JAE Expands the MX77 Series of Compact, Low-Profile Connectors for Automotive ECUs

July 27, 2026

JAE has expanded its MX77 Series of compact, low-profile board-to-cable connectors—designed to interconnect automotive ECUs, BMS (Battery Management Systems) and other in-vehicle devices—with two new additions now in mass production: a single-row mid-mount *MX77B and the all-SMT mounting MX77C.

Overview

In recent years, as automobiles have become more sophisticated and electrified, the number of in-vehicle electronic devices—such as ADAS sensors and various ECUs—has increased. Consequently, there is a growing need for smaller and lower-profile ECUs and connectors to make effective use of the limited space inside vehicles.
To address these needs, we developed the MX77A automotive board-to-cable connector and added the MX77D—which features a lower profile on the socket side—to our lineup, supplying these products to automotive manufacturers and Tier 1 suppliers both in Japan and overseas.
The newly released MX77B, adopts a single-row mid-mount structure to achieve a height reduction of approximately 30% compared to the MX77A, achieving a 6.6 mm mounting height for the pin header, and a mated height of 6.72mm. This makes it well suited to next-generation ECU’s and BMS units where device thickness must be minimzed.
The MX77C, an onboard type with an all-SMT termination design. Both the contacts and hold downs are SMT, allowing the revers side of PCB to be used for other components. Importantly, the MX77C mates with the existing MX77A ensuring compatibility with existing designs.
Together with the existing MX77A and MX77D models, this series addresses a wide range of mounting needs and contributes to the miniaturization and high-density mounting of automotive ECUs, battery monitoring systems, and other devices.

*Mid-mount type: A method in which the PCB is cut to allow for SMT mounting of the connector. This allows the connector height to be incorporated within the PCB, making it effective for reducing the overall thickness of the device.

MX77A Series: https://www.jae.com/en/topics/detail/id=1730
MX77D Series: https://www.jae.com/en/topics/detail/id=96413

Features

MX77B/MX77C：

• Ultra-compact connector with a terminal size of 0.4 mm (pin width)
• ISO Thin Wall 0.35 sq wires are compatible with all cavities
• Tested to various automotive specifications

MX77B：

• Mid-mount pin header with a height of 6.6 mm above the PCB after mounting (6.72 mm when mated). The mating socket connector has a height of 9.1 mm
• Reverse-mating type where the position of the lock lever latch is opposite to that of the MX77A, MX77C, and MX77D

MX77C：

• It mates with the existing MX77A socket connector
• Uses the same socket terminals as the existing MX77A; features a box-type terminal design resistant to external loads

MX77B Mating Height

MX77 Series Mating Comparison

Applicable Markets

Various automotive body ECUs, automotive battery system equipment, BMS (Battery Management System), etc.

General Specifications

*The 8 position MX77C only has 2 positions populated.

Materials and Finishes

Appearance

MX77B

Socket Connector		Angled Pin Header
Socket Housing	Socket Terminal

MX77C

Angled Pin Header

Reference

MX77 Series (For more details)opens in a new window

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Information and details given here are as of the date of publication.
Please note that the details may be changed.