wave soldering
For wave soldering the PCB passes over a bath of molten solder where the solder is pushed up so that it strikes along the bottom side of the PCB. You'll need a solder resist mask to prevent to have solder over all the copper. 

Note that also SMDs can be wave soldered, but then the orientation of the parts is important. Some parts have to be placed perpendicular to the wave direction. Fine pitch parts like 0.4 mm QFPs can't be wave soldered because all the pins will be shorted, but QFPs with a higher pitch can. They need "solder thieves", which are solder pads at the end of a row of pins to gather residual solder.

  

A QFP may have to be placed at a 45° angle, and will have the solder thieves at one of the corners:  



The wave direction is important during PCB layout and panelization, and the production engineer should get clear instructions on it.

reflow soldering
SMDs for two-sided placement are glued on one side. After solder paste is applied with a stencil a glue dot machine places glue dots for the parts (at an incredible rate of more than 10 per second). Then the parts are placed, the panel is flipped over, and the other side gets solder paste and component placement.  

Questions on mass-production soldering
I want to write my first Java program, for example Phonebook, and I wonder what to do first. My question is should I write GUI classes first or util classes first?
I am database developer and want to know best practice in building program.
