WO2012069928A1

WO2012069928A1 - Board connector assembly

Info

Publication number: WO2012069928A1
Application number: PCT/IB2011/003125
Authority: WO
Inventors: Gert Droesbeke; Ould Yahya
Original assignee: Fci
Priority date: 2010-11-24
Filing date: 2011-11-23
Publication date: 2012-05-31

Abstract

The present invention relates to a connector assembly comprising : a printed circuit board (PCB) having a through- hole; a connector mounted on a first surface of the PCB and having a mounting peg received in the through- hole. The connector assembly further comprises a locking member cooperating with the mounting peg thereby increasing the retention force of the peg in the through-hole.

Description

BOARD CONNECTOR ASSEMBLY

Field of the invention

The invention relates to a connector assembly comprising a printed circuit board (PCB) and a connector mounted thereon.

The invention also relates to a method for retaining a connector on a first surface of a printed circuit board.

Description of prior art

In Fig. 1 a connector system, such as used in a telecom cabinet, is shown comprising a cable connector 1 for a cable 2 attached to a front panel 3 having openings 4 for insertion of the cable connector 1. The connector system further comprises a printed circuit board (PCB) 5, located behind the front panel 3 and a board connector mounted on top of the PCB 5 to electrically connect the board connector electrical terminals (not shown) to the signal electrical tracks carried by the PCB.

The board connector comprises an electrical terminal assembly 7 and a shielding housing 8 which supports and partially surrounds the electrical terminal assembly 7. The PCB 5 also has pre-formed plated through-holes configured to receive the board connection ends of the board terminals and pre-formed holes 5' , 5' ' for locating the shielding cage 8.

Referring to Fig. 2, it is displayed a detailed bottom view of the board connector assembly shown in Fig. 1. The shielding housing 8 comprises a main body, having a U-shape cross-section, supporting the electrical terminal assembly 7 and a front portion having a square cross- section. The shielding housing 8 further comprises mounting pegs 17 for mounting the shielding housing 8 to the PCB 5.

The mounting pegs 17 are preferably pin-in-paste (PIP) or wave-solder pegs. In PIP process, first a paste is applied on the PCB 5 as in SMT . Subsequently the shielding cage 8 is placed on the PCB 5, such that the mounting tails 17 are positioned in plated-through holes 5' (see Fig. 1) of the PCB 5. Next re-flow is performed such that the paste fills the holes 5' around the inserted pegs 17 and acts as a solder agent for retaining the shielding cage 8 to the PCB 5.

Fig. 3 shows another example of a board connector which includes a housing, electrical terminals (not shown) born by modules and a shielding. The housing comprises, at its front portion, a mounting peg 38 which extends downwardly from the bottom wall of the housing.

The board connectors are generally mounted on the top surface of the PCB 5. However for higher density purpose, it becomes usual to mount board connectors on the opposite bottom surface of the PCB. The assembly for mounting board connectors to both major surfaces is the following:

1) mounting a first board connector on a first major surface of the PCB by locating the mounting peg(s) in the corresponding PCB receiving hole;

2) optionally passing the PCB with the first connector mounted thereon in a reflow chamber in order to secure the connector terminals in the PCB plated through- hole;

3) turning upside-down the PCB with its first connector so as the opposite second major surface becomes a top surface, and mounting a second connector to the second major surface by locating the mounting pegs in the corresponding receiving hole; ^■5

4) reflowing the whole PCB assembly in a reflow chamber to secure the connector terminals of either the second board connector or both first and second connectors when step 2) has not been performed yet.

During the above-described process it has been observed that the first connector, when the PCB is turned upside-down, comes off the PCB during the reflow step, under the action of the gravity force.

It is easily conceivable that this issue has to be overcome in order to maintain the connector assembling process profitable in terms of reliability, productivity and cost.

Summary of the invention

It is an object of the invention to provide an improved retention system for a connector mounted onto a printed circuit board and a method for improving retention of the board connector onto the PCB. Short description of the drawings

These and further aspects of the invention will be explained in greater detail by way of example and with reference to the accompanying drawings in which: Fig.l shows an example of a connector system comprising a board connector connected to printed circuit board and in which the board connector is further connected to a cable connector;

Fig.2 shows a perspective view of a prior art shielding cage;

Fig.3 shows a perspective view of another a prior art board connector; Fig.4a and 4b show a retention peg inserted through a through-hole of a printed circuit before and after having be submitted to a riveting transformation process;

Fig.5 shows a first embodiment of the retention assembly according to the invention;

Fig.6 shows a second embodiment of the retention assembly according to the invention;

Fig.7 shows a third embodiment of the retention assembly according to the invention;

Fig.8 shows a fourth embodiment of the retention assembly according to the invention;

Fig.9 shows a cross-sectional view of a silicon ring used in a fifth embodiment.

Fig.10 and 11 show a fifth embodiment of the retention assembly according to the invention in use.

The figures are not drawn to scale. Generally, identical components are denoted by the same reference numerals in the figures.

Detailed description of preferred embodiments

Fig. 4a and 4b disclose an example of processing a mounting peg so that it features an improved retention capability.

Fig. 4a shows a cross-sectional view of a mounting peg 10 (either metallic or plastic) inserted into a dedicated through-hole 11 of a PCB 12. The PCB comprises a top and a bottom surface, separated one from the other by a distance corresponding to the thickness of the PCB. The mounting peg has a length greater than the thickness of the PCB, so that a protruding portion 13 of the peg 11 extends beyond the bottom surface 20.

After the positioning of the peg, the protruding portion 13 is submitted to a mechanical deformation so as to provide a retention head 14. The formed retention head 14 should be configured to close off the through-hole 11 at the bottom surface 20 as shown in Fig 4b. Advantageously, the retention head 14 comprises portions which bear against the major surface around the through-hole.

The process for forming the retention head from the pin shape peg uses mechanical. However if the material of the peg displays a low deformability coefficient, a heating step of the protruding portion 13 is necessary in order to avoid breakage of the peg during the mechanical deformation. The purpose of the heating step is to soften the material so as it can withstand mechanical deformation without breaking. For instance, the heating step can be performed by ultrasonic vibration or laser.

Once the material is softened, a forward portion is swatted so as to provide the retention head. One of the advantages of the first embodiment is that there is no need to implement an additional component to effectively secure the peg in the through-hole.

Referring now to Fig. 5, it is disclosed a second embodiment for improving retention of the peg in the through-hole .

Fig. 5 is a cross-sectional view of a PCB 12 having two pre-formed through-holes 11 in which are inserted two mounting pegs 10. Each peg 10 comprises two arms 15, separated by recess 16 formed in the main body. The recess 16 emerges at the distal end of the peg.

Thanks to the presence of the recess 16, the arms 15 are able to flex inwardly during the insertion of the peg in the through-hole 11/ the mounting of the peg is therefore easy since a lower insertion force is required due to less friction of the peg with the inner wall of the PCB through-hole.

The retention system further comprises a locking member 17. The locking member 17 comprises a body 18, having a plate shape, from which extends locking lance 19. The locking lance 19 has a profile complementary to that one of the recess 16. Once the mounting peg 10 is in place in the through-hole 11, the locking member 17 is pushed against the bottom surface 20 of the PCB in such a way that the locking lance 19 is snap-fitted into the recess 16. The locking lance 19 is configured so that, when it is inserted in the recess 16, it spreads the arms 15 of the pegs which then interact against the inner side walls of the through- hole 11 to provide interference fitting.

According to a variant, the distal end of the arms is provided with a lateral wing (shown in dotted line in Fig. 5) which is arranged to snap against the edge of the through-hole at the bottom surface 20 of the PCB to increase locking efficiency.

The locking member 17 can be made of any material, in particular in plastic.

During the assembly, the first board connector is placed on the first surface (upper surface) of the PCB with a pick-and-place machine, then an insertion tool is applied to insert the peg and the board connector terminals in their respective through-hole and finally a tool is used to push the locking member 17 against the bottom surface of the PCB so that the locking lance of the locking member is snap-fitted in the recess 16 to secure the peg in the through-hole . Another example of the retention system is shown in Fig. 6. It comprises a PCB 12 with through-hole 11 arranged to receive a mounting peg 10 having a pin shape. When inserted in the through-hole 11, the portion of the peg protrudes from the bottom surface 20 of the PCB 12. The protruding portion 13 has a body having an arrow profile. In particular, it comprises a constricted zone 21, which ends by an enlarged retention head 22. The constricted zone 21 comprises a peripheral recess 23 which is located adjacent the bottom surface 20 when the peg 10 is inserted in the through-hole 11.

The retention system further includes, as in the previous embodiment, a locking member 17 for cooperating with the mounting peg. The locking member 17 has a main plate-like body, provided with at least one through-hole 24 configured to receive the protruding portion 13 of the peg 10. The thickness of the plate will be chosen to correspond substantially to the width of the peripheral recess 23 so as the locking member 17 is snap-fitted around the protruding portion 13. Preferably, the contour of both the peripheral recess 23 and the through-hole 24 of the locking member are angular to improve their interference fitting. Once the locking member 17 is in place, the distal retention head 22 of the peg locks behind the locking member 17 to ensure good retention.

Advantageously, as shown in Fig. 7, cut-outs 25 are formed around the through-hole 24 of the locking member in order to facilitate insertion of the peg 10 therein.

Turning now to Fig. 8, is shown a third embodiment of the retention assembly. Fig. 8 displays an enlarged cross- sectional view of the peg 10 inserted into the through-hole 11 of a PCB 12. As shown, the peg comprises a protruding portion 13 extending below the bottom surface 20 of the PCB 12. The retention assembly further includes a locking member 17 comprising a plate having a through-hole; the locking member can be seen as an eyelet. The plate further comprises a plurality of cut-outs formed around the hole and radially extending from the hole, so that the hole is surrounded by flexible tongues separated by the cut-outs.

In order to be effective as a retention member, the size (e.g. the diameter of the hole, if the hole is circular) of the through-hole is chosen to be slightly smaller than that one of the protruding portion 13 so that the protruding portion 13 of the peg is capable to press against the flexible tongues. In use, the flexible tongues are anchored to the protruding portion 13 as a harpoon. Thus when the PCB is turned upside-down, the retention of the peg is maintained thanks to the anchoring of the tongues 27 against the peg 10. The locking member can be made of either in plastic or preferably in metal

Now it will be described two variants of the method to implement the retention assembly of the third embodiment.

According to the first variant:

The locking member 17 is first fixed to the bottom surface 20 of the PCB (e.g. by gluing or welding) so that the center of the through-hole 24 of the locking member 17 lies coaxially with the center of the PCB through-hole 11. In this fixed position, the locking tongues of the locking member are in a non deformed state, i.e. they are cop l anar and extend substantially parallel to the bottom surface 20 of the PCB.

In a second step, the board connector is mounted on the top surface 20 of the PCB 12 with its mounting peg 10 penetrating into the through-hole 11. During the insertion, since the outer dimension of the peg is higher that the size of the through-hole 24 of the locking member, the protruding portion deforms the flexible tongues by spreading them apart. When the peg reaches its final position, the sharp edge of the flexible tongues spears into the body of the peg to provide the locking.

According to the second variant:

The board connector is first mounted on the top surface of the PCB with its mounting peg 10 penetrating into the through-hole 11.

In a second step, the locking member is applied against the bottom surface of the PCB so that the protruding portion 13 of the peg penetrates the through- hole 24 of the locking member. Due to the fact, the outer dimension of the peg is higher that the size of the through-hole 24 of the locking member, the protruding portion deforms the flexible tongues by spreading them apart; in the final position the sharp edge of the tongues bit the body so as to ensure the anchoring of the tongues.

Fig. 9 shows a cross-sectional view of a silicon seal 28 used as a locking member in a fifth embodiment of a retention assembly. The silicon seal 28 has the shape of a sleeve comprising a circular main body 29 and a hole 30 formed therein. The silicon seal 28 is configured to receive a locating peg 10 of a connector through its hole 30.

As seen in Fig. 10, for the silicon seal 28 further comprises a peripheral groove 31 sized to receive the peripheral edge of the through-hole 11 of the PCB 12 so as to ensure a primary locking of the seal 28 around the through-hole 11.

Preferably the diameter of the seal hole 30 is chosen slightly larger that the greatest outer dimension of the peg to ease the insertion of the peg 10 in the seal 28 with limited risk of removing the latter during the insertion of the peg.

The fifth embodiment makes use of the thermal expansion property of the silicon material in order to improve the retention of the peg in the PCB. The thermal expansion relates to the tendency of matter to change in volume in response to a change in temperature. For instance silicon has a coefficient of thermal expansion three times higher than that of the plastic material used in the PCB.

Now, in reference with Fig. 10 and 11, it is explained the method for improving the retention of the peg .

In a first step the peg is put in place in the through-hole 11 of the PCB 12 which already has received a silicon seal 28 fitted in the through-hole 11.

The assembly is then subjected to a heating process, for instance it is a reflow process at a temperature ranging from 260 to 265°C, for thirty seconds. During the reflow, the silicon expands so as to occupy the void present between the peg 10, the PCB and the silicon seal 28. As a consequence the silicon exerts pressure on the peg and the PCB, which imparts higher retention force on the peg .

Alternatively, the silicon seal 28 is pre-mounted around the peg 10 and then the peg with its seal is inserted into the through-hole 11 of the PCB.

It should be noted that the present invention can be implemented with any material currently used to form the board connector peg namely, in plastic or in metal or metal alloy.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. The invention resides in each and every novel characteristic feature and each and every combination of characteristic features. Reference numerals in the claims do not limit their protective scope. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements other than those stated. Use of the article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The present invention has been described in terms of specific embodiments, which are illustrative of the invention and not to be construed as limiting.

Claims

1. Connector assembly comprising:

- a printed circuit board (PCB) having a through- hole;

- a connector mounted on a first surface of the PCB and having a mounting peg received in the through- hole,

characterized in that the connector assembly further comprises a locking member cooperating with the mounting peg thereby increasing the retention force of the peg in the through-hole.

2. Method for retaining a connector having a mounting peg on a first surface of a printed circuit board having a through-hole adapted to receive the mounting peg, comprising the steps of:

- mounting the connector on the first surface of the PCB so that the mounting peg is received in the through-hole and a portion of the mounting peg protrudes beyond a second surface opposite the first surface ;

- mechanically deforming the protruding portion of the peg to form a retention head configured to close the through-hole at the second surface.

3. Method for for retaining a connector having a mounting peg on a first surface of a printed circuit board having a through-hole adapted to receive the mounting peg, comprising the steps of:

- providing a thermally expandable sleeve element either around the mounting peg or the through-hole

- inserting the mounting peg into the through-hole - performing a thermal treatment such that the thermally expandable sleeve element exerts a pressure on the peg and the through-hole.