PCB mounted connectors

Technics

Assembly and functional description

There are three methods of mounting a connector onto a printed circuit board. Two require soldering techniques, the other is solder free.

1) Throughhole technology:
The printed circuit board is manufactured with plated through holes for placement of the components. Once installed, the component can be soldered into position using either manual-, wave- or reflow-soldering techniques.

Small connectors (e.g. MMCX, MCX, SMB) can be packaged on tape and reel for placement by standard SMD-pick and place machines.

Advantages:

High mechanical stress
Standard pcb usage
Standard connector usage

2) Surface mounted:
Known as SMD (Surface Mount Device) or SMT (Surface Mount Technology). Before the components are placed, solderpaste is applied to the PCB pads. The board is then passed through a reflow solder oven.

Advantages:

Placement by standard SMD-pick and place machines
No "radiation" produced by protruding contacts
High packing density on the PCB

3) Press-fit technology:
Connectors are mostly soldered onto printed circuit boards. Soldering however, has several disadvantages as this process creates thermal stress, requires solder to be applied and costly manufacturing installations.
The Press-fit process, a technology that is increasingly becoming accepted for good reasons, is an alternative to soldering. The Press-in parameters comply with the IEC 352 standard.

Press-fit pins and PCB's
The Press-fit connector pins can have different shapes. They consist of a spring core and are tin plated for better contact performance. IMS Connector Systems prefers the eye of the needle shape (see illustration).
The drill holes in the PCB base material are metallised with a copper and a tin layer.

Assembly principle
The connector's Press-fit pins are pressed into the plated through-holes of the PCB by applying mechanical force. When being pressed in, the Press-fit pins are deformed. This creates a lasting gas-tight connection between the Press-in pin and the metallised drill hole. The elastic Press-fit pins ensure the mechanical stability and the electrical contact.

Advantages over soldering technologies
Compared with different soldering methods, the Press-fit technology offers the following advantages:

No soldering process
Simple and quick mounting
Damaged components can be replaced easily
No thermal stress
Environmentally friendly
Very good electrical performance
High mechanical stability

Assembly
No costly manufacturing facilities are required for mounting Press-fit connectors. The connectors are placed onto the PCB and pressed in with a defined force (see illustration). This can be processed automatically or manually.

Before Press-in

Press-in procedure

Top view

Bottom view

Replacing connectors
The spring core Press-fit shape enables multiple insertions to be made if necessary. Unlike soldering methods, this technology neither causes thermal stress nor contamination by solder.

Specifications

Mechanical specification
Applies to standard	IEC 352
Max. press-in force per Press-fit pin	180 N
Min. extraction force per Press-fit pin	20 N
Press-fit pin Press-fit material Press-fit surface Press-fit shape	Bronze SnPb over Ni Lead free Eye of the needle
Printed circuit board Base material Thickness Finish metallised drill hole	FR4 or equivalent 1,5 - 3,2 mm Ø 1 mm +0,09/-0,06
Environmental specification
Vibration	IEC 512 - 4
Long time storage	IEC 512 - 5
Operating temperature	-40° C up to + 85° C IEC 512 - 6
Climatic sequences	IEC 512 - 6
Corrosion (industry, atmosphere)	IEC 68 - 2 - 60 (method 4)

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