Micro coaxial termination in PTH structure and method.
Original Publication Date: 2002-Mar-14
Included in the Prior Art Database: 2003-Jun-12
The present invention discloses a Plated-through hole (PTH) structure which allows termination of mini coaxial cables directly into a printed circuit board PTH without a conventional coax termination connector. This allows high density coax cable connections into a circuit board, without the added cost and noise associated with the additional connection hardware. The invention can use either a semi conventional PTH, or a special PTH with a stepped configuration to accept a stripped, raw mini coaxial cable end which is conventionally soldered into the board. When the stepped hole structure is used the central signal wire is solder attached to the smaller diameter portion of the PTH barrel. The outer shielded cable portion is solder attached to the larger diameter portion of the PTH. The two PTH segments are electrically isolated at the step. When the semi conventional hole structure is used the middle signal conductor is soldered into the hole and the outer shield is soldered to a ground pad on the outside surface of the board. The invention allows very dense, low noise attachment of coaxial cables directly to high speed digital and telecom microwave circuit boards. The technique could even allow discrete wire connections for critical nets to be made between locations on the same board. A diagrammatic sketch of the stepped hole with a mini coax cable soldered in and a cross section drawing showing one cross section in which the stepped PTH coax termination hole can be constructed as shown below. Alternatively coax cables can be attached directly to the board by soldering the signal ends into a conventional PTH while the ground shield attached to a nearby grounded land, as shown below. The termination of the cable shield is accomplished by connection to a ring-shaped pad with connection to one or more PTHs that are drilled and plated to connect to the appropriate internal wiring layer. Co-axial to the ring-shaped pad is a connection for the cable's center lead, which is inserted into the plated hole. Both the shield and the center wire can be soldered into place.