Abstract:
A subject of the present invention is to provide a clip-type lead frame having flexibility against a board thickness variation caused by not only an uneven product quality but also several different thick type products. To this end, the provided clip-type lead frame has a height adjustable means at lead pins corresponding to upper or/and lower side connection pads of the semiconductor device or the sub-board.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a clip-type lead frame and an electric device with two substrates electrically connected by the lead frame. 
     BACKGROUND OF THE INVENTION 
     Conventionally, there have been proposed a number of clip-type lead frames for electrically connecting a main substrate with a sub-substrate or semiconductor device provided on the main substrate. For this purpose, each of the proposed clip-type lead frames has pairs of clip-type lead pins. The paired lead pins are so sized and shaped that they clip and hold the sub-substrate or semiconductor device and, simultaneously, make contacts with corresponding connection pads, if any, provided on a periphery of the sub-substrate or semiconductor device. 
     For example, a variety of clip-type lead frames have been proposed in Japanese Patent Laid-open Publication Nos. 7-320801, 7-230837, 9-83132 and 5-101854 and Japanese Utility Model Laid-open Publication Nos. 2-8877 and 2-88248. Typically, each of the lead frames proposed in the applications has a specific structure similar to that described in FIG.  9 . 
     Referring to FIG. 9, a memory board  100  or sub-substrate mounted on a main-substrate  200  by means of clip-type lead frames  110  and  120  of the same size and structures. For clarity, electric wires provided on the main-substrate  200  are omitted from the drawing. The memory pad  100  supports connection pads  102 ,  104  and  106  on a peripheral portion of its upper surface and another connection pads  101 ,  103 ,  105  and  107  on the opposite peripheral portion of its lower surface at regular intervals. 
     As can be seen from the drawing, the clip-type lead frame  110  or  120  has lead pins  121 - 127  corresponding to connection pads  101 - 107  provided on the upper and lower peripheral portions of the memory board  100 . The lead pins  121 ,  123 ,  125  and  127  are provided in places corresponding to the lower connection pads of the memory board  100 . The lead pins  122 ,  124 ,  126 , on the other hand, are provided in places corresponding to the upper connection pads of the memory board  100 . A vertical gap between the lower and upper lead pins is determined so that, when once engaged with the memory board  100 , they clip and then hold the memory board  100 . 
     However, the vertical gap between the upper and lower pins is fixed, which makes it impossible to apply one lead frame for various semiconductors or sub-substrates having different thicknesses. 
     SUMMARY OF THE INVENTION 
     Therefore, a purpose of the present invention is to provide a clip-type lead frame having flexibility to several boards with different thickness caused by not only an uneven product quality but also several different type products. 
     To this end, a clip-type lead frame for mounting a first substrate with connection pads on its peripheral portion on a second substrate, comprising: a support made of electrically insulative material; and a first pin and a second lead pin made of electrically conductive material and mounted in the support so that an upper portion of first lead pin opposes to an upper portion of the second lead pin with leaving a gap therebetween for clipping and holding the first substrate, wherein at least one of the first and second lead pins has a mechanism for adjusting the gap between the opposing upper portions of the first and second pins. 
     In another aspect of the present inventions, the upper portions of the first and second lead pin are positioned so that the upper portion of the first lead pin makes a contact with an upper surface of the first substrate and the upper portion of the second lead pin makes a contact with a lower surface of the first substrate, and wherein the adjust mechanism is provided to the first lead pin. 
     In another aspect of the present inventions, the upper portions of the first and second lead pin are positioned so that the upper portion of the first lead pin makes a contact with an upper surface of the first substrate and the upper portion of the second lead pin makes a contact with a lower surface of the first substrate, and wherein the adjust mechanism is provided to the second lead pin. 
     In another aspect of the present inventions, the mechanism comprises an upper part of the lead pin, a lower part of the lead pin separated from the upper part of the lead pin, and a holder defined in one of the upper part and the lower part of the lead pin for holding the other of the upper part and the lower part of the lead pin. Also, the remaining part of the of the lead pin has a deformation for preventing a slip between the upper part and the lower part of the lead pin. Preferably, the deformation may be a corrugated portion. 
     In another aspect of the present inventions, the mechanism has an angled section. 
     In another aspect of the present inventions, the support has an insulating portion which opposes to a peripheral portion of the first substrate held between the first and second lead pins. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a main substrate and a sub-substrate connected by clip-type lead frames according to the first embodiment of the present invention; 
     FIG. 2 is an exploded perspective view of one lead pin of the lead frame; 
     FIG. 3A is a cross sectional view of the lead frame; 
     FIG. 3B is a partial side elevational view of the lead frame; 
     FIG. 3C is a partial top plan view of the lead frame; 
     FIG. 4 is a side elevational view of two memory boards mounted on the main-board by means of the clip-type lead frames; 
     FIG. 5 is a cross sectional view of another embodiment of the clip-type lead frame according to the present invention; 
     FIGS. 6A to  8 B are cross sectional views of another embodiments of the lead frame according to the present invention; and 
     FIG. 9 is a perspective view of the conventional lead frames and the upper and lower substrates connected by the lead frames. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, several embodiments of the present invention will be described in detail hereinafter. It should be noted that like reference numerals designate like parts throughout the drawings. 
     First Embodiment 
     Referring to FIG. 1, there is shown a first substrate  100  mounted on a second substrate  200  by means of clip-type lead frames  10  and  20  of first embodiment according to the present invention. The first substrate  100  and the second substrate  200  may be any electric device such as semiconductor device, a memory device, an electric circuit board, and any combinations thereof. The first substrate  100  has equally spaced connection pads on its opposite peripheral portions, e.g., right and left portions, of upper and lower surfaces. For clarity, only the right connection pads  101 - 107  are illustrated in the drawing. Likewise, electric wires provided on the second substrate  200  are omitted from the drawing. In this embodiment, although the first substrate  100  is supported at its opposite sides by the lead frames, only one lead frame can be employed if the board has connection pads on one side, for example, left or right side. 
     In this embodiment, although the clip-type lead frames  10  and  20  are the same size and configuration, they may be different. Each of the clip-type lead frames  10  and  20  has an elongated support  18  made of electrically insulative material such as synthetic resin for supporting a plurality of inner and outer lead pins  11 - 17  arranged in two lines corresponding to the connection pads  101 - 107  of the first substrate  100 . The inner lead pins  11 ,  13 ,  15  and  17 , made of electrically conductive material, are provided in a one-to-one correspondence with the connection pads  101 ,  103 ,  105  and  107  mounted on the lower surface of the first substrate  100 . The outer lead pins  12 ,  14  and  16 , also made of electrically conductive material, are provided in a one-to-one correspondence with the connection pads  102 ,  104  and  106  mounted on the upper surface of the first substrate  100 . Vertical and horizontal gaps between the inner lead pins  11 ,  13 ,  15  and  17  and the outer lead pins  12 ,  14  and  16  are determined so that they cooperate with each other to clip and hold the first substrate  100  in a stable manner. 
     Referring next to FIG. 2, the inner lead pin  11  as well as other inner lead pins  13 ,  15  and  17  has an upper part  11   a  and a lower part  11   b . The upper part  11   a  is bent at its mid portion at an angle greater than 90 degrees to define a vertical portion and a horizontal portion extending from the top end of the vertical portion. The vertical portion of the upper part  11   a  has a deformation or corrugated section P 1  defined therein. Also, the lower part  11   b  is bent at substantially right angle to define a vertical portion and a horizontal portion. The vertical portion of the lower part  11   b  has a pair of arms P 2  or holder extending from its vertical edges. The arms P 2  are curved inwardly so that the curved arms P 2  cooperate with the vertical portion of the lower part  11   b  to hold the vertical portion, in particular corrugated portion P 1 , of the upper part  11   a  when it is inserted in a gap defined between the vertical portion and the opposing arms P 2  of the lower part  11   b . The gap between the vertical portion and the opposing arms P 2  of the lower part  11   b  is defined so that a vertical position of the inserted upper part  11   a  can be adjusted according to the thickness of the first substrate. 
     Although the corrugated portion P 1  is effective for preventing an unwanted slip of the upper part  11   a  and thereby positioning the upper part  11   a  against the lower part  11   b , it can be eliminated or it can be replaced by another means capable of preventing any possible slip between the upper and lower parts. Additionally or instead, the vertical portion of the lower part  11   b  may be formed with the corrugated portion or provided with another similar means for the positioning of the upper part  11   a  against the lower part  11   b  of the lead pin  11 . Also, the end portion of the opposing arms P 2  may be roughed. 
     Referring to FIGS. 3A to  3 C, the outer lead pin  12  as well as other lead pins  14  and  16 , which is preferably made from a single plate, has a mid portion extending vertically and an upper and a lower portions extending horizontally in the opposite direction. The lower horizontal portion is bent at substantially right angled against the vertical portion while the upper horizontal portion is curved to define an angle of less than 90 degrees with the vertical portion. 
     The lower parts  11   b  of the inner lead pins  11  and the outer lead pins  12  are integrally molded in the support  18  so that the lower horizontal portion of the inner and outer lead pins  11 , 12  are directed outwardly, i.e., in opposite directions. After molding, the upper part  11   a  of the inner lead pin  11  is combined with the corresponding lower part  11   a  by inserting the vertical portion of the upper part  11   a  into the gap defined between the vertical portion and the opposing arms P 2  of the lower part  11   b.    
     Although the vertical portion of the lower part  11   b  is in part molded in the support  18 , it may be totally embedded in the support except for the paired arms P 2 , increasing the rigidity of the lead pin  11 . 
     Also preferably, a portion of the outer lead pin  12  which would oppose the first substrate  100  inserted between the upper and lower horizontal portions of the outer and inner lead pins  11 , 12  is covered with the resin. This prevents any connection pad and/or wire provided at the peripheral edge from making an unnecessary contact with the lead pin  12 . 
     Further, as best shown in FIG. 3A, preferably distal ends of the upper horizontal portions of the inner and outer lead pins  11 , 12  are curved upward and downward, respectively, which eases the insertion the first substrate therebetweeen. 
     After the first substrate  100  is inserted and then held by the lead frames  10  and  20 , the connection pads on the first substrate  100  and the corresponding upper horizontal portions on the connection pads are secured by soldering. Preferably, the upper portion  11   a  and the arms P 2  of the lower portion  11   b  of each inner lead pin is also secured by soldering. Then, the lower horizontal portion of the inner and outer lead pins are placed on the corresponding connection pads on the second substrate  200  and then secured by soldering. 
     FIG. 4 shows the first substrate  100  and another first substrate  110  having a thickness T 2  greater than that Ti of the first substrate  100 . In this instance, the thicker first substrate  110  is also supported by the clip-type lead frame  20 ′ which is similar to the lead frame  101  used for supporting the thinner first substrate  100  simply by adjusting the height of the inner lead pin and thereby expanding the vertical gap between the upper horizontal portions of the inner and outer lead pins. Also, the height of the outer lead pin for supporting the upper surface of the first substrates is fixed, such that the height of the upper surface of the thinner first substrate  100  is maintained the same as that of the thicker first substrate  110 . This is advantageous for the designing of other substrates or housing provided above the substrate  200 . 
     In this embodiment, the lower horizontal portions of the inner and outer lead pins are directed outwardly in opposite orientations. This is effective to prevent the inner lead and the neighboring outer lead from being erroneously connected with each other at soldering. Alternatively, as shown in FIG. 5, the lower horizontal portions of the inner and outer lead pins may be oriented in the same way and away from the first substrate. In this instance, a configuration of a probe for testing the operational features of the first substrate after the board is mounted on the second substrate can be simplified. 
     Second Embodiment 
     Referring to FIG. 6A, there is shown another lead frame of a second embodiment of the present invention, generally indicated by reference numeral  30 . The lead frame  30  has plurality pairs of inner and outer lead pins  31  and  32 . The inner pin  31 , which is made from a plate, is bent at its upper and lower positions to form upper and lower horizontal portions. Preferably, the upper horizontal portion is oriented obliquely and upwardly while the lower horizontal portion is directed substantially horizontally. Similar to the inner lead frame described in the first embodiment, the outer lead frame  32  is made of two parts, i.e., upper part  32   a  and lower part  32   b . The upper part  32   a  has a vertical portion which is corrugated in part and a horizontal portion extending horizontally, more preferably extending obliquely and downwardly. The lower part  32   b , on the other hand, is substantially right angled. Also, the vertical portion of the lower part  32   a  has a pair of arms or holders extending from its opposite vertical edges. These arms are curved back so that they cooperate with the vertical portion of the lower part  32   b  to define a gap into which the vertical portion of the upper part can be inserted and then retained therebetween. 
     The inner lead pin  31  and the lower part  32   b  of the outer lead pin  32  are mounted in the insulation support  33  so that the upper and lower horizontal portions of the inner lead pin  31  is oriented outwardly while the lower horizontal portion and the arms of the lower part  32   b  of the outer lead pin  32  is also directed outwardly. Then, the upper part  32   a  of the outer lead pin  32  is inserted between the vertical portion and the arms of the lower part  32   b  of the outer lead pin  32  so that the upper horizontal portion of the upper part  32   a  is oriented in the same way as the upper horizontal portion of the inner lead pin  31 . 
     Although the lower horizontal portions of the inner and outer lead pins are directed in the opposite directions, as shown in FIG. 6B them may be oriented in the same direction. 
     Third Embodiment 
     Referring to FIGS. 7A and 7B, there is shown another lead frame of a third embodiment of the present invention, generally indicated by reference numeral  40 . This embodiment is a modification of the first embodiment in which the inner lead  41  is angled in its vertical portion to define a square bracket section having a upper horizontal portion, a lower horizontal portion, and a vertical portion connecting the upper and lower horizontal portions. Also, the inner lead  41  is molded in the support  43  so that the upper horizontal portion indicated by P 7  is projected from the support  43 . The outer lead pin  42  is the same as that in the first embodiment. 
     This arrangement allows an increased elastic displacement of the upper horizontal portion P 6  of the inner lead pin  41 , causing the lead frame to be employed for the clipping and holding of the first substrates having different thicknesses. 
     It should be noted that the length of the part of the bracket section molded in the support could be changed as required. 
     Although the inner lead pin  41  is angled in the bracket fashion, it may be angled stepwise as shown the inner lead pin  41 ′ in FIG.  7 B. 
     Also, although the inner lead pin  41  is angled, the outer lead pin  42  may be angled in the manner described above. 
     Fourth Embodiment 
     Referring to FIGS. 8A and 8B, there is shown another lead frame of a fourth embodiment of the present invention, generally indicated by reference numeral  50 . This embodiment is another modification of the first embodiment in which the inner lead  51  is angled in its vertical portion to define an angled bracket section having an upper oblique portion and a lower oblique portion. 
     This arrangement also results in the advantages derived from the third embodiment. Namely, the elasticity of the angled lead pin and the displacement of the upper horizontal portion P 8  can be changed simply by the length of the portion P 9  molded in the support. 
     Although the inner lead pin  51  is angled in the angled bracket fashion, it may be angled stepwise as shown the inner lead pin  51 ′ in FIG.  8 B. 
     Although the inner lead pin  51  is angled, the outer lead pin  52  may be angled in the manner described above. 
     Fifth Embodiment 
     Although in the embodiment described above a mechanism is provided for either inner or outer lead pin for changing the height of its upper horizontal portion, it may be provided to both lead pins. This increases the height adjustment of the upper and lower limits of the first substrate. 
     It should be noted that the present application is based upon the Japanese Patent Application No. 2001-394686 which is entirely incorporated herein by reference.