1
\$\begingroup\$

I was designing the footprint for this FPC connector: Datasheet

The recommended land pattern is shown here:

enter image description here

The issue I encountered is that the pins on one side protrude outside of the pad:

enter image description here

enter image description here

I triple checked the dimensions and the outer "toes" and the "heel" on one of the sides seem fine.

enter image description here

Would the absence of the "heel" fillet on one of the sides be an issue? It's not that I think that Molex has provided a bad footprint but more that I fear I might have misinterpreted something.

enter image description here

Source: IPC-A-610D

Update

These are the measurements on the land pattern depicted above:

enter image description here

I moved the pads to be 2.9mm center to center, and this is the result:

enter image description here

Which is weird, because the long pad is still on the short "pin". Flipping the part to match the long pin with the long pad, this is how it looks:

enter image description here

\$\endgroup\$
  • \$\begingroup\$ Time to get out the digital calipers and see if both the part and the board match the documentation. Anyone doing PCB design work must have a pair on their desk, and it's not like they are expensive anymore - you don't need toolroom machinist level accuracy or traceability. \$\endgroup\$ – Chris Stratton May 13 at 16:27
  • \$\begingroup\$ DWG. says "MISALIGNMENT OF SOLDER TAILS FROM F UPPER DIREVTION : 0.05 MAX. LOWER DIRECTION :0.15 MAX" How much is your result? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 13 at 17:05
  • \$\begingroup\$ @SunnyskyguyEE75 - I think that refers to the coplanarity of the pins on the board, I am worried about the length of the pin vs the pad. \$\endgroup\$ – Wesley Lee May 13 at 17:52
  • 1
    \$\begingroup\$ What is the designed spacing of your pads? The data sheet is confusing, because if read literally the 2.9 mm dimension is not the centerline spacing, but rather somewhat absurdly the spacing from the inside edge of one row to the center of the other. \$\endgroup\$ – Chris Stratton May 13 at 18:43
  • 1
    \$\begingroup\$ That's what it literally says, but measure the part, maybe the dimension was misapplied to the drawing. If you moved your pads so they were 2.9 mm center-to-center, would they better fit the part? If you haven't ordered the boards yet, then by all means try to sort this out before you buy them! Though if that is a 3d model of the part, I'd also want to cross check it for accuracy; once you have a discrepancy you should really be in "believe nothing not personally verified" mode. \$\endgroup\$ – Chris Stratton May 13 at 21:11
2
\$\begingroup\$

Probably not a big deal, since that portion of the pin looks to actually be rounded and not square, which is hard to see in the picture below:

enter image description here Source: https://uk.rs-online.com/web/p/fpc-connectors/7883521/

The dimensions in the datasheet don't show the rounded inside of the connectors which would make it easier to solder and align itself on the pads. I don't know that I'd even worry about if the quantities of the board were low (like 100 or less).

\$\endgroup\$
1
\$\begingroup\$

Your part's data sheet rather dubiously shows 2.9 mm as the distance from the inner edge of one pad, to the centerline of the other. This is highly unusual, and given the alignment mismatch you are seeing, has a strong possibility of being a drafting mistake.

It's not clear what all of the features in your renderings represent, but the first ("unflipped") achieved by assuming that the 2.9 mm is actually a center-to-center distance looks the best of the three (original, adjusted, and adjusted+flipped). If it were me, I would go with that, or at least something based on it.

But more importantly, once a discrepancy is detected, I would "trust nothing" (neither data sheet nor 3d model) and instead personally verify all dimensions with calipers before ordering the boards.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.