How does height impact socket receptacle selection?

Many, many moons ago, as a young PCB designer, I remember my boss yelling at me to hurry up with my design. He kept barking “don’t worry about the connector, we’ll deal with it later, just put a ‘keep out’ area in that location and run the signals to dummy IO points.” There were so many more important things to consider: swapping gates, reducing packages, ECL stub lengths, differential-pair signal lengths, flashing thermals on the power planes. Yikes! I had enough to worry about, much less that stupid passive plastic device. It can wait.

Fast forward to now. Each day I try to help mechanical and electrical engineers undo the damage caused by not knowing and/or not planning for connectors. I wonder if any college engineering program even includes connector technology? I suspect most consider it somewhat less important than focusing on logic devices. So, from the standpoint of reducing product costs of PCB fabrication for through-hole devices, consider the following.

Short receptacle: If a customer is trying to design an ultra-low profile leaded device and has height limitations, explore tail-less, low-profile receptacles, as long as the pin spacing is generous enough to allow for easy trace routing. If the trace routing is limited by obstructions, then the user is looking at adding PCB layers, which is never good for the budget.

Short receptacles help ensure a low PCB profile. However, because they are embedded in the PCB, they do feature larger holes and offer less signal routing channels.

Another advantage of short receptacles is that they may be presented in a deep drawn tape pocket on tape and reel designs. However, if not presented on tape and reel or on another form of carrier, they must be individually placed.

Tall receptacle: If a customer is using a high-density, high-pin count leaded device such as a microPGA, then it should be suggested that he or she should consider a pin tail receptacle that will only require typically a via size hole. This will allow the customer to maximize routing channels between pins.

Tall receptacles feature a smaller diameter through the PCB tail, which allows for more signal routing channels. If they are equipped with a press-fit retention barb on the barrel, then they can be assembled in the insulator.

However, if taller than the PCB height, there may be dimensional interference. Additionally, tall pins and thin tails are susceptible to tilt.

Sometimes dismissing or ignoring the simple technology devices can bite back the hardest from your project budget.

Martin Houlroyd is Principal Engineer/Marketing Specialist at Preci-Dip. He has worked in the interconnect industry for 35 years. Email him at m.houlroyd@precidip.com.<