PC/104 and PC/104-Plus

Simply stack it - with ept press-fit technology

PC/104 is a standard for PC-compatible modules which are intermateable to set up a complete computing system.

The PC/104 ensures complete hardware and software compatibility, is extremely compact (96 mm x 90 mm), and comes with a standardized PC/104 Bus (ISA). Due to this standardisation, different PC/104 cards can be combined to implement a defined task.

Although PC/104 modules have been manufactured since 1987, a formal specification was not published until 1992, when the PC/100 Embedded Consortium designed the first release of a mechanical and electrical specification of a connector that fully supported an 8bit/16/bit ISA bus. Since then, interest in PC/104 has skyrocketed, with over a hundred different PC/104 modules introduced by numerous manufacturers.

Many different boards are offered based on PC/104 including:

• Complete single-board computers
• I/O boards for digital or analog I/O
• Boards for CAN, Profibus, LON,Ethernet
• PCMCIA boards

Since more powerful components are available, the PC/104 systems had to be supplemented with a faster bus system. The PC/104 system was supplemented with the PCI bus and thus it was further developed. This supplement is described in the PC/104-Plus specification. The older standard PC/104 bus uses the PC/XT, and PCAT card specification (IEEE P996). PC/104-Plus allows the addition of the PCI bus onto the card. The PC/104-Plus adds another connector to accommodate the PCI signals. In other words a PC104 card is just like the old Personal Computer PC-XT interface card, or PC-AT interface card, and the PC104-Plus board is just like an older mother board with ISA slots and PCI slots. This latter standard is widely used for embedded computing application

While the PC/104 bus comprises two connectors with 40 and 64 pins which can be placed side-by-side and a grid size of 2.54 mm, the PC/104-Plus features 120 pins with a distance of 2.00 mm. By using connectors with long press-fit pins, several boards can be stacked on top of each other. The clearances specified by the PC/104 consortium are ensured by using spacers and shrouds. The additional use of spacing bolts is therefore not required.

Historically, all long tail PC/104 connectors required a through hole solder application. While many through hole components may be hand or wave soldered, this is extremely difficult and time-consuming for the 104 gold-plated connector pins. Solder pre-form donuts or solder and flux bearing clips allow for improvements in the soldering process by eliminating the hand soldering operation; they do, however, still require a high temperature IR or hand solder process and close visual inspection.

The superior option for applying a long tail stack-through connector is with compliant pin technology. Adopted by the telecom industry many years ago, press fit technology has proven itself to be a cost-effective alternative to soldering connectors to a board. The compliant pins on the connector are designed to deform during the "press-in" process, resulting in an extremely tight and reliable connection to the PCB. Extensive laboratory testing and years of field operation have proven press fit connector reliability in demanding environments. Pressfit connector technology using compliant press-in zones on every pin has revolutionized the way PCB manufacturers mate connectors to PCBs of all kinds. It is the simplicity of applying the connector to the board, and the superior mechanical holding ability, which makes pressfit connectors a cost effective replacement for soldering.

The pressfit advantage:

* Proven reliability in environmental testing where temperature changes, shock, and vibration weaken solder joints

* Constant and defined impedance across all positions (excellent high frequency properties)

* Compensation for plated through hole irregularities

* No thermal stresses on the PCB

* No chance of fumes, gases, flux residue or solvents penetrating the solder joint

* No risk of cold solder joints

* No risk of shorts as a result of solder bridging

* No risk of solder interference on long tail connectors

* Fast and reliable application of the connector to the board with simple, flat rock insertion tools

* Serviceable and replaceable single contacts and whole connectors

PC/104 connectors are now available in pressfit versions in long and short tail. This allows for fast and simple insertion of the connectors into the finished boards, without any risk of uneven solder flow or contamination to the gold tails of the connectors.

Fast and simple insertion of the connector into the through hole is accomplished by means of a flat rock tool and a simple bottom support fixture mounted on a hand press. The entire press-in process takes less then five seconds, with all positions maintaining equal resistance across the hole. Another added benefit of pressfit connectors is the ability to rework the board by pressing the connector in a reverse process, allowing a replacement connector to be inserted. The innovative 'ept' PC 104+ pressfit-style connector is a revolutionary concept in the PC/104 market.

'ept' now offers the VarPol-PC/104 female connector in FlatRock press-fit construction. This connector was developed for the stacking of PCBs (Piggyback, Sandwich) and is particularly well suited for use in PC/104 modules. These connectors are available in the J1 and J2 variation with 2x32 and 2x20 pins. They can be obtained with short or long pins according to the PC/104 standard. VarPol connectors offer a wide range of possibilities for embedded PCB connection solutions.