CSP.
TIA.
Regards;
Frank Sun
IVHS
(905) 624-3025 ext. 1235
Fax: (905) 624-4572
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