Anablog

So I went to drop off some letters around the corner and as I walked around the block I came upon these three circuit boards in the gutter of the road. Only in Silicon Valley do you find road-kill like this. The boards are all scuffed up but that is no reason not to learn from them. You can click on the images for a bigger view.

The road-kill I found in the gutter. The middle one is a JDS Uniphase board. Neat routing and very sophisticated. The top and bottom boards are nice WinSystems single board computers. The boards are covered with scuff marks from tire tracks, just ignore that damage.

Here is a close-up of the JDS Uniphase board. Note how it is routed out with breakaway tabs. This allows a nice rectangular board for the board house to send through the solder machine and maybe even into a test fixture. Once everything is inspected and OK they can break the board out of the outside. Notice the “thieving” the squares of copper on the outside areas. On inner layers it allows the laminate glue to flow and balance, on the outside layers it evens the acid etch and reduces warping. The local fab house, Proto Express has started to add this thieving to blank areas on their no-touch boards. Problem is us analog guys often really want no copper under some low-capacitance nodes. Proto Express told me to send a note with the board to not add thieving or it will be added automatically. Also note the tool-holes in the corner of the board. These tool holes hold the many layers in alignment while the layers are being laminated together. And there is a target —the little solder dot that is just diagonally inside the tool-hole. Note there is a target on the rounded corner of the routed out layer too. This is for lining up laminate layers and for registration of the pick-and-place machine that puts the parts down on the board in assembly.

Here is why the WinSytems board was in the gutter— this tag was still on it. It failed optical inspection. A darn good board house or assembly house did this inspection. Why assemble a marginal board with valuable components? Trash the board and save the risk folks.

Another shot of the JDS Uniphase board. The yellow sticker might mean it failed electrical test. I don’t see anything visually wrong with this net, but it may be open or shorted inside the board.

What a nice fan out.

Another fan-out.

Here is the interesting footprint on the back of the JDS Uniphase board. Anybody know what this does?