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I was intending to use the Lumberg 1503 02 3.5mm stereo jack connector on a PCB. After progressing some way through the design, I noticed that the pins for the connector are not on the bottom as I expected, but ~1.5 mm up the body. The rear pins also have a strange bend in them.

Based on the 3D model, I can identify three possible places where the connector could sit on a PCB:

Read view of connector showing possible PCB locations

I have highlighted the rear legs as they don't show up well otherwise.

From top to bottom, the green lines show possible PCB locations:

  1. The PCB sits flush with the pins. This required a cutout for the body as well as the rear pins where they drop down.
  2. The PCB sits flush with the lowest point of the rear pins. This required a cutout for the body and the front pins are in mid-air.
  3. The PCB sits flush with the lowest point of the body. All pins are in mid-air.

Option 1 seems the only viable choice, but the datasheet makes no mention of a cutout, only standard PCB pads and holes for the locator pins.

What am I missing and how do I correctly design a PCB footprint for this connector?

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2 Answers 2

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enter image description here

Looking at the datasheet for this jack, I suspect that this jack is intended for through-board mounting. (Some manufacturers call it mid-mounting.) The body of the connector goes into a cutout in the board. The pins solder to he pads next to the edges of the cutout. The pads may be either the top or the bottom of the PCB. The advantage of through-board mounting is that it removes the PCB thickness from the overall height of the PCB assembly (if the jack is the tallest component).

What function do the plastic pegs serve in a through-board configuration? They are an atavism from another variant in this connector family. The manufacturer had reused the plastic injection mold which had the pegs.

p.s.
The drawings for this jack are rather poor. If it were my project, I would be looking for a jack with a better datasheet. Mechanical problems in PCB layout are hard to patch. Why take a risk.

Here's a similar jack which shows through-board mounting in more detail:

enter image description here

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  • \$\begingroup\$ the pegs could be to help ensure alignment during reflow soldering \$\endgroup\$ Commented Apr 26, 2019 at 23:04
  • \$\begingroup\$ @Jasen In a through-board (mid-mount) arrangement, the plastic pegs don't touch the PCB. \$\endgroup\$ Commented Apr 26, 2019 at 23:15
  • \$\begingroup\$ some sort of tray could be used. \$\endgroup\$ Commented Apr 26, 2019 at 23:21
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The round prongs are plastic. They only serve mechanical purposes; they are possibly even designed to be "smushed" by a hot device so to strongly affix the plug to the PCB.

So, the metal pads that actually are connections need to be flush with the PCB for solder contacting; so, only your option 1 is logically feasible.

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    \$\begingroup\$ The technical term for "smushed" is staking. This connector is designed for very low-profile products, where they can't afford to have the full height of the jack above the PCB. \$\endgroup\$
    – Dave Tweed
    Commented Apr 26, 2019 at 19:58
  • \$\begingroup\$ Yeah I get what the plastic pins are for, I just couldn't see any information in the data sheet about needing cutouts in the PCB and I didn't want to assume anything. \$\endgroup\$
    – jfowkes
    Commented Apr 26, 2019 at 20:00
  • \$\begingroup\$ The plastic pegs on typical SMT connectors are mainly for mechanical alignment during pick&place and reflow. These pegs aren't intended for staking. They are usually about 1mm tall, and they don't protrude on the other side of the PCB. (Notice that the PCB thickness on the O.P. drawing isn't to scale.) \$\endgroup\$ Commented Apr 26, 2019 at 20:28
  • \$\begingroup\$ @DaveTweed Is there a difference between staking and riveting? \$\endgroup\$
    – Hearth
    Commented Apr 26, 2019 at 20:31
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    \$\begingroup\$ Staking is generally a feature built into the part's plastic molding, while riveting generally refers to a separate part (a rivet, usually a hollow metal tube) that is added to the assembly. The ends of the tube are flared or rolled over to create a permanent attachment. \$\endgroup\$
    – Dave Tweed
    Commented Apr 26, 2019 at 22:30

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