Printing circuit board with traces in an insulator

A printing circuit board includes: an insulator having an upper surface, a lower surface and an opening formed in the lower surface, and a trace having an upper surface, a lower surface and a side edge and received in said insulator. The upper surface of said trace is exposed out of the insulator and a portion of the lower surface of said trace is exposed by said opening for external connection.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a Printing Circuit Board, and more particularly related to a PCB which is comprised of an insulator and a trace embedded therein, wherein both the upper surface of trace and a portion of the lower surface of trace exposed to the atmosphere for connecting external substance.

2. Description of the Related Art

Nowadays, both science and technology are developing rapidly, meanwhile, electrical devices are designed for thinner, wider application, lower cost, and better reliability, wherein in order to achieve above objects, the manufacturers keep on developing it.

FIG. 9shows a conventional PCB52comprised of: an insulator40which is made of FR-4 or BT (Bismaleimide Triazine) or epoxy etc. having a blind via44, an upper surface41and a lower surface42; said blind via44is for accommodating a portion of trace7A; a ball pad7B which is made of metal such as copper for external connection (e.g. solder ball), said ball pad7B having a side edge7B3, an upper surface7B1, and a lower surface7B2, wherein both said side edge7B3and a portion of lower surface7B2of trace7A encapsulated by said insulator40, wherein another portion of lower surface7B2exposed to blind via44for being coupled with said trace7A, said upper surface7B1of ball pad7B exposed out of the lower surface42of insulator40for external connection (i.e. said upper surface7B1of ball pad7B exposed to atmosphere for external connection); a trace7A which is made of metal such as copper for being employed as a path of transmitting electrical current, said trace7A having a side edge7A3, an upper surface7A1and a lower surface7A2, wherein said lower surface7A2coupled with said upper surface41of insulator40, a portion of trace7A accommodated in said blind via44, in this manner, said trace7A electrically connected to said ball pad7B through said blind via44; a solder mask80covering both said upper surface41of insulator40and a portion of said trace7A, wherein another portion of said trace7A being exposed to the atmosphere for external connection; and a plurality of conductive layers90which are made of nickel, gold, silver or the like are valuable and expensive, said conductive layers90coupled with said upper surface7B1of ball pad7B and the portion of trace7A exposed to atmosphere (i.e. both said another portion of upper surface7A1and said side edge7A3) respectively; accordingly, (1). The path of transmitting electrical current from the upper surface41of insulator40to the lower surface42of insulator40of said conventional PCB52is from the upper surface7A1of trace7A through said blind via44of insulator40to said upper surface7B1of ball pad7B; (2). said solder mask80having a thickness Ta which is comprised of a thickness T81and a thickness T82, wherein said thickness T81is the distance between the upper surface7A1of trace7A and the upper surface41of insulator40, said thickness T82is the distance between the upper surface of said solder mask80and the upper surface7A1of trace7A, consequently, according to the features of conventional PCB52mentioned above, the thickness T52which is included the thickness T4of insulator40and thickness Ta becomes thicker, in this manner, it is not convenient for said conventional PCB52to be used in the electronic industries; (3). said side edge7A3of trace7A also needs to be covered with said conductive layer90, in this manner, more material needs to be used, then the cost for manufacturing said conventional PCB52becomes higher; and (4). Due to there is not any solder mask coupled with the lower surface42of insulator40, then said ball pad7B can't be employed as a path of transmitting electrical current but be employed as a terminal for external connection (e.g. solder ball) exclusively, in this manner, said ball pad7B enables not to be layout on said lower surface42of insulator40freely, moreover, said ball pad7B is oxidized and damaged easily without solder mask protecting; meanwhile, due to it is difficult for the width “W” of ball pad7B to be changed, when said ball pad7B coupled with said lower surface42of insulator40, then it is restricted for said conventional PCB52to be used in electronic industry; For example: in case that the volume of solder ball (not shown) is unchanged, and the height of solder ball is needed to be decreased (i.e. said width “W” of ball pad7B is needed to become wider for reaching the demand mentioned above), nevertheless, due to said width “W” of ball pad7B can't be changed to become wider for reaching said demand when said ball pad7B coupled with said lower surface42of insulator40, then the height of solder ball7B can't be reached to the qualification of electrical device(s) such as PBGA or CSP, in this manner, said conventional PCB52enables not to be invited to said electrical devices, as this result, the application of said conventional PCB52is restricted.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to solve the mentioned-above problems, in accordance with the invention, the PCB includes an insulator and a plurality of traces, wherein said traces are embedded in the insulator, and wherein both the upper surface and a portion of the lower surface of said trace exposed out of said insulator, in this manner, both said upper surface and said portion of the lower surface of said trace exposed to atmosphere for connecting external substance, nevertheless, another portion of the lower surface of trace encapsulated by said insulator, in this manner, it is not necessary for said lower surface of trace to be coupled with a solder mask which is for protecting said lower surface of trace, as this result, the advantages of said PCB includes: (1). the cost is saved; (2). the thickness is thinner; (3). the reliability of said PCB is enhanced; (4). the blind via can be omitted; and (5). it is more convenient for the PCB to be used in electronic industries in accordance with the present invention, moreover, the trace of PCB can further include an extending portion.

The aforementioned and further objects of the present invention will more adequately appeared from the detailed description, accompanying drawings and appended claims as follow.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will be explained with reference to the drawings as follow.

FIG. 2shows a PCB55in accordance with the present invention, said structure of PCB55is similar to the structure of PCB50shown inFIG. 1, the differences between said PCB55and said PCB50are: (1). the upper surface71of trace70of PCB55is below the upper surface41of insulator40, in this manner, said upper surface71of trace70is not co-planar to said upper surface41of insulator40; wherein the upper surface71of trace70enables to be protruding the upper surface41of insulator40(refer toFIG. 5orFIG. 6), said upper surface71of trace70is not co-planar to said upper surface41of insulator40either while the upper surface71of trace70protruding the upper surface41of insulator40, accordingly, it is optional that the upper surface71of trace70is below the upper surface41of insulator40; and (2). the second lower surface722of trace70is below the first lower surface721of trace70, in this manner, said second lower surface722of trace70is not co-planar to said first lower surface721of trace50, in this manner, said trace70further having a second side edge732which is between said first lower surface721and said second lower surface722of trace70, said second side edge732of trace70placed in said recess48of insulator40too, Consequently, due to said second side edge732of trace70, the area that said trace70contacted to the conductive layer90which is coupled with the second lower surface722of trace70enables to be increased, then it allows said conductive layer90to be not only coupled with the second lower surface722but also coupled with said second side edge732of trace70, in this manner, said conductive layer90enables to be coupled with said trace70more securely, then it can prevent said conductive layer90from peeling off said trace70, and then the reliability of said PCB50can be enhanced, accordingly, due to said second side edge732of trace70, in case that either a conductive material such as an another trace (refer toFIG. 3) or an isolative material such as a solder mask (refer toFIG. 4) coupled with said second side edge732, the reliability of said PCB50can be enhanced; wherein the second lower surface722of trace70enables to be protruding the first lower surface721of trace70(not shown), as this result, said second lower surface722of trace70is not co-planar to said first lower surface721of trace70either, accordingly, it is optional that the second lower surface722of trace70is below the first lower surface721of trace70; furthermore, either the conductive layer90coupled with the upper surface71of trace70or the conductive layer90coupled with the second lower surface722(associated with the second side edge732) of trace70can be protruding (or below) the upper surface41or the lower surface42of insulator40as required.

FIG. 3shows a PCB50in accordance with the present invention, said structure of PCB50is similar to the structure of PCB55shown inFIG. 2, the difference between said PCB50and said PCB55is: said PCB50further comprising an another trace75which is coupled with the lower surface42of insulator40, in this manner, said another trace75enables to be lay out on said lower surface42of insulator40freely, and wherein a portion of said another trace75is placed within said recess48of insulator40and is coupled with both the second lower surface722and the second side edge732of trace70, By means of said second side edge732of trace70, the area that said another trace75contacted to the trace70enables to be increased, (i.e. it allows said another trace75to be not only coupled with the second lower surface722but also coupled with said second side edge732of trace70), in this manner, said another trace75enables to be coupled with said trace70more securely, then it can prevent said another trace75from peeling off said trace70, and then the reliability of said PCB50can be enhanced; In additional, a further another trace(s) (not shown) or an another insulator(s) (not shown) can be coupled with the lower surface42of insulator40, in this manner, said PCB55is employed as a multi-layer PCB.

FIG. 4shows a PCB50in accordance with the present invention, said structure of PCB50is similar to the structure of PCB55(shown inFIG. 2), the differences between said PCB50and said PCB55are: (1). said PCB50further comprising a solder mask80which is coupled with the lower surface42of insulator40, wherein a portion of said solder mask80is placed in said recess48of insulator40and is coupled with both the second lower surface722and the second side edge732of trace70, By means of said second side edge732of trace70, the area that said solder mask80contacted to the trace70enables to be increased, (i.e. it allows said solder mask80to be not only coupled with a portion of the second lower surface722but also coupled with said second side edge732of trace70), in this manner, said solder mask80enables to be coupled with said trace70more securely, then it can prevent said solder mask80from peeling off said trace70, and then the reliability of said PCB50can be enhanced; and (2). Due to a portion of said solder mask80is placed within said recess48of insulator40and is coupled with said second lower surface722of trace70, then the width “W” of second lower surface722enables to become shorter, and then the materials of said conductive layer90coupled with the second lower surface722can be saved, in this manner, the cost for manufacturing said PCB50can be saved, and it is good to electronic industry.

FIG. 5shows a PCB55comprising: an insulator40having an upper surface41and a lower surface42; a trace70having an upper surface71, a lower surface72and a side edge73, wherein said side edge73consists of a first side edge731and a third side edge733, said first side edge731and said third side edge733are co-planar, said trace70embedded in said insulator40, in this manner, said trace70is encapsulated by said insulator40, wherein said first side edge731of side edge73and said lower surface72of trace70are encapsulated by said insulator40, and wherein said upper surface71of trace70is protruding said upper surface41of insulator40and said third side edge733of side edge73is protruding said upper surface41of insulator40too, in this manner, both said upper surface71of trace70and said third side edge733of side edge73exposed to atmosphere (i.e. both said upper surface71of trace70and said third side edge733of side edge73exposed out of said upper surface41of insulator40) for connecting external substance(s), moreover, said trace70can be employed as either a ball pad or a path of transmitting electrical current; a solder mask80covering said upper surface41of insulator40and a portion of said upper surface71of trace70for protection, wherein another portion of said upper surface71of trace70exposed to the atmosphere for connecting external substance, wherein said solder mask80is optional; accordingly, By means of said upper surface71of trace70which is protruding the upper surface41of insulator40, it allows the thickness of said trace70to become thicker, in this manner, said PCB55enables to respond the demand of high current and high speed transmission, then it is more convenient for said PCB55to be used in electronic industries; In addition, said insulator40can further have a recess (refer toFIG. 6; numeral “48”) on the lower surface42of insulator40as required, in case that said insulator40further having a recess (48), then a portion of said lower surface72of trace70can be placed therein and exposed to atmosphere (i.e. said a portion of lower surface72of trace70exposed out of said lower surface42of insulator40) for connecting external substance(s); Moreover, said first side edge731and said third side edge733enable to be not co-planar (refer toFIG. 7; numerals “731” and “733”) as required.

FIG. 6shows a PCB55in accordance with the present invention, said structure of PCB55is similar to the structure of PCB50(shown inFIG. 1), the differences between said PCB55and said PCB50are (1). said side edge73consists of a first side edge731and a third side edge733, said first side edge731and said third side edge733are co-planar, wherein said first side edge731of side edge73and said first lower surface721of trace70are encapsulated by said insulator40, wherein said upper surface71of trace70is protruding said upper surface41of insulator40and said third side edge733of side edge73is protruding said upper surface41of insulator40too, in this manner, both said upper surface71of trace70and said third side edge733of side edge73exposed to atmosphere, in this manner, it allows that said trace70further having an extending portion (refer to the detailed descriptions ofFIG. 7) which is extending on the upper surface41of insulator40and the thickness of said trace70enables to become thicker; and (2). Said trace70further having a dimple724which is on the second lower surface722and is exposed to the atmosphere, in this manner, the second lower surface722is uneven (i.e. not flat), meanwhile, By means of said dimple724of trace70, the area that said second lower surface722of trace70contacted to external substance(s) (such as solder ball, conductive wire, conductive layer, resistor, capacitor, and/or another trace) enables to be increased, in this manner, said trace70enables to be coupled with said external substance more securely, then it can prevent said external substance from peeling off said trace70, and then the reliability of said PCB55can be enhanced, wherein the depth (not shown) of said dimple724can be 1 μm, 2 μm or more than 2 μm. In additional, said trace70also can further have a second side edge (refer toFIG. 2; numeral“732”)

FIG. 7shows a PCB50in accordance with the present invention, said structure of PCB50is similar to the structure of PCB55(shown inFIG. 6), the differences between said PCB50and said PCB55are (1). said trace70of PCB50further having an extending portion74which is a portion of said trace70, said extending portion74having an upper surface741and a lower surface742, said lower surface742of extending portion74coupled with said upper surface41of insulator40, in this manner, said extending portion74enables to be extended on said upper surface41of insulator40freely, as this result, it is more convenient for said PCB50to be used in the electronic industry; and wherein said side edge73consists of a first side edge731and a third side edge733, said first side edge731and said third side edge733are not co-planar, wherein said first side edge731of side edge73and said first lower surface721of trace70are encapsulated by said insulator40, and wherein said upper surface71of trace70is protruding said upper surface41of insulator40and said third side edge733of side edge73is protruding said upper surface41of insulator40too, in this manner, both said upper surface71of trace70and said third side edge733of side edge73exposed to atmosphere, meanwhile, said upper surface71of trace70comprised of a first upper surface711and a second upper surface712, and wherein both said first upper surface711and said second upper surface712are not co-planar, said first upper surface711is protruding the upper surface41of insulator, meanwhile, a portion of said first upper surface711, said second upper surface712of trace70and said upper surface41of insulator40are covered with the solder mask80, wherein said upper surface741of extending portion74is employed as a portion of said upper surface71of trace70, in this manner, said upper surface71of trace70further includes said upper surface741of extending portion74, and wherein said upper surface741of extending portion74(i.e. a portion of said upper surface71of trace70) exposed to the atmosphere for connecting external substance; furthermore, the second upper surface712of trace70enables to be co-planar to the first upper surface721of trace70as required, accordingly, it is optional that the first upper surface711of trace70is not co-planar to the second upper surface712of trace70; and (2). the second lower surface722is uneven such as conical and/or curvy or the like, in this manner, the area that said second lower surface722contacted to external substance(s) enables to be increased, then it can prevent said external substance from peeling off said trace70, and then the reliability of said PCB50is enhanced, in addition, said extending portion74and said trace70can be unitary or said extending portion74and said trace70can be made of different metals.

FIG. 8shows a package30which is involved in a PCB55in accordance with the present invention, said structure of PCB55(shown inFIG. 8) is similar to the structure of PCB55(shown inFIG. 2), wherein the difference between said PCB55(FIG. 8) and said PCB55(FIG. 2) is: there is not any conductive layer (90) coupled with the second lower surface722of trace70(shown inFIG. 8), compared with the second lower surface722of trace70(shown inFIG. 2); said package30further comprised of: a chip20which is coupled with said solder mask80on the upper surface41of insulator40; a conductive wire95which is electrically connected said chip20to said PCB55; an encapsulant60which is made of SUMITOMO G1250 or the like, said encapsulant60seals said PCB55, said chip20and said conductive wire95; and a solder ball96, wherein said solder ball96coupled with said second lower surface722and said second side edge732, accordingly, said PCB55enables to be coupled with said chip20and said encapsulant60, wherein said chip20can be employed as a flip chip, in case of flip chip, then said chip20coupled with said PCB55through a plurality of conductive bumps and sealed by an adhesive means such as encapsulant; moreover, in case that said package30coupled with a mother board (not shown) by said solder ball96, once said package30is attacked by an impact, due to the area that said second lower surface722(associated with said second side edge732) of trace70contacted to said solder ball96is increased, then it allows said solder ball96enables to be coupled with said trace70more securely, then it can prevent said conductive layer90from peeling off said trace70, and then the reliability of said PCB50can be enhanced. Furthermore, due to the first lower surface721of trace70encapsulated by said insulator40, accordingly, said trace70can be held by said insulator40firmly too, in this manner, it can prevent said trace70from peeling off said insulator40while impacting, and then the reliability of said PCB55can be enhanced, consequently, By means of the second side edge732or the first lower surface721of trace70which is encapsulated by said insulator40, the reliability of said PCB55enables to be enhanced.

In accordance with the foregoing descriptions accompanying drawings, this invention has been described in terms of several preferred embodiments, various alternations and modifications can be made to become apparent to those skilled in the art; For examples: as shown inFIG. 1, wherein the second lower surface722enables to be not co-planar to the first lower surface721of trace70as required, then said trace70also having a second side edge (732), moreover, the upper surface71of trace enables to be protruding the upper surface41of insulator40, furthermore, an another trace75can be instead of said conductive layer90as required too; Accordingly, since many such various alterations and/or modifications can be made to the foregoing descriptions, it is to be understood that the scope of the invention is not limited to the disclosed embodiments but is defined by the appended claims.