News Release from: Panasonic Electric Works UK
Edited by the Electronicstalk Editorial Team on 11 August 2004
Bellows technology improves connector reliability
The narrow pitch connector is probably one of the most overlooked components when considering the design and reliability of an application.
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The narrow pitch connector is probably one of the most overlooked components when considering the design and reliability of an application. This is not because it is the least important - paradoxically it is probably one component whose failure will have immediate effect on the correct functioning of the circuit. However it is certainly true that it is a component whose specification tends to be easily decided.
In reality, connectors are required to offer a long life in terms of reliable connection under the most arduous of conditions whilst being available at the lowest of prices.
In consideration of the nature of the technical requirements it must be recognised that they are not - unlike a relay or switch - single point connection devices.
Rather they are multipoint connections, maybe as many as 200-plus individual points that must be each 100% reliable in their own right to allow the complete connector to function correctly.
A failure of any single connection could well cause a complete circuit failure.
With the industry demands to decrease the narrow pitch connector sizes, especially on the board to board connector types the demands on the actual connection points has dramatically increased.
This is because the contact resistance and reliability is proportional to the contact area.
In a physically large connector this can be achieved with reasonable effort since the contact surface can be of a suitable size (as in the case of ISA or PCI type connectors).
However as the overall size decreases more design factors start to emerge in order to get the necessary contact pressure, contact angle and surface area.
With narrow pitch connectors now offering profiles heights of 1.5mm or lower and connector pitches of 0.4mm it can be seen that a new approach must be considered to design a product suitable for very low signals levels to be switched reliably.
In recognition of this need for high reliability, and the consequences of any type of contact failure, Matsushita has invested in development of the UBTS (unique bellows type structure) contact design.
The UBTS contact is a complex design specifically to ensure a high degree of reliability in the contact area.
In many lower quality connectors the contacts consist of little more than straight pins clamping into a Y-shaped housing.
This can lead to problems in contact contamination building up over a period of time or the point contact not offering 100% connection.
This may not cause problems at relatively high voltage levels where the contamination may be "punched through", above the 10V DC level for example; however it can certainly cause an apparent open circuit when much lower signal levels are present.
Another problem occurs in lower quality connectors when considering resistance to impact torsion.
This can be a major problem in portable applications (automotive, laptop computer or mobile phone applications for example).
Although this may not result in a permanent break in the connection it is possible that a temporary break can cause miss operation of the circuit or spurious signals to be generated to the detriment of other parts of the application.
The UBTS contact design uses a unique form on both sides of the contact.
On the socket side this consists of a six bend gold plated copper alloy contact with round corners being used on all the shaped areas.
Avoiding a sharp bends allows more reliability at the actual point of contact.
The gold plating is then added to a thickness of 0.2um.
A pinhole filling process further ensures that the gold plating completely covers the contact to avoid any problems that could occur by the existence of minute plating holes that are usually present in even the most tightly controlled manufacturing process.
The header by contrast uses a four-bend contact although this manufactured to the same process control as the socket.
The mating of the socket and header causes a compression (bellows) effect that forces the contact faces together ensuring a high contact pressure is maintained even under stressing or bending of the connector.
This compression effect also maintains a reliable connection under impact torsion effects as highlighted earlier.
Of course this UBTS technology can be applied to a wide range of connector product, not just the very high-density narrow pitch connectors.
In fact the bellows principle is used throughout the Matsushita connector range, even to the integrated connectors used in the connection of power and coaxial functions for mobile phones receptacle and plugs.
Used in this type of technology this allows in excess of 5000 reliable insertions and removals (equating to three operations per day for 5 years).
Although offering very high reliability levels the UBTS principles have been further improved on the most recent ranges of narrow pitch connectors.
A new V-notch principle has been tested and proven and is now being introduced to the current product ranges.
In principle a V-shaped notch portion is removed from the header side of the connector contact at the point of mating.
This avoids any possibility of contamination as the mating point is effectively isolated from the other areas of the connector.
Obviously the connector becomes even more impervious to the stresses of movement and bending as the V-notch principle effect increases the force required to allow the contact points to break.
Further the reliability is increased due to the chamfering nature of the V-notch so each single contact point can act as a bifurcated edge that is two individual points of contact.
In tests carried out by Matsushita involving making and breaking a socket and header pair in a polluted atmosphere it was shown that the V-notch contact had a far more stable contact resistance than the standard version.
Like many components the narrow pitch connector is constantly being evolved and improved whilst the market continues to demand lower costs and smaller packages.
The increasing use of board-to-board connectors, both floating and direct types, ensures that manufacturers will continue to invest time and effort into producing more efficient types of narrow pitch connectors to suit the electronics industry's requirements.
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