How does chip automounter /reflow work?

[ahgu]

does it glue the chip?

and how does reflow work? dip into a bucket of molten solder? or let molten solder flow thru the board? But how does the chip stay on top at 250degrees?

thanks
ahgu

 

[AN]

Please read:
**broken link removed**

 

[Encrypted]

For Reflow:

First a screen is used to place a layer of solder paste over the pads. Then a pick and place machine places the parts onto the PCB. The PCB then goes through a relow oven which melts the solder and makes the joints.

Parts are not glued as the surface tension between part and paste holds them in position.