Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – Distinct contact secured to panel circuit
Patent
1996-06-27
1998-11-10
Abrams, Neil
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
Distinct contact secured to panel circuit
324 725, 439888, H01R 909
Patent
active
058334793
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/FI 95/00497, filed Sep. 13, 1995.
BACKGROUND OF THE INVENTION
The invention relates to a test point enabling hands-free diagnostic testing of electronical circuits. Printed circuit boards (PCB) as well as other electronical circuits need to be tested and adjusted. In order to facilitate such testing it is known to use test points which allow the test engineers to work "hands free" while setting and adjusting the test equipment. The test points allow the test engineer to attach hook type test probes and log results without having to hold the test probes, used for this purpose.
The test points used today for this purpose are in the form of a loop which is soldered to the PCB with one or two copper pad pieces on the PCB to be tested. Typically, the loop-type test points require a hole through the PCB (which may be plated through), and there must be at least one pad on the underside of the PCB, which takes board space on the underside of the PCB, which is not required with surface mount technology. A pad is required on both the upperside and the underside of the PCB linked with a plated through hole, if the signal to be tested is on the upper side of the board. The loop-type test point has to be hand-fitted and is often hand-soldered, which makes it expensive and difficult to justify.
SUMMARY OF THE INVENTION
The object of the present invention is to eliminate the above problems. To achieve this, the test point of the invention it comprises a body with two planar, at least essentially parallel end surfaces which are spaced apart and face opposite directions, the end surfaces being connected to each other by a waist portion which is in electrical contact with at least one of the end surfaces. The diameter of the waist portion is smaller than the diameter of the end portions: the diameter of the waist portion is chosen to fit in the hooks of common type test probes. The body is preferably symmetrical and made in one piece of a conducting metal such as brass or copper, the diameter of the end surfaces being somewhat larger than the height of the body. This makes the test point suitable for use in a surface mount device (SMD) machine of standard type. In this case, the test points are placed in a surface mount device (SMD) tape of standard type. The present invention also concerns a surface mount device (SMD) tape provided with test points according to the present invention.
The most important advantage of the present surface mount test point are that it is very easy to mount on printed circuit boards, it is suitable for machine mounting in solder paste which has been applied to the test point pad and can be soldered in a reflow oven. A copper surface of approximately ten square millimeters suffices to function as a mounting base for the test point. The test point can be supplied in a standard 8 mm wide surface mount device tape and can thus be reel mounted. The flat end surfaces of the test point according to the invention allow the test point to be picked up with standard vacuum nozzles. When the diameter of the end portions is larger than the distance between them, the test point is stable and keeps an upright position, which makes it more reliable to fit. A symmetric test point is preferred, because symmetry makes the test point non handed and subsequently easier to mount in the tape and place on the PCB.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention will be illustrated by means of one preferred embodiment with reference to the attached drawing, in which:
FIG. 1 shows a commonly used loop-type test point mounted on a printed circuit board and seen from the side,
FIG. 2 shows the test point of FIG. 1 seen from above,
FIG. 3 shows the test point according to the present invention seen from the side,
FIG. 4 is a sectional view along the line IV--IV of FIG. 3, and
FIGS. 5 and 6 show a surface mount device tape with test points according to FIG. 3 placed in the pockets thereof.
DETAILED DESCRIPTION
FIG. 1 shows a known
REFERENCES:
patent: 3044151 (1962-07-01), Coler
patent: 3061760 (1962-10-01), Ezzo
patent: 3329851 (1967-07-01), Braeutigam et al.
patent: 5446393 (1995-08-01), Schaefer
Unknown author: "Testen von Hybriden und SMD-Schaltungen", Funkschau, No.12, Jun. 1988, pp. 57-58.
Stadler: "Viktigt att konstruera for provning", Elteknik Med Artuell Elektronik, No. 8, Apr. 1988, pp. 59-60, especially portion Konstruera for provning pa kortet.
Lyman et al: "Surface mounting provokes test challenges; integrating CAD and testing cuts production costs", Electrons Week, vol. 57, No. 25, Oct. 1984, pp. 50-53, especially portion Fixtures and probes (p.51).
Abrams Neil
Nokia Telecommunications Oy
Patel T. C.
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