I look at a lot of connectors every day. As a quality compliance manager, I review every cable assembly before it reaches a customer—roughly 200 unique items a year. And if there's one recurring issue that costs people time and money, it's bad crimps. Not bad connectors, not bad cable, but bad crimping technique.
If you've ever had a connection fail on a test board or seen intermittent issues in a prototype, this checklist is for you. It's a 3-step process I've used to spot and fix problems before they leave the bench. I'm not gonna pretend it's comprehensive, but it covers the mistakes I see most often.
Who This is For (and When to Use It)
This checklist is for design engineers, technicians, or procurement specialists who are personally assembling or verifying a Samtec cable assembly—either for a quick prototype or a small production run. Maybe you're testing a new design using a Samtec TSW header or a QSH series connector, and you just need to get one or two cables right.
I get it. When you're on a tight deadline, you just want to get it done. But I've seen too many projects get delayed because a $2 connector wrecked a $20,000 prototype. (Should mention: this was literally in our Q1 2024 quality audit—one bad crimp on a single cable assembly took out an entire test fixture.)
So, here are the steps. There are three of them. Follow them in order, and you'll catch the most common issues.
Step 1: Verify the Wire and Connector Match
This sounds obvious, but it's the most common mistake I see. You'd think a 24 AWG wire would work in a 24 AWG crimp barrel, but the insulation diameter is the real killer.
I once had a vendor claim our spec was wrong because their crimp looked fine. But when I measured the insulation, it was 0.065 inches—just slightly over the 0.060-inch max for that Samtec contact. The insulation wasn't fully seated, and the wire pulled right out. The vendor said it was 'within industry standard,' but the spec sheet from Samtec was clear. We rejected the batch. They redid it at their cost. Now every contract I write includes a note about checking insulation OD against the contact's spec.
Here's the checklist for this step:
- Check the wire gauge (e.g., 24 AWG, 26 AWG, 30 AWG) against the connector's datasheet. Samtec often lists compatible wire sizes on their website or in the drawings.
- Measure the insulation outside diameter (OD) with a caliper. Compare it to the max recommended OD for that specific contact part number.
- Don't assume 'standard' wire works. Wire from different manufacturers can have slightly thicker insulation. I've seen differences of 0.005 inches that caused crimping issues.
If you're mixing different wire types in one assembly, check each one. Mixing 24 AWG and 26 AWG wire in the same connector? You need to verify both against the contact's range. The most frustrating part of this step: you'd think a simple check would be automatic, but I still see it missed in 10% of the first-article inspections I do.
Step 2: Use the Correct Tooling and Die Set
This is where I see the most expensive mistakes. People use a generic ratcheting crimp tool with a random die. Or worse, they use a pliers-style tool 'just for this one cable.'
Looking back, I should have been more aggressive about enforcing tooling requirements earlier in my career. At the time, I thought 'any crimp tool that works for the wire gauge' was enough. It wasn't.
For Samtec connectors, the correct approach is:
- Use the manufacturer's recommended tool. For many of their discrete wire contacts (like for the TSW or MMSD series), Samtec specifies a specific hand tool or die set. Check their website or contact their engineering support—they publish this info.
- If you're using a third-party tool (like Daniels Manufacturing or Molex), verify the die profile matches the Samtec contact. Don't assume 'it looks close enough.' A die that's too wide for the contact won't create the proper crimp height, and a die that's too narrow will damage the contact.
- Check the crimp height. This is a number (in inches or millimeters) specified by the contact manufacturer. You can measure it with a micrometer after crimping. It's a direct indicator of whether the die is set correctly. If the height is off by more than 0.002 inches, the crimp is out of spec.
I ran a blind test last year with our production team: same wire and connector, but we used our proper tool with a verified die vs. a cheap generic tool. The cheap tool produced a visibly acceptable crimp, but when we measured pull-out force, the generic tool's crimps failed at 15 pounds. Our spec was 25 pounds. The generic tool was off by 40%. If I could redo that decision, I'd have invested in the right tooling sooner. But given what I knew then, I assumed all tools were roughly equivalent. They're not.
Step 3: Perform a Pull Test (or At Least a Visual & Physical Check)
This is the step most people skip. They crimp the wire, give it a gentle tug, and call it done. But a gentle tug doesn't simulate the forces a wire will see in a harness or during installation.
Dodged a bullet on a 50-cable run a few months ago: I insisted on a pull test for the first article, even though the technician said 'it's just simple crimps.' Turned out the crimp height was fine, but the insulation crimp wasn't fully closed. The wire would have worked for a few cycles, then failed under vibration. We caught it because we pulled—and the wire came out at 12 pounds, well under spec. Reworked the die setup and the next sample passed at 28 pounds.
Here's what to do:
- Use a pull tester if you have one. Most Samtec discrete wire contacts have a specified minimum pull-out force (e.g., 25 pounds for a 24 AWG wire). Set the tester to pull at a specified rate (usually around 1 inch per minute). The wire shouldn't separate before hitting the minimum force.
- If you don't have a pull tester, do a focused visual and physical check:
- Look at the insulation crimp: it should fully envelope the wire insulation without cutting into it. You should see no exposed wire inside the insulation barrel or outside it (where it exits the connector).
- Look at the conductor crimp: it should be symmetrical and centered. If it's off to one side, the die wasn't aligned.
- Give the wire a firm, steady pull—not a jerk—to see if there's any play. If you feel movement, it's a bad crimp.
At least, that's been my experience with Samtec's high-density connectors like the ERF8 series. The tolerances are tighter, and the consequence of a bad crimp is higher. If you're working with a larger pitch connector like a .100-inch MMSD, the pull-out forces might be slightly higher, but the principle is the same.
What to Avoid: Common Mistakes I Still See
I've been doing this for over 4 years, and I still catch myself making assumptions. Here are the pitfalls:
- Don't skip the pull test. I know it takes time. I know you're in a hurry. But one bad crimp on a critical signal can take hours to debug, not to mention the cost of rework.
- Don't use mismatched wire and contact. Even if it fits, check the insulation OD. That's the most common hidden issue.
- Don't trust 'experience' over the spec sheet. I once had a senior technician tell me 'we've always done it this way' when I asked about their tooling. Their pull test was failing. When I pulled up the Samtec spec sheet, we found we'd been using the wrong die for 6 months. They'd been compensating by squeezing harder, which damaged the contact.
- Don't assume a visual check is enough. A bad crimp can look perfect. And a good crimp can look slightly off. Only measurement—crimp height, pull force—tells the real story.
To be fair, not every project needs a full pull test on every wire. If you're prototyping with a Samtec TSW header and a short cable, a careful visual and physical check is probably fine. But for anything that goes into a product, or even a test fixture that sees multiple uses, I'd recommend at least sampling a few crimps from each batch.
That said, if you follow these three steps—matching the wire to the contact, using the correct tooling, and verifying with a pull test—you'll catch the problems that show up in my quality audits. The ones that cost time, money, and sometimes a weekend. And that's the whole point.