JP4084508B2

JP4084508B2 - Circuit board

Info

Publication number: JP4084508B2
Application number: JP24263499A
Authority: JP
Inventors: 祥司植垣; 慎吾佐藤; 清吾松園
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 1999-08-30
Filing date: 1999-08-30
Publication date: 2008-04-30
Anticipated expiration: 2019-08-30
Also published as: JP2001068507A

Description

【０００１】
【発明の属する技術分野】
本発明は、半導体装置等の電子部品が接続、搭載される回路基板に関するものである。
【０００２】
【従来の技術】
近年、半導体素子を半導体素子収納用パッケージに収容して成る半導体装置等の電子部品をプリント配線基板等の回路基板に実装する方法として、半導体装置等の下面に形成した外部端子を回路基板の上面に形成した接続パッドに半田等から成る金属バンプを介して接続する、所謂、フリップチップ方式の実装方法が多用されつつある。
【０００３】
上記フリップチップ方式の実装方法に使用される半導体装置は、一般にアルミナセラミックス等から成り、上面に半導体素子が載置される載置部を有し、該載置部または載置部周辺から下面にかけて導出する複数個のメタライズ配線層を有する絶縁基板と、絶縁基板の下面に位置するメタライズ配線層に取着されている金属バンプとからなる半導体素子収納用パッケージを準備し、絶縁基板の上面に半導体素子を載置し、該半導体素子の各電極をメタライズ配線層にボンディングワイヤ等の電気的接続手段を介して電気的に接続するとともに半導体素子を例えば、モールド樹脂で気密に封止することによって製作されている。
【０００４】
また、半導体装置等がフリップチップ実装法により実装される回路基板は、通常、エポキシ樹脂等の電気絶縁材料から成り、上面に半導体装置の載置部を有する絶縁基体と、絶縁基体の前記載置部表面に形成され、前記半導体装置の金属バンプが接続される複数個の接続パッドと、各接続パッドと１対１に対応して形成された複数個のビア導体と、各対応する接続パッドとビア導体とを導通する複数個の引き出し線とから形成されており、各ビア導体は絶縁基体の内部及び／または下面に形成された配線層と導通され、この配線層を介して他のビア導体や外部の電気回路と電気的に接続されている。
【０００５】
そして、半導体装置の回路基板への実装は、半導体装置を回路基板上に、半導体装置の下面に位置する金属バンプを回路基板の接続パッドに当接するようにして載置し、次にこれを所定温度に加熱し、金属バンプを溶融させ、半導体装置の下面に位置するメタライズ配線層と回路基板の接続パッドとを溶融した金属バンプで接合させることによって行われる。
【０００６】
なお、前記回路基板の各接続パッドは半導体装置等の金属バンプに対して１対１に対応するよう配置されており、また前記各接続パッドに対応するビア導体は各接続パッドに近い領域のうち、前記配線層の引き回しパターンに最も都合のよい位置に形成されている。
【０００７】
【発明が解決しようとする課題】
しかしながら、上記従来の回路基板においては、半導体装置の絶縁基板を構成する酸化アルミニウム質焼結体等の熱膨張係数が４×１０^-6／℃〜７×１０^-6／℃であるのに対し、回路基板の絶縁基体を構成するエポキシ樹脂等の熱膨張係数が２×１０^-5／℃〜５×１０^-5／℃であり、大きく相違するため半導体装置の絶縁基板及び回路基板の絶縁基体に半導体素子が作動等に発生した熱等が印加されると半導体装置と回路基板との間で、回路基板の半導体装置が搭載される搭載部の中心部に向かう方向に前記熱膨張係数の相異に起因する大きな応力が発生すること、半導体装置と回路基板とを接続する金属バンプの機械的強度は回路基板の接続パッドと引き出し線との接続部分が最も弱く、従来の回路基板においては、接続パッドに対応するビア導体が回路基板の配線層の引き回しパターンを優先的に考慮した位置に形成されており、ビア導体が接続パッドに対し半導体装置が搭載される搭載部の中心部に向かう方向に位置、即ち、接続パッドとビア導体とを接続する引き出し線が半導体装置の搭載される搭載部の中心部に向かう方向に位置している場合が多々あり、金属バンプの機械的強度の最も弱い部分が半導体装置と回路基板との間に発生する応力の作用方向にあること等から金属バンプに半導体装置と回路基板との間に発生した応力が作用すると金属バンプに破断が容易に発生し、半導体装置等と回路基板との接続の信頼性が低いものとなる欠点を有していた。
【０００８】
本発明は上記欠点に鑑み案出されたものであり、その目的は、半導体装置等の電子部品がフリップチップ方式で実装される回路基板において、電子部品と回路基板との電気的接続を長期にわたって維持することが可能な長期信頼性に優れた回路基板を提供することにある。
【０００９】
【課題を解決するための手段】
本発明の回路基板は、上面に電子部品が載置される載置部を有し、該電子部品の絶縁基板よりも熱膨張係数が大きい絶縁基体と、前記載置部上に該載置部全体に渡って配置され、電子部品の電極が接続される複数個の接続パッドと、前記各接続パッドに１対１に対応し、前記載置部の表面から内部にかけて形成されている複数個のビア導体と、前記接続パッドとビア導体とを接続する複数個の引き出し線とを有する回路基板であって、前記各ビア導体は、該ビア導体に対応する接続パッドの中心点と電子部品が載置される載置部の中心点とを結ぶ線に垂直な該接続パッドの中心点を通る直線に関して、前記載置部の中心点の反対側に位置することを特徴とするものである。
【００１０】
本発明の回路基板によれば、ビア導体が、そのビア導体に対応する接続パッドと電子部品が載置される載置部の中心点とを結ぶ線に対し垂直方向よりも外側に位置させたことから、電子部品と回路基板を接続する金属バンプの強度が最も弱い位置が電子部品の絶縁基体と回路基板の絶縁基体との熱膨張係数の相異に起因して発生する応力の方向に対し外れた位置となり、その結果、金属バンプの破断が有効に防止され、電子部品と回路基板との電気的接続を長期間にわたって維持することが可能となる。
【００１１】
【発明の実施の形態】
次に本発明を添付図面に基づいて詳細に説明する。
【００１２】
図１は本発明の回路基板の一実施例を示し、図２はその要部拡大図である。図において、１は回路基板、２は絶縁基体、３は接続パッド、４は前記接続パッドと１対１に対応し、絶縁基体１の表面から内部にかけて形成されたビア導体、５は前記接続パッド３とビア導体４とを接続する引き出し線である。
【００１３】
前記絶縁基体２はその上面に半導体装置等の電子部品が載置、実装される載置部２ａを有しており、該載置部２ａに載置、実装される半導体装置等の電子部品を支持する支持部材として作用する。
【００１４】
前記絶縁基体２はガラス繊維を織り込んだ布にエポキシ樹脂を含浸させたガラスエポキシ樹脂や、ガラス繊維を織り込んだ布にビスマレイミドトリアジン樹脂を含浸させたビスマレイミドトリアジン樹脂等の電気絶縁材料で形成されており、例えば、ガラスエポキシ樹脂から成る場合であれば、無アルカリガラスから成るガラス繊維を縦横に織り込んで形成したガラス布にエポキシ樹脂前駆体を含浸させるとともに前記前駆体を半硬化させてプリプレグを形成し、これを必要に応じて積層し、その後熱硬化させることによって製作される。
【００１５】
また前記絶縁基体２はその上面で半導体装置等の電子部品が載置、実装される載置部２ａに接続パッド３が形成されており、該接続パッド３には半導体装置等の電子部品が半田等からなる金属バンプを介して接続される。
【００１６】
前記接続パッド３は実装される電子部品の電極と１対１に対応するように絶縁基体２の載置部２ａに配列形成されており、銅等の金属材料から成り、例えば、絶縁基体２の載置部２ａ上に銅箔を熱圧着するとともにその表面に銅めっき層を所定の厚さに被着させ、これを所定の形状にエッチング加工することにより形成される。
【００１７】
前記接続パッド３は円形、楕円形、四角形、多角形等種々の形状に形成され、、特に円形状とすると、その上面に半導体装置等の電子部品を半田等からなる金属バンプを介して接続するとき、金属バンプの特定の部位に応力が集中することがなく分散し、金属バンプの機械的強度を強くすることができる。従って、前記接続パッド３は円形状としておくことが好ましい。
【００１８】
また前記接続パッド３を円形状とした場合、その直径を、これに金属バンプを介して接続される電子部品の接合部の径と同じ乃至それより０．１ｍｍ程度小さいものとしておくと、回路基板の接続パッド３及び電子部品に対する金属バンプの接合強度を略同一となすことができ、金属バンプと回路基板の接続パッド３との接合部または金属バンプと電子部品との接合部においてどちらか一方に応力が集中することはなく、どちらか一方の接合部に剥離等が優先的に発生するのを有効に防止して長期信頼性をより一層優れたものとなすことができる。
【００１９】
更に前記接続パッド３はその露出する表面にニッケル／金や半田（錫−鉛系合金）等の良導電性で半田濡れ性が良好な金属から成るめっき層（図示せず）を電解めっき法や無電解めっき法等によって１μｍ乃至２０μｍの厚みに被着させておくと、接続パッド３への金属バンプの接合接続をより一層容易、かつ確実なものとなすことができる。従って、前記接続パッド３はその露出する表面にニッケル／金や半田（錫−鉛系合金）等の良導電性で半田濡れ性が良好な金属から成るめっき層を電解めっき法や無電解めっき法等によって１μｍ乃至２０μｍの厚みに被着させておくことが好ましい。
【００２０】
前記絶縁基体２はまたその表面から内部にかけて複数個のビア導体４が形成されており、該ビア導体４の各々は各接続パッド３に対し１対１に対応しており、後述する引出し線５を介して接続パッド３に接続されている。
【００２１】
前記ビア導体４は接続パッド３に接続される電子部品の電極を外部電気回路や絶縁基体２の内部等に形成される配線層に電気的に接続する作用をなす。
【００２２】
前記ビア導体４は、銅等の金属材料から成り、例えば、絶縁基体２にドリル加工やレーザー加工を施すことによりビアホールを形成し、次に従来周知のめっき法及びエッチング法を採用することによってビアホールの内壁に上端を絶縁基体２の上面に導出させた状態で被着させることによって形成される。
【００２３】
前記ビア導体４はそれに対応する接続パッド３に引き出し線５を介して電気的に接続されている。
【００２４】
前記引き出し線５は、銅等の金属から成り、接続パッド３と同様の方法によってビア導体４とそれに対応する接続パッド３とを接続するようにして絶縁基体２に形成される。
【００２５】
なお、前記ビア導体４及び引き出し線５は、絶縁基体２を形成する樹脂と同様のエポキシ樹脂等の樹脂で被覆しておくと、ビア導体４及び引き出し線５の酸化腐蝕を有効に防止することができる。従って、前記ビア導体４及び引き出し線５は、その表面を絶縁基体２を形成する樹脂と同様の樹脂、例えば、エポキシ樹脂等で被覆しておくことが好ましい。
【００２６】
本発明においては、図２に示す如く、ビア導体４を、該ビア導体４と対応する接続パッド３と電子部品が載置される載置部２ａの中心点とを結ぶ線６に対し垂直方向７よりも外側に位置させておくことが重要である。
【００２７】
各接続パッド３に対応するビア導体４を、該ビア導体４と対応する接続パッド３と電子部品が載置される載置部２ａの中心点とを結ぶ線６に対し垂直方向７または垂直方向７よりも外側に位置させておくと、電子部品と回路基板１の接続パッド３とを接続する半田等からなる金属バンプの強度が最も弱い位置、即ち、回路基板１の接続パッド３と引き出し線５との接続部分の位置が電子部品と回路基板１との間に両者の熱膨張係数の相異に起因して発生する応力の作用方向に対し外れた位置となり、その結果、金属バンプの破断が有効に防止され、電子部品と回路基板１との電気的接続を長期間にわたって維持することが可能となる。
【００２８】
従って、前記各ビア導体４は、該ビア導体４に対応する接続パッド３と電子部品が載置される載置部２ａの中心点とを結ぶ線６に対し垂直方向７または垂直方向７よりも外側に位置させておく必要がある。
【００２９】
また、前記接続パッド３とビア導体４とを接続する引き出し線５は、その幅が５０μｍ未満となると接続パッド３との接触部分が小さくなって電気抵抗が増大し、回路基板１の電気特性が劣化するおそれがあり、１５０μｍを超えると、金属バンプが引き出し線５上に多量に流入し、金属バンプのボリューム不足等を生じ易くなる。従って、前記引き出し線５は、その幅を５０μｍ〜１５０μｍの範囲とすることが好ましく、かつ上記範囲内で、対応する接続パッド３の直径の１／２以下としておくことが好ましい。
【００３０】
なお、本発明は上述の実施例に限定されるものではなく、本発明の要旨を逸脱しない範囲であれば種々の変更は可能である。
【００３１】
【発明の効果】
本発明の回路基板によれば、各ビア導体が、該ビア導体に対応する接続パッドの中心点と電子部品が載置される載置部の中心点とを結ぶ線に垂直な該接続パッドの中心点を通る直線に関して、前記載置部の中心点の反対側に位置させたことから、電子部品と回路基板を接続する金属バンプの強度が最も弱い位置が電子部品の絶縁基体と回路基板の絶縁基体との熱膨張係数の相異に起因して発生する応力の方向に対し外れた位置となり、その結果、金属バンプの破断が有効に防止され、電子部品と回路基板との電気的接続を長期間にわたって維持することが可能となる。
【図面の簡単な説明】
【図１】本発明の回路基板の一実施例を示す平面図である。
【図２】図１に示す回路基板の要部拡大図である。
【符号の説明】
１・・・・回路基板
２・・・・絶縁基体
３・・・・接続パッド
４・・・・ビア導体
５・・・・引き出し線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit board on which an electronic component such as a semiconductor device is connected and mounted.
[0002]
[Prior art]
In recent years, as a method of mounting an electronic component such as a semiconductor device in which a semiconductor element is contained in a package for housing a semiconductor element on a circuit board such as a printed wiring board, external terminals formed on the lower surface of the semiconductor device or the like are connected to the upper surface of the circuit board. A so-called flip-chip mounting method is often used in which the connection pads are connected to each other through metal bumps made of solder or the like.
[0003]
A semiconductor device used in the flip-chip mounting method is generally made of alumina ceramic or the like, and has a mounting portion on which a semiconductor element is mounted on the upper surface, and the mounting portion or from the periphery of the mounting portion to the lower surface. A package for housing a semiconductor element comprising an insulating substrate having a plurality of metallized wiring layers to be led out and metal bumps attached to a metallized wiring layer located on the lower surface of the insulating substrate is prepared, and a semiconductor is provided on the upper surface of the insulating substrate. An element is mounted, and each electrode of the semiconductor element is electrically connected to the metallized wiring layer through an electrical connection means such as a bonding wire, and the semiconductor element is hermetically sealed with, for example, a mold resin. Has been.
[0004]
In addition, a circuit board on which a semiconductor device or the like is mounted by a flip chip mounting method is usually made of an electrically insulating material such as an epoxy resin, and an insulating base having a mounting portion for the semiconductor device on an upper surface, A plurality of connection pads formed on the surface of the semiconductor device, to which the metal bumps of the semiconductor device are connected, a plurality of via conductors formed in a one-to-one correspondence with the connection pads, and the corresponding connection pads; Each of the via conductors is electrically connected to a wiring layer formed inside and / or on the lower surface of the insulating base, and other via conductors are connected via the wiring layer. Or electrically connected to an external electrical circuit.
[0005]
The semiconductor device is mounted on the circuit board by placing the semiconductor device on the circuit board so that the metal bumps located on the lower surface of the semiconductor device are in contact with the connection pads of the circuit board, and then mounting the semiconductor bump on the circuit board. This is performed by heating to a temperature, melting the metal bumps, and joining the metallized wiring layer located on the lower surface of the semiconductor device and the connection pads of the circuit board with the molten metal bumps.
[0006]
The connection pads of the circuit board are arranged so as to correspond to the metal bumps of the semiconductor device or the like in a one-to-one correspondence, and the via conductors corresponding to the connection pads are in the region close to the connection pads. The wiring layer is formed at the most convenient position for the routing pattern.
[0007]
[Problems to be solved by the invention]
However, in the conventional circuit board, the thermal expansion coefficient of the aluminum oxide sintered body or the like constituting the insulating substrate of the semiconductor device is 4 × 10 ⁻⁶ / ° C. to 7 × 10 ⁻⁶ / ° C. Since the thermal expansion coefficient of the epoxy resin or the like constituting the insulating substrate of the circuit board is 2 × 10 ⁻⁵ / ° C. to 5 × 10 ⁻⁵ / ° C., which is largely different, the insulating substrate of the semiconductor device and the insulating substrate of the circuit substrate When the heat generated by the operation of the semiconductor element is applied to the semiconductor element, the phase of the thermal expansion coefficient is increased between the semiconductor device and the circuit board in a direction toward the center of the mounting portion on which the semiconductor device of the circuit board is mounted. The large stress caused by the difference occurs, and the mechanical strength of the metal bumps connecting the semiconductor device and the circuit board is the weakest at the connection part between the connection pad and the lead wire of the circuit board. Corresponding to connection pad A conductor is formed at a position preferentially considering the routing pattern of the wiring layer of the circuit board, and the via conductor is positioned in the direction toward the center of the mounting portion on which the semiconductor device is mounted with respect to the connection pad, that is, In many cases, the lead wire connecting the connection pad and the via conductor is located in the direction toward the center of the mounting portion on which the semiconductor device is mounted, and the portion with the weakest mechanical strength of the metal bump is the semiconductor device. If the stress generated between the semiconductor device and the circuit board acts on the metal bump because the stress is generated in the direction of the stress generated between the circuit board and the circuit board, the metal bump easily breaks. There was a drawback that the reliability of connection with the substrate was low.
[0008]
The present invention has been devised in view of the above-described drawbacks, and the object of the present invention is to provide long-term electrical connection between an electronic component and a circuit board in a circuit board on which an electronic component such as a semiconductor device is mounted by a flip-chip method. An object of the present invention is to provide a circuit board excellent in long-term reliability that can be maintained.
[0009]
[Means for Solving the Problems]
Circuit board of the present invention, have a mounting portion on which the electronic components on the top surface is placed, the placing portion the thermal expansion coefficient is large insulating substrate than the insulating substrate of the electronic component, on the mounting portion disposed throughout, a plurality of connection pads on which the electronic components of the electrode are connected, the one-to-one correspondence to each connection pad, a plurality of which are formed from the surface to the inside of the mounting portion and the via conductor, a circuit board having a plurality of lead lines for connecting the connecting pads and the via conductors, wherein each via conductor, the center point and the electronic component connection pads corresponding to the via conductor mounting The straight line passing through the center point of the connection pad perpendicular to the line connecting the center point of the placement part to be placed is located on the opposite side of the center point of the placement part.
[0010]
According to the circuit board of the present invention, the via conductor is positioned outside the vertical direction with respect to the line connecting the connection pad corresponding to the via conductor and the center point of the placement portion on which the electronic component is placed. Therefore, the position where the strength of the metal bump connecting the electronic component and the circuit board is the weakest is the direction of the stress generated due to the difference in the thermal expansion coefficient between the insulating base of the electronic component and the insulating base of the circuit board. As a result, the metal bump is effectively prevented from being broken, and the electrical connection between the electronic component and the circuit board can be maintained for a long period of time.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail with reference to the accompanying drawings.
[0012]
FIG. 1 shows an embodiment of a circuit board according to the present invention, and FIG. In the figure, 1 is a circuit board, 2 is an insulating base, 3 is a connection pad, 4 is a one-to-one correspondence with the connection pad, a via conductor formed from the surface of the insulating base 1 to the inside, and 5 is the connection pad. 3 is a lead line connecting 3 and the via conductor 4.
[0013]
The insulating base 2 has a mounting portion 2a on which an electronic component such as a semiconductor device is mounted and mounted on the upper surface, and the electronic component such as a semiconductor device mounted and mounted on the mounting portion 2a. Acts as a supporting member to support.
[0014]
The insulating substrate 2 is formed of an electrically insulating material such as a glass epoxy resin in which a glass fiber woven cloth is impregnated with an epoxy resin, or a bismaleimide triazine resin in which a glass fiber woven cloth is impregnated with a bismaleimide triazine resin. For example, in the case of glass epoxy resin, a glass cloth formed by weaving glass fibers made of non-alkali glass vertically and horizontally is impregnated with an epoxy resin precursor and the precursor is semi-cured to form a prepreg. It is manufactured by forming, laminating as necessary, and then heat-curing.
[0015]
The insulating base 2 has an upper surface on which an electronic component such as a semiconductor device is mounted and a connection pad 3 is formed on a mounting portion 2a on which the electronic component such as a semiconductor device is soldered. They are connected via metal bumps made of the like.
[0016]
The connection pads 3 are arranged on the mounting portion 2a of the insulating base 2 so as to correspond one-to-one with the electrodes of the electronic component to be mounted, and are made of a metal material such as copper. A copper foil is thermocompression-bonded on the mounting portion 2a, a copper plating layer is deposited on the surface thereof to a predetermined thickness, and this is etched into a predetermined shape.
[0017]
The connection pad 3 is formed in various shapes such as a circle, an ellipse, a rectangle, and a polygon. In particular, when it is a circle, an electronic component such as a semiconductor device is connected to the upper surface of the connection pad 3 via a metal bump made of solder or the like. When the stress is not concentrated on a specific part of the metal bump, the mechanical strength of the metal bump can be increased. Therefore, the connection pad 3 is preferably circular.
[0018]
When the connection pad 3 has a circular shape, the diameter of the connection pad 3 is the same as or smaller than the diameter of the joint of an electronic component connected to the connection pad 3 via a metal bump. The bonding strength of the metal bump to the connection pad 3 and the electronic component can be made substantially the same, and either the bonding portion of the metal bump and the connection pad 3 of the circuit board or the bonding portion of the metal bump and the electronic component is either The stress is not concentrated, and it is possible to effectively prevent the occurrence of peeling or the like at one of the joints, thereby further improving the long-term reliability.
[0019]
Further, the connection pad 3 has a plating layer (not shown) made of a metal having good conductivity and good solder wettability such as nickel / gold or solder (tin-lead alloy) on the exposed surface. If it is deposited to a thickness of 1 μm to 20 μm by an electroless plating method or the like, the joint connection of the metal bumps to the connection pad 3 can be made easier and more reliable. Therefore, the connection pad 3 is formed by applying an electroplating method or an electroless plating method on the exposed surface of the plating layer made of a metal having good conductivity and good solder wettability such as nickel / gold or solder (tin-lead alloy). It is preferable to deposit the film to a thickness of 1 μm to 20 μm by, for example.
[0020]
The insulating base 2 also has a plurality of via conductors 4 formed from the surface to the inside thereof, and each of the via conductors 4 has a one-to-one correspondence with each connection pad 3. It is connected to the connection pad 3 via.
[0021]
The via conductor 4 serves to electrically connect an electrode of an electronic component connected to the connection pad 3 to an external electric circuit, a wiring layer formed inside the insulating base 2 or the like.
[0022]
The via conductor 4 is made of a metal material such as copper. For example, the via hole is formed by performing drilling or laser processing on the insulating substrate 2, and then using a well-known plating method and etching method to form a via hole. It is formed by adhering to the inner wall with the upper end led out to the upper surface of the insulating base 2.
[0023]
The via conductor 4 is electrically connected to the corresponding connection pad 3 through a lead wire 5.
[0024]
The lead wire 5 is made of a metal such as copper, and is formed on the insulating base 2 so as to connect the via conductor 4 and the corresponding connection pad 3 in the same manner as the connection pad 3.
[0025]
If the via conductor 4 and the lead wire 5 are covered with a resin such as an epoxy resin similar to the resin forming the insulating base 2, the oxidative corrosion of the via conductor 4 and the lead wire 5 can be effectively prevented. Can do. Accordingly, it is preferable that the surfaces of the via conductors 4 and the lead wires 5 are covered with a resin similar to the resin forming the insulating base 2, for example, an epoxy resin.
[0026]
In the present invention, as shown in FIG. 2, the via conductor 4 is perpendicular to the line 6 connecting the via conductor 4 and the corresponding connection pad 3 and the center point of the mounting portion 2a on which the electronic component is mounted. It is important that it is located outside of 7.
[0027]
The via conductor 4 corresponding to each connection pad 3 is perpendicular to the line 6 connecting the connection pad 3 corresponding to the via conductor 4 and the center point of the placement portion 2a on which the electronic component is placed, or in the vertical direction 7, the position where the strength of the metal bump made of solder or the like for connecting the electronic component and the connection pad 3 of the circuit board 1 is the weakest, that is, the connection pad 3 of the circuit board 1 and the lead wire The position of the connecting part with the circuit board 1 is a position deviated from the direction of the stress generated due to the difference in thermal expansion coefficient between the electronic component and the circuit board 1, and as a result, the metal bumps are broken. Is effectively prevented, and the electrical connection between the electronic component and the circuit board 1 can be maintained for a long period of time.
[0028]
Accordingly, the via conductors 4 are more perpendicular to the line 6 connecting the connection pads 3 corresponding to the via conductors 4 and the center point of the placement portion 2a on which the electronic component is placed than the vertical direction 7 or the vertical direction 7 is. It must be located outside.
[0029]
Further, when the width of the lead wire 5 connecting the connection pad 3 and the via conductor 4 is less than 50 μm, the contact portion with the connection pad 3 is reduced and the electrical resistance is increased, and the electrical characteristics of the circuit board 1 are increased. If the thickness exceeds 150 μm, a large amount of metal bumps flow onto the lead-out line 5 and the volume of the metal bumps is likely to be insufficient. Therefore, the width of the lead wire 5 is preferably in the range of 50 μm to 150 μm, and preferably within ½ of the diameter of the corresponding connection pad 3 within the above range.
[0030]
In addition, this invention is not limited to the above-mentioned Example, A various change is possible if it is a range which does not deviate from the summary of this invention.
[0031]
【The invention's effect】
According to the circuit board of the present invention, each via conductor has a connection pad perpendicular to a line connecting the center point of the connection pad corresponding to the via conductor and the center point of the placement portion on which the electronic component is placed. Since the straight line passing through the center point is located on the opposite side of the center point of the mounting portion, the position where the strength of the metal bump connecting the electronic component and the circuit board is the weakest is the insulating base of the electronic component and the circuit board. The position is deviated from the direction of the stress generated due to the difference in thermal expansion coefficient with the insulating base. As a result, the metal bumps are effectively prevented from breaking, and the electrical connection between the electronic component and the circuit board is prevented. It can be maintained over a long period of time.
[Brief description of the drawings]
FIG. 1 is a plan view showing an embodiment of a circuit board according to the present invention.
FIG. 2 is an enlarged view of a main part of the circuit board shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Circuit board 2 ... Insulation base 3 ... Connection pad 4 ... Via conductor 5 ... Lead-out line

Claims

Electronic components have a mounting portion to be mounted on the upper surface, and the thermal expansion coefficient is large insulating substrate than the insulating substrate of the electronic component, throughout the placing portion on the mounting portion of the insulating substrate is arranged, and a plurality of connection pads on which the electronic components of the electrode are connected, the one-to-one correspondence to each connection pad, a plurality of via conductors formed from the surface to the inside of the mounting portion, A circuit board having a plurality of lead lines connecting the connection pads and via conductors, wherein each via conductor is mounted on a center point of the connection pad corresponding to the via conductor and an electronic component is placed. A circuit board characterized by being located on the opposite side of the center point of the mounting part with respect to a straight line passing through the center point of the connection pad perpendicular to the line connecting the center point of the mounting part