PCB Assembly Services - Screaming Circuits: Speaking of "Not Happy" PCBs...


Speaking of "Not Happy" PCBs...

Pic_uc_bd_blank Speaking of boards with issues, this one (click the image to enlarge) used in my prior post has a few more problems than just holes that are too small. Other than the holes, it is serviceable, but it really isn't a great PCB. It's a immersion silver board from an off-shore manufacturer. This house is not a place we would ever send our customers.

One of the most obvious issues is the registration of the silk screen. For example, Look at the nomenclature for "C6". Half of the "C" is right on top of the pad for pin 18 Yucky_brd_c6 of IC2. You could scrape it off, maybe or you could hope that the enough solder would flow under to make a good connection, but it isn't a good situation. In the CAD package, the label was not on the pad but the board house used a slightly larger font size and the registration was off a bit. One more thing for your design check - make sure that you have plenty of clearance in case the board house does what this one did to me.

Yucky_brd_i2c Sometimes, it's the library again. Looking at X6, the I2C connector, one of the silk screen lines trims the top of all four solder pads. The library part in the cad package does that so I should have caught it.

The last comment I have about this board concerns the drill holes. Look at the ridge around the holes here on. All of the drilled holes had that ridge to a certain degree. It's not catastrophic in a prototype environment, but it speaks to a few processing steps left out at the board house

Duane Benson


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