Molex SL Connector Complete Guide: Specs, Pinout, Applications & Selection (2.54mm Wire-to-Board)

The definitive technical reference for engineers selecting, specifying, and crimping Molex SL Series 70066 connectors — with full specs, mating part numbers, application guidance, and competitive comparison.

Introduction: Why Molex SL Remains the Gold Standard for 2.54mm Wire-to-Board Connections

When engineers talk about reliable, field-proven wire-to-board connectors at 2.54mm pitch, the Molex SL series consistently comes up — and for good reason. Introduced decades ago and still actively manufactured today (Status: Active, as of May 2026), the SL series has earned its place in industrial controls, consumer electronics, automotive accessories, and prototyping environments worldwide.

Unlike the JST PH (2.0mm) or JST XH (2.5mm) families that dominate the hobbyist and compact-device space, the Molex SL targets a slightly different sweet spot: maximum circuit density at 2.54mm pitch with a positive-latch retention mechanism, making it ideal for applications where accidental disconnection is unacceptable and where field serviceability matters.

This guide covers everything you need to know — from raw specifications and mating part numbers to selection logic, crimping best practices, and direct comparisons with competing connector families. If you need to identify your connector by pitch, see our connector pitch identification guide.

What Is the Molex SL Connector Series?

The Molex SL (Series 70066) is a single-row, crimp-style wire-to-board connector system operating at 2.54mm (0.100") pitch. It uses a positive-latch housing mechanism (Version G) that locks the receptacle housing onto the PCB header, preventing vibration-induced disconnection.

Key identity markers:

• Product Category: Connector Housings / Series: 70066
• Application: Signal, Wire-to-Board / Part: Receptacle
• Pitch: 2.54mm / Max Circuits: Up to 19 positions
• Rows: Single Row / Polarization: Yes
• Locking: Yes — positive latch, Version G

Full Technical Specifications: Molex SL Series 70066

General

Parameter	Value
Status	Active
Series	70066
Product Name	SL
Application	Signal, Wire-to-Board
Note	Version G
UPC	800753724785

Physical / Mechanical

Parameter	Value
Max Circuits	19
Pitch	2.54mm
Locking	Yes (Positive Latch)
Polarization	Yes
Panel Mount	No
Resin Color	Black
Resin Material	Polyester
Net Weight	1.530 g (19-circuit)

Environmental & Compliance

Parameter	Value
Operating Temperature	-40°C to +105°C
EU RoHS	Compliant per EU 2015/863
China RoHS	Compliant per SJ/T 11365-2006
REACH SVHC	Not Contained (Feb 2026)
Low-Halogen	Not per IEC 61249-2-21
UL	E29179
CSA	LR19980

Molex SL Series 70066 — Product Family Overview

Molex SL Series 70066: crimp housings (receptacles), vertical and right-angle PCB headers, and SL female crimp terminals (70058/71851) — all at 2.54mm pitch.

Mating Parts & Compatible Components

The complete Molex SL ecosystem: housings, vertical headers, right-angle headers, wire harness assemblies, and FFC cables — all at 2.54mm pitch.

PCB Headers (Mating Plugs) — Series 70066 Compatible

Description	Series
SL Single Row Housing Panel Mounts	70018
SL Single Row Crimp Housings	70107
SL Vertical Single Row Headers	70541 / 70543 / 70545
SL Vertical, Single Row, SMT Headers	74099
SL Right-Angle Single Row Headers	70551 / 70555
SL Right-Angle, Low Profile Headers	70553
SL Right-Angle, Low Profile, SMT Headers	70634

Header selection logic:

• Through-hole vertical (70541/70543/70545): Wave or hand solder. Best for prototyping and low-volume production.
• SMT vertical (74099): Reflow-compatible for automated SMT assembly lines.
• Right-angle TH (70551/70555): Wire harness exits parallel to PCB — common in enclosure-constrained designs.
• Right-angle low-profile SMT (70634): Most compact footprint for thin devices.
• Panel mount (70018): Front-panel or chassis-mount applications.

Crimp Terminals

Description	Part Number
SL Female Terminals (standard)	70058
SL Female Terminals (alternative)	71851

70058 and 71851 differ in wire gauge range and crimp barrel geometry. Consult PS-70058-001.pdf and PS-71851-001.pdf to match your wire AWG. Mismatching terminals to wire gauge is the single most common cause of field failures.

Molex SL vs. Competing 2.54mm Connector Families

Molex SL vs. JST XH (2.5mm)

Molex SL (2.54mm, black, positive latch) vs. JST XH (2.5mm, white, friction fit) — direct visual comparison for engineers choosing between these two dominant wire-to-board families.

Attribute	Molex SL	JST XH
Pitch	2.54mm	2.50mm
Max Circuits	19	16
Locking	Positive latch	Friction + tab
Operating Temp	-40°C to +105°C	-25°C to +85°C
SMT Header	Yes (74099, 70634)	Limited
Typical Use	Industrial, signal	Consumer, hobby

The Molex SL's +105°C ceiling vs. JST XH's +85°C makes it the preferred choice for industrial control panels and automotive accessories. See our JST XH complete guide for a full breakdown.

Molex SL vs. Molex KK 254 (2.54mm)

Molex SL Series 70066: housings from 2 to 19 positions, vertical and right-angle headers, and SL female crimp terminals (70058/71851) on carrier strip.

Both operate at 2.54mm pitch, but the KK 254 uses a different housing geometry and terminal system. The SL is preferred for higher circuit counts (up to 19 vs. KK's typical 12-position maximum) and offers more PCB header mounting styles including low-profile SMT.

Molex SL vs. DuPont 2.54mm (Generic)

Generic DuPont connectors use the same pitch but lack standardized locking, material specs, and compliance documentation. The Molex SL carries UL E29179, CSA LR19980, EU RoHS, and REACH SVHC clearance. See our common connector types guide.

Application Scenarios

1. Industrial Control Panels

-40°C to +105°C range and positive-latch retention make SL ideal for PLCs, motor drives, and sensor interfaces. Up to 19 circuits covers most I/O signal harness requirements.

2. Automotive Accessories & Aftermarket Electronics

CSA/UL certifications and temperature range suit non-safety-critical automotive wiring — dashboard electronics, lighting controllers, infotainment auxiliary connections.

3. Test & Measurement Equipment

Polarized locking prevents mis-connection during frequent connect/disconnect cycles in bench fixtures and ATE. STEP/SOLIDWORKS 3D models accelerate fixture design.

4. Medical Device Peripherals (Non-Life-Critical)

EU RoHS per EU 2015/863 and REACH SVHC clearance (Feb 2026) support Class I medical device peripherals and laboratory equipment.

5. Prototyping & Low-Volume Production

10 header variants let engineers select the optimal PCB footprint without changing the wire harness. Browse pre-crimped MX2.54 assemblies to skip crimping entirely.

Crimping Best Practices

• Wire gauge: Match to terminal spec (PS-70058-001.pdf or PS-71851-001.pdf). Wrong gauge = field failure.
• Crimp height: Within tolerance per spec. Use calibrated tool with correct die set.
• Insulation crimp: Both conductor barrel and strain relief must be fully formed.
• Terminal insertion: Push until positive latch clicks. Partial insertion = second most common failure cause.
• Extraction: Use correct extraction tool — never force or pry.

PCN History

PCN 510396 (2022-02-03): Packaging change only — delivery unit, packaging size, label, or material. No product changes. No re-qualification required for existing designs.

Frequently Asked Questions

What is the pitch of the Molex SL connector?

2.54mm (0.100") — same as standard 0.1" headers. See our pitch measurement guide if unsure.

How many circuits does the Molex SL support?

Up to 19 circuits, single row — positions 2 through 19.

What is the operating temperature range?

-40°C to +105°C — suitable for industrial and automotive accessory applications.

Is the Molex SL RoHS compliant?

Yes — EU RoHS per EU 2015/863 and China RoHS per SJ/T 11365-2006. REACH SVHC: Not Contained (Feb 2026 list).

What is the difference between terminal 70058 and 71851?

Both are SL Female Terminals for Series 70066, differing in wire gauge range and crimp barrel geometry. Consult PS-70058-001.pdf and PS-71851-001.pdf.

Can Molex SL use surface mount PCB headers?

Yes — Series 74099 (vertical SMT) and 70634 (right-angle low-profile SMT) are reflow-compatible.

Is Molex SL the same as a DuPont 2.54mm connector?

No. Molex SL has UL E29179, CSA LR19980, positive-latch retention, and full compliance docs. Generic DuPont has none of these.

What crimp terminals does Series 70066 use?

SL Female Terminals 70058 and 71851.

Is Molex SL low-halogen?

No — not per IEC 61249-2-21. For halogen-sensitive applications, consult Molex design services.

What PCB header for Molex SL receptacle?

Vertical TH: 70541/70543/70545 | Right-angle TH: 70551/70555 | SMT vertical: 74099 | SMT right-angle: 70634.

Where to buy Molex SL (MX2.54) cable assemblies?

Keszoox stocks pre-crimped MX2.54 assemblies — 2–12 pin, same-side/reverse-side/single-head, 22AWG UL1007, global shipping.

Selection Checklist

• Circuit count ≤ 19, single row ✓
• Pitch = 2.54mm ✓
• Operating temp within -40°C to +105°C ✓
• Signal-level application (not high-current power) ✓
• Positive-latch retention required ✓
• EU RoHS / China RoHS required ✓
• REACH SVHC clearance required ✓
• UL / CSA certification required ✓
• Low-Halogen NOT required ✓
• PCB header mounting style confirmed ✓
• Wire gauge matched to terminal (70058 or 71851) ✓

Conclusion

The Molex SL Series 70066 is one of the most mature, well-documented wire-to-board connector systems at 2.54mm pitch. Its positive-latch retention, -40°C to +105°C range, up to 19 circuits, 10 PCB header variants, and full EU/China RoHS + REACH compliance make it the technically correct answer where JST XH's 85°C ceiling or generic DuPont connectors fall short.