Most likely solutions: These solutions work for IPEX as well as U.FL connectors.

1. Use U.FL retention clip to hold the U.FL connector on the jack.  
2. Use the U.FL press /pull tool (flat tip) during installation.
3. Use slightly longer U.FL cable assembly to allow more slack.

U.FL connector failure analysis & menu of fixes

Solutions for U.FL connector popping off the board jack during installation, assembly or handling. 

U.FL/MHF connectors are snap-fit, low-retention, low-profile parts designed for internal RF jumpers with very little side-load, few mate/unmate cycles, and strict cable routing. When process or layout violates those constraints, they disconnect.

Likely root causes (ranked by frequency)

1. Incomplete or misaligned mating
   • Plug isn’t fully “clicked” onto the jack (off-axis press, tweezers at an angle, or pressing on the cable not the ferrule).
   • Visuals: plug sits slightly high; no positive “click”; easy to flick off with light touch.
2. Wrong or mixed series
   • “U.FL-compatible” ≠ “identical.” Mixing I-PEX MHF variants (MHF4/MHF4L/MHF5) with Murata U.FL/Hirose W.FL jacks can reduce retention height/force. It may work electrically but is mechanically fragile.
3. Side-loading during downstream assembly
   • Short 55 mm lead + 1.37 mm coax stiffness puts peel torque on the joint when boards are placed into housings, rotated, or when nearby harnesses are tied down.
4. No local strain relief
   • Cable exits the plug and immediately bends; any touch, lid install, or tool bump pries the plug upward.
5. Board/jack issues
   • Jack not perfectly coplanar after reflow, solder voiding on the ground tabs, or board flex near the connector during screw-down causes micro-lift → easy disconnect.
6. Over-handling / cycling
   • These connectors are typically rated for ~10–30 cycles (series-dependent). Trial fits during debug quickly consume the rating and loosen the snap.

Immediate containment (no BOM change)

1. Mating process
   • Use the U.FL press /pull tool (flat tip) and press straight down on the plug body until a tactile click.
   • Add 100% visual check: the plug shoulder should sit flush with the jack; no gap.
   • Prohibit pressing on the cable or at an angle. Add a one-line work instruction with a photo.
2. Temporary retention
   • After mating, apply a retention clip.
   • Alternative: foam pad or tie-down that gently compresses the cable against the PCB or housing wall to neutralize peel.
3. Cable dressing
   • Add 5–10 mm of slack and route the first bend in the plane of the PCB (no upward bend within 10 mm of the jack).
   • If 55 mm is taut, test a 65–80 mm length to form a shallow loop.
4. Do not cycle
   • Lock the design; no trial mate/unmate on production units.

Short-term engineering improvements (low impact)

1. Strain-relief near the plug
   • Add a stick-on cable anchor (micro tie-base or tape) within 10–15 mm of the jack to redirect forces into the PCB, not the snap joint.
   • Consider a short heat-shrink boot (over the plug tail and first 8–10 mm of cable) to reduce sharp kinks (avoid covering the latch line).
2. Slightly softer cable
   • If mechanicals allow, 1.13 mm micro-coax is more flexible than 1.37 mm and reduces peel torque. Electrical loss increases slightly—verify link budget.
3. QC pull test (screen only)
   • After mating, use a light vertical tug test (e.g., 1–2 N) to confirm positive latch without risking damage. Do not do repeated full pull-offs.

Medium-term BOM / design changes (best reliability)

1. Match connector series 1:1
   • Confirm the exact jack series on the customer PCB (e.g., I-PEX MHF4 vs Murata U.FL-R-SMT). Provide plugs from the same series/brand with the correct mating height. Cross-brand “compatible” can work electrically but mechanical retention can be materially lower.
2. Higher-retention variant
   • Where available, migrate to I-PEX “MHF… with lock/retainer” hardware or a jack with a metal hold-down frame. Some series offer Secure-Lok/retainer clips that add a mechanical latch without changing RF geometry.
3. Connector relocation
   • Move the jack away from board edges / screw posts and add keep-out so fingers/tools can press straight down; add stiffener or support post under the jack area to limit board flex.
4. Right-angle choice
   • If the current jack is vertical and the cable must bend immediately, use a right-angle jack so the cable exits in-plane and doesn’t pry upward.

Checklist for diagnosis and solution

• Confirm series compatibility:  Find the jack manufacturer & series and use plugs from the matching series.
• Try longer sample lengths (by 1/4 inch to 1/2 inch or 10 mm) to find the minimum slack that stops pop-offs in your PCB assembly.
• Add near-connector heat-shrink boot and adhesive Kapton tabs.
• Add a retention clip on each connector.

Quick diagnostic checklist (5-minute triage)

1. Is the plug flush to the jack (no visible gap)?
2. Does it pop off when the cable is nudged sideways or when the housing is placed?
3. What is the jack brand/series on the PCB? (photo + BOM reference)
4. Is the first cable bend within 10 mm of the jack and upwards?
5. Is the board flexing near the jack during screw-down?

Answering those five will point directly to process vs. mechanical vs. component-match fix.

Bottom line

This is a mechanical retention problem typical of micro-RF snap connectors under side-load or mixed-series mating. Start with process correction + small strain relief + a bit more slack, and in parallel verify exact series compatibility. If the unit still sees bumps during assembly, add a retaining adhesive/tape or move to a higher-retention jack/retainer.