Choosing a connector: guidelines on pitch and size

If you’re designing a cable assembly to carry signal or power in your product, you’ll need to select a connector to mate your conductors to your printed circuit board (PCB) or elsewhere in your product. And there’s a lot you’ll need to consider, from voltage rating to a variety of physical characteristics.

Two such characteristics are connector size and pitch. A connector’s pitch and size can put extra pressure on a cable assembly’s manufacturing process, increasing cost or reducing the cable’s effectiveness.

Specify connector pitch and size thoughtfully, and you’ll design an efficient and effective cable assembly. This article shows you how.

How connector pitch impacts production cost

In any connector containing multiple terminal pins, pitch is the distance from the center of one pin to the center of the next. Connectors with multiple rows of pins usually have the same pitch between rows as they do between pins, but in some cases the distance between rows is different.

When choosing a connector, use these two rules of thumb:

The smaller the pitch, the harder to manufacture

Why should a difference of half a millimeter matter when it comes to manufacturability?

It turns out, that extra space is precious. Manufacturing becomes more involved as connector pitch decreases, contributing to higher labor costs.

Here’s why:

When we’re building custom cables at high volumes, we use a cut, strip, terminate (CST) machine. The machine draws wire from a spool with a cast in it. Even though the CST machine contains wire straightening equipment, wire will still have some bend when it reaches the terminal. If the wire doesn’t rest in the terminal seat properly, the connection will fail. The smaller the connector pitch, the smaller that connector seat which needs to hold the wire.

This greatly increases the risk of connection failure.

To combat this, humans must closely monitor what is otherwise an automated manufacturing process. We have to slow our CST machines down, giving operators time to effectively monitor crimp quality and improving success rates. But this slowdown comes at a cost that adds up over thousands of connections.

You can think of connector pitch like a tolerance. As it gets tighter, production becomes slower and more expensive. If you’re working with a supplier who’s less careful about product quality, a little extra space could help shore up against quality issues.

Common pitches and standard connectors

You should specify standard components and connectors when possible. This will strengthen your supply chain and result in a more easily manufacturable product. A 2.54 mm (.100 in.) pitch is ubiquitous and gives cable assemblers plenty of space to produce good connections quickly.

We understand that sometimes a standard part won’t cut it. But the table below notes common connector series at each of the most common pitches. Sticking to these connectors will help you avoid excess tooling costs and supply shortages.

Pitch in millimeters	Pitch in inches	Common connector series
1.25 mm	0.049 in.	Molex PicoClasp, Molex PicoBlade
2.00 mm	0.0790 in.	JST PH, Molex Milli-Grid
2.54 mm	0.1000 in.	Molex KK 254, AMPMODU Mod IV and V, Molex C-Grid
3.00 mm	0.1180 in.	Molex Micro-Fit

How the right connector size leads to a more durable and affordable cable assembly

While the primary factors that determine connector size are the number of terminal pins and the pitch between them, two connectors that achieve the same result for your product can take up different amounts of space on your board.

In general, it’s best to use a larger connector when the space is available. Larger connectors are easier to manufacture, which helps your supplier provide a consistent cable and helps you save on labor costs in the long run.

If you sell equipment that will require regular maintenance, larger connectors will prove easier for service techs to unplug and reconnect. Smaller connectors are more likely to incur damage during handling and maintenance.

The design stage is the perfect time to consider connector size and pitch. The differences may seem small, but minor adjustments for the sake of manufacturability can make your design more reliable and much cheaper to produce.

Still have questions?

There’s more to connector specification than pitch and size. If you’re looking for more information to help you choose a connector for your cable design, check out our video explaining the different connector types or our guide to mating force and connector IP ratings.

If you want to talk to an expert about the manufacturability of your design, reach out. An engineer will get in touch to talk about your application.