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THE ETHERNET DEVELOPMENT BOARD

Part 1: Putting it all Together
by Fred Eady

Start ý Overview ý Elmerýs Silicon Glue ý Time to Kill ý The CS8900A-CQ ý Software and Firmware ý ICSP and LVP ý Assemble the Ethernet Electronics ý No Floating Allowed ý Installing the Bypass Capacitors ý Pin Point ý Finishing Installation ý Assemble the PIC16F877 Electronics ý The Rest of the Project ý Winding Down ý Finishing Up ý Sources and PDF

NO FLOATING ALLOWED

Another SMT construction essential is solder paste. For the record, I use Alphametals no. 8 solder cream. Not only does the solder paste aid in the soldering process, it also helps to hold the smaller components in place until you can apply heat. Notice that, in Photo 4, I applied the paste liberally but didnýt get as happy with the solder paste in certain areas. Through-hole connectors and pads for voltage regulators donýt need the paste treatment. And, while weýre on the subject of larger parts and connectors, the Metcal soldering system allows for easy tip changes.

Photo 4ýDonýt use too much paste on the smaller components. It makes them "float" and causes them to be difficult to hold down and solder.

While I was in the solder system purchase mode, I obtained some through-hole tips as well. I found out the hard way that you can easily ruin an SMT tip by using it for through-hole work. The CS8900A-CQ should be tacked down before you apply the solder paste. If youýre OK with the positioning of the CS8900A-CQ Ethernet IC, slap some solder paste on your printed circuit board and carefully solder in the IC. You shouldnýt need to add any solder to the process. The printed circuit board pads should have enough solder to allow the CS8900A-CQ pins to bond to their pads. The Metcal soldering tip I suggested fits nicely between the pins of the CS8900A-CQ. By placing the tip between the pins, I generated enough heat to actually solder both pins and not bridge the connection between the adjacent pins.

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