JP2004251669A - X-ray inspection system, x-ray inspection method and control program of x-ray inspection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray inspection system, an X-ray inspection method and a control program of the X-ray inspection system, by which an object sample is measured more accurately. <P>SOLUTION: In the X-ray inspection system, a sensitivity correction sample (standard sample) 18 which is made up so as to transmit a prescribed value of X rays, is irradiated with X rays, and intensity of transmission X rays which pass through the sensitivity correction sample 18, is detected by a large number of detecting elements 13c, and correcting gradation data sets corresponding to the intensity of the detected transmission X rays are obtained with respect to the large number of detecting elements 13c, and gradation data of the large number of detecting elements 13c which are obtained with respect to the intensity of the transmission X rays passing through the object sample being irradiated with X rays having prescribed intensity, are corrected based on the correcting gradation data sets. Therefore, the system solves such a problem that conventional systems cannot improve accuracy when measuring small solder bumps because of fluctuations in intensity values obtained from respective detecting elements of an X-ray flat-panel sensor. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

ここで、ＩはＸ線フラットパネルセンサ１３によって検出される透過Ｘ線の強度であり、Ｉ_０はＸ線が対象試料を透過しない場合にＸ線フラットパネルセンサ１３によって検出されるＸ線の強度であり、μ_０は錫のＸ線吸収係数，μ_１は銅のＸ線吸収係数であり、ｔ_０は錫の厚み，ｔ_１は銅の厚みである。また、ｅｘｐの指数部分に相当する値は厚み相当値である。なお、以下では簡単のため各Ｘ線のエネルギーに広がりがあることは無視して説明する。
【００３９】
異なる２つのフォトンエネルギー分布のＸ線についてそれぞれ１，２と番号を付すると、以下の式（２）（３）のように表現することができる。
【数２】

これらの式では、異なるフォトンエネルギーにて同一の対象を測定することを想定しているので、錫と銅の厚みは番号１，２で同一である。
【００４０】
銅のＸ線吸収係数は錫のｋ吸収端の前後でリニアに変化するので、当該ｋ吸収端の直前および直後でほとんど値が変わらない。従って、エネルギーサブトラクション処理においてμ_１１とμ_１２とは同値と考えることができる。一方、錫のＸ線吸収係数は錫のｋ吸収端の前後で大きく変化する。そこで、式（２）（３）のそれぞれについて自然対数をとりその結果同士の差分値を算出すると、以下の式（４）になる。
【数３】

同式（４）の左辺は錫の厚みに比例してその大きさが変化するので、錫の厚み相当値である。また、右辺の値はＸ線の強度によって算出可能な値であるので、上記Ｘ線フラットパネルセンサ１３の各検出素子についてこの値を算出し、各検出素子の輝度値をこの算出値に対応した値にして画像を形成すると、錫の寄与のみを視覚化した画像を得ることができ、半田バンプ３０の良否を判定することができる。
このようにして、測定した輝度値に基づいて対象試料の良否を判定することができる。
【００４１】
（３）感度補正テーブル作成処理：
しかしながら、Ｘ線フラットパネルセンサの各検出素子から取得される輝度値にはばらつきが存在し、このことが小さな半田バンプを測定する際の精度を向上させるうえでの障害となっていた。
本実施形態では、輝度値を検出素子別に補正するための感度補正テーブルを作成し、検出素子に対応する画素別に、感度補正テーブルＴ１を用いて輝度値を補正することにより、輝度値のばらつきをなくし、半田バンプをより精度よく測定することができるようにしている。
【００４２】
以下、図７のフローチャートを参照して、感度補正テーブルＴ１を作成する処理を説明する。ＣＰＵ２５は、メモリ２７に書き込まれた制御プログラム２７ａに従って各部に指示を出し、この処理を実施する。後述する感度補正処理も同様である。
まず、Ｘ−Ｙステージ１５に対象試料を載置していない状態としておいて、メモリ２７の所定領域に設けたカウンタｎを０にリセットする（ステップＳ１０５。以下、「ステップ」の記載を省略）。カウンタｎは、上記感度補正試料「１」〜「３」に対応させる数値を格納しているが、上記ブランクにも数値「４」等を対応させてもよい。次に、カウンタｎを１増加させる（Ｓ１１０）。そして、補正試料制御部２２に対して制御データを出力してサーボモータ１７ｄにより感度補正試料ステージのターンテーブル１７ａを回転させ、ｎ番目の感度補正試料１８をＸ線照射経路Ｃ１に移動させる（Ｓ１１５）。
【００４３】
その後、各種撮影条件を設定する（Ｓ１２０）。ここで、Ｘ線制御部２１に対しては、対象試料を検査するときと同じ所定電流量の管電流をＸ線発生器１１に流す制御データを出力する。次に、Ｘ線を生成させる制御データをＸ線制御部２１に対して出力するとともに、透過Ｘ線の強度を検出させる制御データを画像処理部２４に対して出力することにより、撮影を行う（Ｓ１２５）。
すると、Ｘ線発生器１１は、所定電流量の管電流が流れ、対象試料を検査するときと同じ所定強度のＸ線を生成し、Ｘ線照射経路上にある感度補正試料に照射する。感度補正試料を透過した透過Ｘ線は、Ｘ線フラットパネルセンサ１３に到達し、その強度が多数の検出素子１３ｃ別に電圧信号として検出される。検出された電圧信号は、デジタル変換部１３ｄで各検出素子１３ｃ別に対応する輝度値に変換される。
【００４４】
撮影を行うと、Ｘ線フラットパネルセンサ１３から各検出素子１３ｃ別の補正用階調データである輝度値ｆ（ｘ，ｙ，ｎ）を取得し、図１で示した感度補正テーブルＴ１に格納する（Ｓ１３０）。
図８は、Ｔ１とはどのような意義を有する情報テーブルであるかを模式的に示している。図の上段は、ある一つの検出素子について感度補正試料の厚みと補正前の輝度値との関係を示している。なお、横軸（Ｘ軸）は感度補正試料の厚みの逆数（相対値）であり、縦軸（Ｙ軸）は補正前の輝度値（０〜４０９５の階調値）である。横軸に付したｎ＝１〜３は感度補正試料「１」〜「３」のＸ軸上の位置を示しており、感度補正試料「１」〜「３」に対応する補正前の輝度値をｄ１〜ｄ３としている。ｄ０は、補正後の輝度値の最小値であるが、０とはならず、オフセット値となっている。ｄ４は、補正後の輝度値の最大値である。そして、検出素子の実際の特性を実線で示すとともに、輝度値のオフセットを考慮したうえでの理想的な特性を点線で示している。
【００４５】
同上段に示すように、検出素子は、感度補正試料の逆数に対して直線的な特性とはならず、曲線状の特性となっている。従って、対象試料を精度よく測定するためには、複数の感度補正試料を用いて感度補正テーブルを作成することが望ましい。むろん、直線に近い特性が得られるならば、感度補正試料一つのみを用いて感度補正テーブルを作成してもよい。
【００４６】
図の中段は、ある一つの検出素子に着目したときの感度補正テーブルの内容を模式的に示している。なお、横軸は補正前の輝度値（階調値）であり、縦軸は補正後の輝度値（階調値）である。補正前の輝度値ｄ１〜ｄ３に対応する補正後の輝度値をｄ１’〜ｄ３’としている。補正前の輝度値のオフセット値ｄ０に対応する補正後の輝度値を０としている。これにより、輝度値のオフセットを消去することができる。そして、補正前後の輝度値の対応関係Ｒ１を実線で示すとともに、ｄｎ’＝ｄｎ−ｄ０となる直線を点線で示している。また、図の下段は、感度補正試料の厚みと補正後の輝度値との関係を示している。なお、横軸は感度補正試料の厚みの逆数（相対値）であり、縦軸は補正後の輝度値（階調値）である。
【００４７】
ここで、感度補正試料番号ｎ＝１〜３に対する補正後の輝度値ｄ１’〜ｄ３’は、輝度値のオフセットまでも消去した理想的な特性に一致して直線的な関係となる。すなわち、感度補正テーブルは、輝度値を補正することにより、輝度値の大きさに応じてきめ細やかに輝度値を理想的な感度特性に一致させることができるため、より精度よく対象試料を測定可能とさせる情報テーブルと言うことができる。
また、Ｘ線を完全に遮断した状態での補正前の輝度値に０以外のオフセット値が存在しても、Ｘ線を完全に遮断した状態での補正後の輝度値を０すなわちオフセット値が存在しないようにさせるため、さらに精度よく対象試料を測定可能とさせる情報テーブルと言うことができる。従って、このような感度補正テーブルを用いて輝度値を補正すると、補正前の輝度値のオフセットが消去されるので、さらに補正後の輝度値を理想的な感度特性に一致させ、さらに精度よく対象試料を測定することが可能となる。
【００４８】
さらに、感度補正テーブルは、多数の検出素子別の情報テーブルとされている。
図９は、感度補正テーブルＴ１の構造を模式的に示している。例えば、５７６万画素中の画素１については、感度補正試料「１」、「２」、「３」に相当する基準輝度値１０００，２０００，３０００に対応して、９８０，１９４０，２９４０が格納されていることを示している。なお、各画素は、各検出素子に対応するものである。本Ｘ線検査装置は、輝度値ｆ（ｘ，ｙ，ｎ）を補正前の階調データとし、基準輝度値を補正後の階調データとして、補正前後の階調データを対応させた感度補正テーブルを作成する。従って、本感度補正テーブルは、各画素毎に補正前の輝度値が格納される。例えば、画素１よりも検出感度が５％小さいときには画素２のような輝度値が格納されるし、画素１よりも検出感度が５％大きいときには画素３のような輝度値が格納される。このように、各画素毎に輝度値がばらついているため、より精度よく対象試料を測定することが望まれていたのである。
【００４９】
ここで、感度補正テーブルに格納された各画素と基準輝度値との対応関係から輝度値を補正すると、輝度値のばらつきが無くなり、より精度よく対象試料を測定することが可能となる。また、図８の上段で示した実際の感度特性の曲線が検出素子毎に異なる場合にも、基準輝度値を複数段階設けることによって、輝度値の大きさに応じて適切に輝度値のばらつきを無くすことができ、単に各検出素子別に輝度値を補正する以上に、より精度よく対象試料を測定することが可能となる。
なお、感度補正テーブルに対して基準輝度値別に取得した輝度値を格納する際、カウンタｎと基準輝度値とを対応させた基準輝度値対応テーブルを予めメモリに記憶させておき、同基準輝度値対応テーブルからカウンタｎに対応する基準輝度値を読み出して感度補正テーブルに格納するようにしてもよい。
【００５０】
カウンタｎに相当する感度補正試料を用いて取得された輝度値を感度補正テーブルに格納すると、全ての感度補正試料について撮影を行ったか否かを判断する（Ｓ１３５）。撮影を行っていない感度補正試料が存在する場合には繰り返しＳ１１０〜Ｓ１３５の処理を行い、全感度補正試料を撮影した場合には本フローを終了する。
このようにして、複数の標準試料を順次Ｘ線の照射経路に移動させながら複数の標準試料に所定強度のＸ線を順次照射し、多数の検出素子にて各標準試料を透過した透過Ｘ線の強度を検出し、検出した透過Ｘ線の強度に対応する補正用階調データを同多数の検出素子別かつ同複数の標準試料別に取得することができる。
【００５１】
（４）感度補正処理：
次に、図１０のフローチャートを参照して、感度補正テーブルＴ１を用いて各検出素子別に輝度値を補正する処理を説明する。
まず、Ｘ−Ｙステージ１５に対象試料を載置した状態としておいて、補正試料制御部２２に対して制御データを出力してサーボモータ１７ｄにより感度補正試料ステージのターンテーブル１７ａをブランク１９の位置まで回転させ、感度補正試料１８をＸ線照射経路Ｃ１外に移動させる（Ｓ２０５）。次に、各種撮影条件を設定する（Ｓ２１０）。ここで、Ｘ線制御部２１に対しては、対象試料を検査するときの所定電流量の管電流をＸ線発生器１１に流す制御データを出力する。次に、透過Ｘ線の強度を検出させる制御データを画像処理部２４に対して出力することにより、対象試料を撮影する（Ｓ２１５）。
【００５２】
すると、Ｘ線発生器１１は、所定電流量の管電流が流れ、対象試料を検査するときの所定強度のＸ線を生成し、Ｘ線照射経路上にある対象試料に照射する。対象試料を透過した透過Ｘ線は、Ｘ線フラットパネルセンサ１３に到達し、その強度が多数の検出素子１３ｃ別に電圧信号として検出される。検出された電圧信号は、デジタル変換部１３ｄで各検出素子１３ｃ別に対応する輝度値に変換される。
【００５３】
撮影を行うと、Ｘ線フラットパネルセンサ１３から各検出素子１３ｃ別の補正前の階調データである輝度値ｄ（ｘ，ｙ）を取得し、メモリの所定領域に格納する（Ｓ２２０）。そして、感度補正テーブルを参照して、輝度値ｄ（ｘ，ｙ）に対応する補正後の階調データである輝度値ｄ’（ｘ，ｙ）を取得し、メモリの所定領域に格納して（Ｓ２２５）、本フローを終了する。むろん、各検出素子別に輝度値ｄ（ｘ，ｙ）を取得しながら補正後の輝度値ｄ’（ｘ，ｙ）を算出し、メモリの所定領域に格納するようにしてもよい。
【００５４】
図８の中段は、輝度値を補正する様子をも示している。すなわち、感度補正テーブルに格納された補正前後の輝度値から補正前後の輝度値の対応関係Ｒ１を決定し、補正前の輝度値ｄに対応する補正後の輝度値ｄ’を対応関係Ｒ１から算出することにより、各検出素子別に輝度値を補正することができる。なお、対応関係Ｒ１を表す関係式を、各検出素子毎に、補正前後の輝度値を用いて二次回帰分析により求めてもよいし、補正前の輝度値を横軸として補正後の輝度値を縦軸とした平面において、上述した補正前の輝度値ｄ０〜ｄ４に対応する参照点のうち対象試料の測定結果である輝度値ｄを挟む二つの参照点の座標値から比例配分を行い、補正後の輝度値ｄ’を算出してもよい。
【００５５】
このようにして、補正用階調データと基準階調データとに基づいて、所定強度のＸ線が照射された対象試料を透過した透過Ｘ線の強度に対応して取得される階調データを多数の検出素子別かつ複数段階の基準階調データ別に補正することができる。すると、多数の検出素子から取得される輝度値にばらつきが存在していても、輝度値のばらつきを少なくさせることが可能となる。そして、多数の検出素子別に補正されたばらつきの少ない階調データに基づいて、半田バンプを測定することができる。
なお、上記感度補正テーブル作成処理と感度補正処理を行う本Ｘ線検査装置が、本発明にいう素子別補正手段を構成することになる。
【００５６】
以上説明したように、本発明によると、補正テーブルを参照するという簡易な構成で、多数の検出素子別に補正されたばらつきの少ない階調データを得ることができるので、簡易な構成できめ細やかに対象試料の厚みや大きさ等を測定することができ、対象試料をより精度よく測定することが可能となる。その結果、対象試料の測定データを用いて対象試料の良否を精度よく判定すること等が可能となる。また、階調データは複数段階の基準階調データ別にも補正されるので、この点でさらに精度よく対象試料を測定することが可能となる。従って、補正前の階調データの感度特性が検出素子毎に異なる場合にも、階調データの大きさに応じて適切に階調データのばらつきを無くすことができ、単に各検出素子別に階調データを補正する以上に、より精度よく対象試料を測定することが可能となる。さらに、補正前の階調データに存在するオフセットが補正後に消去されるので、さらに精度よく対象試料を測定することが可能となる。
【００５７】
（５）第二の実施形態：
ところで、Ｘ線発生器のＸ線管１１ａから発生するＸ線の強度Ｉは、以下の式のように、管電流Ｃに比例し、管電圧Ｖの２乗に比例する。
Ｉ＝ＫＶ^２Ｃ …（５）
ただし、Ｋは定数である。
そこで、Ｘ線管の管電流（Ｘ線の強度に比例する）を変化させて撮影して各検出素子の感度特性を取得し、補正してもよい。なお、図８の上段と下段において横軸を管電流の電流量（例えばμＡ単位）と読み替えると、同様の手法により感度補正テーブルを作成して輝度値を補正することができる。
【００５８】
以下、図１１のフローチャートを参照して、第二の実施形態にかかるＸ線検査装置が行う感度補正テーブルを作成する処理を説明する。
なお、Ｘ線検査装置のハードウェアは、第一の実施形態と同じとする。ただし、感度補正試料ステージ１７、感度補正試料（標準試料）１８、補正試料制御部２２については、Ｘ線管の管電流を調整するために用いるが必ずしも必要とするものではない。
まず、Ｘ−Ｙステージ１５に、所定のＸ線透過量とされた厚みが既知の感度補正試料を載置した状態としておいて、メモリ２７の所定領域に設けたカウンタｎを０にリセットする（Ｓ３０５）。次に、カウンタｎを１増加させる（Ｓ３１０）。そして、Ｘ線制御部２１に対して、Ｘ線発生器のＸ線管１１ａに流す管電流をカウンタｎに対応する所定の電流量にする制御データを出力する（Ｓ３１５）。
カウンタｎに対応する管電流の電流量は、例えば図１２の上段に示すようにカウンタｎと管電流の電流量とを対応させた管電流対応テーブルＴ２をメモリ内に記憶させておき、同テーブルＴ２からカウンタｎに対応する電流量を読み出すことにより決定することができる。なお、図に示した管電流対応テーブルＴ２には、管電流の電流量と基準輝度値とを対応させて格納している。ここで、基準輝度値は、輝度値がとりうる範囲内の複数段階の輝度値とされている。
【００５９】
その後、その他の各種撮影条件を設定する（Ｓ３２０）。次に、Ｘ線を生成させる制御データをＸ線制御部２１に対して出力するとともに、透過Ｘ線の強度を検出させる制御データを画像処理部２４に対して出力することにより、撮影を行う（Ｓ３２５）。
すると、Ｘ線発生器１１は、基準階調データに対応する所定電流量の管電流が供給され、所定強度のＸ線を生成し、Ｘ線照射経路上にある感度補正試料（標準試料）に照射する。感度補正試料を透過した透過Ｘ線は、Ｘ線フラットパネルセンサ１３に到達し、その強度が多数の検出素子１３ｃ別に電圧信号として検出される。検出された電圧信号は、デジタル変換部１３ｄで各検出素子１３ｃ別に対応する輝度値に変換される。
【００６０】
撮影を行うと、Ｘ線フラットパネルセンサ１３から各検出素子１３ｃ別の補正用階調データである輝度値ｆ（ｘ，ｙ，ｎ）を取得し、管電流対応テーブルＴ２を参照して、図１２の下段に示す感度補正テーブルＴ３に格納する（Ｓ３３０）。本Ｘ線検査装置は、輝度値ｆ（ｘ，ｙ，ｎ）を補正前の階調データとし、基準輝度値を補正後の階調データとして、補正前後の階調データを対応させた感度補正テーブルＴ３を作成する。
カウンタｎに相当する電流量の管電流をＸ線管１１ａに流して取得された輝度値を感度補正テーブルに格納すると、全段階の電流量の管電流について撮影を行ったか否かを判断する（Ｓ３３５）。撮影を行っていない段階の電流量が存在する場合には繰り返しＳ３１０〜Ｓ３３５の処理を行い、全電流量について撮影した場合には本フローを終了する。
【００６１】
このようにして、基準階調データに対応して異なる電流量とされた複数段階の管電流をＸ線照射手段に順次供給して生成したＸ線を検出素子に照射し、多数の検出素子にてＸ線の強度を検出し、検出したＸ線の強度に対応する補正用階調データを同多数の検出素子別に取得することができる。
作成された感度補正テーブルＴ３を用いて各検出素子別に輝度値を補正する処理は、図１０のフローチャートに従って行うことができる。
なお、本実施形態の感度補正テーブル作成処理と感度補正処理を行う本Ｘ線検査装置が、本発明にいう補正手段と素子別補正手段を構成することになる。
【００６２】
以上説明したように、第二の実施形態でも、第一の実施形態と同じ効果が得られる。すなわち、簡易な構成できめ細やかに対象試料の厚みや大きさ等を測定することができ、対象試料の良否をより精度よく判定することが可能となる。階調データは複数段階の基準階調データ別にも補正されるので、補正前の階調データの感度特性が検出素子毎に異なる場合にも、階調データの大きさに応じて適切に階調データのばらつきを無くすことができ、単に各検出素子別に階調データを補正する以上に、さらに精度よく対象試料を測定することが可能となる。補正前の階調データに存在するオフセットが補正後に消去されるので、さらに精度よく対象試料を測定することが可能となる。
【００６３】
なお、実施形態の５７６万画素の階調データを検出素子（画素）別に補正する処理を実行しても、その処理時間は５秒程度で済むが、感度補正テーブルのデータ量を増やしてテーブル参照のみによって補正処理を実行すれば、さらに処理時間を短縮することができる。例えば、上述した実施形態では感度補正テーブルに対して画素別に基準輝度値に対応した３種類の輝度値を格納したが、画素別に１０種類の輝度値を格納するようにしても、各基準輝度値を３２ビットの浮動小数点で表すとすると２３０メガバイトとなり、この程度の記憶容量を確保するのは容易である。そして、画素別に１０種類の輝度値を格納した感度補正テーブルを参照して５７６万画素の階調データを補正する処理を実行すると、処理時間は２秒程度で済む。
また、検出素子（画素）別に階調データを補正せず、画素に対応する階調データを変化特性等によりまとめて補正するようにしてもよい。この場合であっても、階調データは複数段階の基準階調データ別にも補正されるので、補正前の階調データの感度特性を補正してより精度よく対象試料を測定することが可能となる。
【００６４】
（６）まとめ：
本発明のＸ線検査装置は、その要旨を変更しない範囲で各種の変更が可能であり、上述した実施形態に限られるものではない。
例えば、感度補正テーブルを作成せず、各検出素子別に補正後の輝度値を算出する式を作成して、輝度値を補正するようにしてもよい。同様の効果を得ることができ、対象試料をより精度よく測定することが可能になることに変わりはない。
また、多数の検出素子は、縦横整然と並んだドットマトリクス状以外にも、蜂の巣状等に並んだドットマトリクス状に配置されていてもよい。
以上説明したように、本発明によると、種々の態様により、対象試料をより精度よく測定することが可能なＸ線検査装置およびＸ線検査装置の制御プログラムを提供することができる。また、Ｘ線検査方法としても適用可能である。
【図面の簡単な説明】
【図１】第一の実施形態にかかるＸ線検査装置の概略ブロック図である。
【図２】Ｘ線管の概略構成を示す図である。
【図３】Ｘ線のＸ線フォトンエネルギー分布を示す図である。
【図４】Ｘ線フラットパネルセンサの構成の概略を示すブロック図である。
【図５】試料移動機構の構成の概略を示すブロック図である。
【図６】Ｘ線制御部の構成の概略をＸ線管とともに示すブロック図である。
【図７】感度補正テーブル作成処理を示すフローチャートである。
【図８】感度補正テーブルの意義を模式的に説明する図である。
【図９】感度補正テーブルの構造を模式的に示す図である。
【図１０】感度補正処理を示すフローチャートである。
【図１１】第二の実施形態における感度補正テーブル作成処理を示すフローチャートである。
【図１２】管電流対応テーブルと感度補正テーブルの構造を模式的に示す図である。
【符号の説明】
１０…Ｘ線撮像機構部
１１…Ｘ線発生器
１１ａ…Ｘ線管
１１ｂ…アノード
１１ｃ…カソード
１１ｄ…電子レンズ
１１ｅ…ターゲット
１３…Ｘ線フラットパネルセンサ
１３ａ…シンチレータ
１３ｂ…光検出アレー
１３ｃ…検出素子
１３ｄ…デジタル変換部
１５…Ｘ−Ｙステージ
１７…感度補正試料ステージ
１８…感度補正試料（標準試料）
１９…ブランク
２０…Ｘ線撮像制御部
２１…Ｘ線制御部
２１ａ…管電圧制御回路
２１ｂ…管電流制御回路
２２…補正試料制御部
２３…ステージ制御部
２４…画像処理部
２５…ＣＰＵ
２６ａ…出力部
２６ｂ…入力部
２７…メモリ
２７ａ…制御プログラム
３０…半田バンプ
３１…基板
３２…チップ
Ｃ１…Ｘ線照射経路
Ｔ１，Ｔ３…感度補正テーブル
Ｔ２…管電流対応テーブル[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an X-ray inspection apparatus, an X-ray inspection method, and a control program for an X-ray inspection apparatus that measure a target sample using a large number of detection elements provided in a dot matrix.
[0002]
[Prior art]
Conventionally, this type of X-ray inspection apparatus irradiates a substrate to which electronic components are soldered with X-rays as a target sample, and uses an X-ray detector having a large number of CCD elements provided in a dot matrix form. Is detected for each CCD element. Then, a luminance value, which is gradation data corresponding to the detected intensity of the transmitted X-ray, is acquired for each of a large number of CCD elements, the thickness of the solder and the like are quantified based on the acquired luminance value, and the quality of the target sample is determined. (For example, see Patent Document 1).
[0003]
For example, when the solder is imaged with X-rays having a photon energy distribution having peaks before and after the k-absorption edge of tin, a thickness equivalent value obtained by extracting only the state of tin can be obtained. In addition, solder (an alloy of tin and lead) can be inspected by processing such as generating an image corresponding to the thickness equivalent value.
[0004]
Further, an X-ray flat panel sensor is used as an X-ray detector, and the intensity of transmitted X-rays is detected for each of a large number of detection elements and converted into a digital luminance value.
[0005]
[Patent Document 1]
JP 2000-249532 A
[0006]
[Problems to be solved by the invention]
In the above-described conventional technique, there has been a problem that when the inspection object becomes smaller, the measurement accuracy relatively decreases, and sufficient measurement accuracy cannot be secured. Taking the above solder inspection device as an example, if the size of the solder is several hundred μm, it could be quantified without being greatly affected by the measurement error. The ratio of the error to the error increases, and the measurement error cannot be ignored. In particular, the integration density of ICs in recent years has been rapidly increasing, and accordingly, the BGA (Ball) has been increasing.
The grid bumps are also smaller.
On the other hand, since the luminance value obtained from each detection element of the X-ray flat panel sensor has a variation of about ± 5%, the accuracy in measuring a small solder bump cannot be improved.
[0007]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an X-ray inspection apparatus, an X-ray inspection method, and a control program for an X-ray inspection apparatus capable of measuring a target sample with higher accuracy.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a standard sample having a predetermined X-ray transmission amount is irradiated with X-rays, and the standard sample is detected by a large number of detection elements provided in a dot matrix. The intensity of the transmitted transmitted X-ray is detected, and correction gradation data corresponding to the detected transmitted X-ray intensity is obtained for each of the same number of detection elements. Next, the target sample is irradiated with X-rays of a predetermined intensity, and the intensity of transmitted X-rays transmitted through the target sample is detected by a number of detection elements for each detection element, and gradation data corresponding to the transmitted X-ray intensity is detected. Are obtained for the same number of detection elements. Here, the gradation data acquired for each of the plurality of detection elements is corrected for each detection element by the correction means for each element based on the gradation data for correction. Then, even if there is a variation in the gradation data obtained from many detection elements, it is possible to reduce the variation in the gradation data.
As described above, it is possible to obtain gradation data with little variation corrected for a large number of detection elements, and thus it is possible to accurately measure the target sample. As a result, the quality of the target sample can be accurately determined using the measurement data of the target sample.
[0009]
The target sample may be various ones, for example, a board soldered by BGA, a board soldered by other than BGA, or a board other than the soldered board. Is also good.
Various types of the detection element are conceivable. For example, the detection element may be a silicon element or a non-silicon element. Various configurations can be adopted as the configuration for detecting the intensity of the transmitted X-ray. For example, a configuration in which transmitted X-rays are converted into visible light and received by a silicon element can be employed. In this case, the detection voltage at each silicon element corresponds to the intensity.
Various data such as a luminance value and a lightness value can be considered as the gradation data. Further, various gradation numbers can be set.
[0010]
The element-specific correction means irradiates the standard sample with the X-rays of the predetermined intensity, detects the intensity of the transmitted X-ray transmitted through the standard sample by the plurality of detection elements, and converts the correction gradation data. It may be obtained for each of the same number of detection elements. By irradiating the target sample with X-rays having the intensity to irradiate, it is possible to acquire correction gradation data with a simple configuration.
[0011]
The element-by-element correction means sequentially irradiates the X-rays to a plurality of standard samples having different X-ray transmission amounts corresponding to a plurality of levels of reference gradation data within a range that the gradation data can take, A large number of detection elements detect the intensity of transmitted X-rays transmitted through each standard sample, acquire correction gradation data corresponding to the detected transmitted X-ray intensity for each of the plurality of standard samples, and perform the correction. Based on the gradation data and the reference gradation data, the gradation data obtained corresponding to the intensity of the transmitted X-ray transmitted through the target sample irradiated with the X-rays of the predetermined intensity is referred to as the multi-step reference. A configuration in which correction is performed for each gradation data may be adopted. Then, the gradation data acquired for each of the plurality of detection elements is corrected for each of the plurality of detection elements and for each of a plurality of levels of reference gradation data based on the gradation data for correction and the reference gradation data.
As described above, since the gradation data for many detection elements is corrected for many detection elements and for multiple levels of reference gradation data, if the sensitivity characteristics of the gradation data before correction differ for each detection element, In addition, it is possible to appropriately eliminate the variation of the gradation data according to the size of the gradation data, and it is possible to measure the target sample with higher accuracy than simply correcting the gradation data for each detection element. Become.
[0012]
At this time, the element-specific correction means includes a sample moving mechanism capable of moving any of the plurality of standard samples to the X-ray irradiation path, and sequentially transferring the plurality of standard samples to the X-ray irradiation path. The correction gradation data may be obtained while moving the data to. Then, the gradation data for correction is automatically acquired for each of the plurality of standard samples without performing the operation of manually switching the plurality of standard samples.
[0013]
In addition, any of the X-ray inspection apparatuses described above is provided with X-ray irradiating means capable of irradiating the target sample with X-rays, and a stage on which the target sample can be mounted. The standard sample may be arranged at a position facing the X-ray irradiation direction of the X-ray irradiation unit via the stage, and the standard sample may be arranged between the X-ray irradiation unit and the stage. Then, the gradation data for correction can be reliably obtained, and the gradation data can be corrected.
[0014]
Further, the element-specific correction means includes X-ray irradiating means capable of generating X-rays having an intensity corresponding to the amount of flowing tube current and irradiating the target sample with the X-rays. X-rays generated by sequentially supplying a plurality of stages of tube currents having different current amounts corresponding to the plurality of stages of reference gradation data to the same X-ray irradiating means are radiated to the above-mentioned many detecting elements, , The intensity of the X-ray is detected, the correction gradation data corresponding to the detected X-ray intensity is obtained, and the X-ray of the predetermined intensity is irradiated based on the correction gradation data. The gradation data acquired corresponding to the intensity of the transmitted X-ray transmitted through the sample may be corrected for each of the above-mentioned many detection elements by the correction means for each element. Also in this case, the gradation data obtained for each of the many detection elements is corrected for each of the many detection elements and for each of a plurality of levels of reference gradation data based on the correction gradation data and the reference gradation data.
[0015]
Here, the element-by-element correcting means sets the correction gradation data as the pre-correction gradation data, and uses the reference gradation data as the post-correction gradation data to correspond to the gradation data before and after the correction. A table is created, and the gradation data before correction corresponding to the intensity of the transmitted X-ray transmitted through the target sample irradiated with the X-rays of the predetermined intensity is obtained, and the gradation table before the correction is obtained by referring to the correction table. The configuration may be such that the corrected gradation data corresponding to the gradation data is acquired. The gradation data can be corrected with a simple configuration that refers to the correction table.
If there is an offset value other than 0 in the gradation data before correction in a state where X-rays are completely blocked, the element-specific correction unit performs the correction after the correction in a state where X-rays are completely blocked. The above-described correction table may be created so that the gradation data is 0, that is, there is no offset value. That is, since the offset of the gradation data before the correction is deleted, the gradation data after the correction is further matched with the ideal sensitivity characteristic, and the target sample can be measured more accurately.
[0016]
The case where the present invention is realized as an apparatus has been described above, but the present invention is also applicable to a method for realizing such an apparatus. Therefore, the present invention is also effective as a control method for an X-ray inspection apparatus, and basically the same effects are obtained in the inventions according to claims 8 and 9. The idea of the invention is that such an X-ray inspection apparatus may be realized alone, applied to a certain method, or used in a state where the method is incorporated in another device. The invention is not limited to this, but includes various aspects. Therefore, it can be changed as appropriate, such as software or hardware.
[0017]
As an embodiment of the idea of the present invention, the present invention is also applicable to software for controlling the above method. Therefore, the present invention is also effective as a control program for an X-ray inspection apparatus, and the invention according to claims 10 and 11 has basically the same operation. Further, a medium on which the program is recorded may be distributed, and the program may be read from the recording medium into a computer as appropriate. That is, the present invention can be applied as a computer-readable recording medium on which the program is recorded, and basically has the same operation.
Needless to say, the configurations described in claims 2 to 4, 6, and 7 can be associated with the method, the program, and the medium on which the program is recorded. Further, the recording medium may be any recording medium to be developed in the future, in addition to a magnetic recording medium and a magneto-optical recording medium. The duplication stage of the primary duplicated product, the secondary duplicated product, etc. does not matter. The scope of the present invention includes a case in which a part is realized by hardware, and a form in which a part is recorded on a recording medium and read as needed as needed.
[0018]
【The invention's effect】
As described above, according to the first, fifth, and eighth to eleventh aspects of the present invention, the target sample can be measured with higher accuracy.
According to the second and sixth aspects of the present invention, the target sample is measured based on the gradation data corrected for each of a large number of detection elements and for each of a plurality of levels of reference gradation data. Can be measured. Further, even when the sensitivity characteristics of the gradation data before correction differ from one detection element to another, it is possible to appropriately eliminate the variation in the gradation data according to the size of the gradation data. It is possible to more accurately measure the target sample than to correct the data.
[0019]
According to the third aspect of the present invention, since the correction gradation data is automatically obtained, the convenience can be improved.
According to the invention according to claim 4, it is possible to reliably measure the target sample with higher accuracy.
According to the invention according to claim 7, it is possible to measure the target sample with a simple configuration with higher accuracy.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Here, embodiments of the present invention will be described in the following order.
(1) Configuration of X-ray inspection apparatus:
(2) Energy subtraction processing:
(3) Sensitivity correction table creation processing:
(4) Sensitivity correction processing:
(5) Second embodiment:
(6) Summary:
[0021]
(1) Configuration of X-ray inspection apparatus:
FIG. 1 is a block diagram schematically showing the configuration of the X-ray inspection apparatus according to the first embodiment of the present invention. The present apparatus includes an X-ray imaging mechanism unit 10 and an X-ray imaging control unit 20. The X-ray imaging mechanism unit 10 includes an X-ray generator (X-ray irradiating unit) 11, an X-ray flat panel sensor (X-ray detector) 13, an XY stage (a stage on which a target sample can be placed) 15, a sensitivity. A correction sample stage 17 is provided. The X-ray imaging control unit 20 includes an X-ray control unit 21, a correction sample control unit 22, a stage control unit 23, an image processing unit 24, a CPU 25, an output unit 26a, an input unit 26b, and a memory 27.
[0022]
The memory 27 includes a ROM and a RAM. The control program 27a and default data of the X-ray inspection apparatus of the present invention are recorded in the ROM in advance, and a sensitivity correction table (correction table) generated when performing the X-ray inspection. T1 and other data are recorded in the RAM. Of course, a part of the memory may be replaced with a hard disk.
The X-ray control unit 21 can control the X-ray generator 11 to cause the X-ray generator 11 to generate X-rays. As will be described in detail later, the amount of tube current flowing through the X-ray generator 11 is controlled by acquiring the applied voltage, the imaging time, and the like for the X-ray tube with reference to the imaging condition data recorded as the default data. The X-ray generator 11 is controlled so as to be driven under predetermined imaging conditions. In order to perform the energy subtraction processing, X-rays are generated under two different imaging conditions.
[0023]
The correction sample control unit 22 is connected to the sensitivity correction sample stage 17, and moves any one of the plurality of sensitivity correction samples (standard samples) 18 or blanks (no sensitivity correction samples) 19 to a predetermined X-ray irradiation path C1. Is performed. The correction sample control unit 22 and the sensitivity correction sample stage 17 constitute a sample moving mechanism capable of moving any one of the plurality of standard samples to the X-ray irradiation path.
The stage control unit 23 is connected to the XY stage 15 and performs control to move the XY stage 15 in the horizontal X and Y2 directions. The XY stage 15 can be moved to mount the soldered substrate 31 as a target sample and measure the thickness of the solder and the like. The stage control unit 23 acquires the target sample measurement position coordinate data from the memory 27, and moves the XY stage 15 to the coordinates indicated by the data.
[0024]
The image processing unit 24 is connected to the X-ray flat panel sensor 13 and adjusts a luminance value (gradation data) corresponding to the intensity of the transmitted X-ray transmitted through the target sample or the transmitted X-ray transmitted through the standard sample. Obtained from the sensor 13. The same luminance values are stored in the memory 27 as sequential data (each I ₁ , I ₂ , I _1sta , I _2sta ). The numbers 1 and 2 assigned to the measurement data based on the detection value of the X-ray flat panel sensor 13 correspond to the above two imaging conditions.
[0025]
The output unit 26a is a display for displaying a processing result or the like in the CPU 25, and the input unit 26b is an operation input device for receiving a user's input. Of course, the output unit 26a may be a printer or an audio output device. The user can perform various operation inputs through the input unit 26b, and confirm various calculation results and measurement data obtained by the processing of the CPU 25, the results of the solder bump quality determination, and the like from the output unit 26a. Can be. The CPU 25 can execute predetermined arithmetic processing according to the control program 27a stored in the memory 27. When the CPU 25 receives an operation input such as an inspection instruction from a user through the input unit 26b or the like, the CPU 25 executes the control program 27a and Measure.
[0026]
The X-ray generator 11 applies a voltage to the X-ray tube under the control of the X-ray control unit 21 to flow a tube current, and generates X-rays having an intensity corresponding to the amount of the flowing tube current. Then, X-rays are emitted toward the stage 15 for the designated time. By setting the voltage applied to the X-ray tube, the amount of tube current flowing through the X-ray tube, and the X-ray irradiation time under predetermined conditions, the target sample can be irradiated with X-rays of a predetermined intensity.
As shown in FIG. 2, the X-ray tube 11a includes an anode 11b, a cathode 11c, an electron lens 11d, and a target 11e. Electrons that fly out of the cathode 11c due to the voltage applied to the X-ray tube 11a travel in the direction of the anode 11b, are squeezed by the electron lens 11d composed of a coil, and collide with a minute position of the target 11e.
[0027]
When the electrons collide with the target 11e, the electrons in the target 11e are excited, and the energy at which the excited electrons transition to the low-level orbit is emitted as X-rays. A shutter (not shown) is provided at a predetermined position of the X-ray tube 11a, and when irradiating the X-ray to the outside of the X-ray tube 11a, the shutter opens to form an opening, and the X-ray passes through the opening. Proceed outside. At this time, the X-rays are emitted while spreading in a direction substantially perpendicular to the traveling direction, that is, in a substantially conical shape with the opening at the top. When the target sample is mounted on the stage 15, the X-ray generator 11 irradiates the target sample with X-rays.
[0028]
FIG. 3 is a diagram showing an X-ray photon energy distribution of X-rays emitted from the opening at each applied voltage (30, 40, 50 kV) to the X-ray tube 11a. The X-ray intensity is represented by the number of X-ray photons per unit time (cps; counts per second) or the like. In the figure, the vertical axis represents relative X-ray intensity, and the horizontal axis represents X-ray photon energy. Is shown. The X-rays emitted from the X-ray tube 11a have different photon energies giving peaks depending on the applied voltage and have a broader photon energy distribution. Therefore, by changing the applied voltage, it is possible to generate X-rays having different photon energies and photon energy distributions that give intensity peaks. In this embodiment, tin has intensity peaks before and after the k absorption edge (29.4 keV) of tin. An energy subtraction process is performed using X-rays having different photon energy distributions. That is, the imaging condition data is setting data for irradiating X-rays having such two different photon energy distributions.
[0029]
An X-Y stage 15 and an X-ray flat panel sensor 13 are arranged in the X-ray irradiation direction from the X-ray generator 11. The XY stage 15 can mount a substrate 31 on which a chip 32 having a plurality of solder bumps 30 serving as a sample to be inspected is mounted, and in a state substantially perpendicular to the X-ray irradiation direction with the substrate 31 mounted. Can be moved to The position of the stage 15 is accurately controlled by an arbitrary coordinate value specified by the stage control unit 23.
[0030]
FIG. 4 is a block diagram schematically showing the configuration of the X-ray flat panel sensor 13. A scintillator 13a, which is a fluorescent substance, is provided below the sensor 13, and converts transmitted X-rays transmitted through the target sample into visible light. On the scintillator 13a, a light detection array 13b having a large number of detection elements 13c provided in a dot matrix is provided. The many detection elements 13c are arranged above the XY stage 15 at positions facing the X-ray irradiation direction of the X-ray generator 11 via the XY stage 15.
The large number of detecting elements 13c can be, for example, amorphous silicon light receiving elements formed on one surface of the substrate of the light detecting array. Further, the number of the detection elements 13c arranged in the dot matrix can be various numbers. In the present embodiment, it is assumed that the number of detection elements 13c is 2,400 (horizontal) × 2,400 (vertical), that is, 5.76 million. The light detection array 13b detects the intensity of the transmitted X-ray transmitted through the target sample for each of the many detection elements 13c, and outputs a voltage corresponding to the intensity of the transmitted X-ray.
[0031]
A digital conversion unit 13d is connected to the light detection array 13b. The digital conversion unit 13d converts the voltage detected by the light detection array 13b into a digital luminance value for each detection element 13c, and outputs the digital luminance value to the image processing unit 24. In the present embodiment, the output luminance value is described as being 12 bits representing 0 to 4095, but the number of gradations of the luminance value may be various other than 4096.
In this manner, the X-ray flat panel sensor 13 detects the intensity of the transmitted X-ray transmitted through the target sample by the plurality of detection elements 13c for each of the detection elements 13c, and determines the gradation corresponding to the detected intensity of the transmitted X-ray. Data is output for each of the many detection elements 13c. Then, the image processing unit 24 measures the luminance value, which is the output gradation data, for each of the many detection elements 13c. Note that each pixel of the minimum unit in which the image processing unit 24 performs image processing based on the luminance value corresponds to each detection element 13c.
[0032]
The sensitivity correction sample stage 17 is disposed above the X-ray generator 11 and between the X-ray generator 11 and the XY stage 15.
FIG. 5 is a block diagram schematically showing the configuration of the sample moving mechanism. The sensitivity correction sample stage 17 includes a disk-shaped turntable 17a having a substantially horizontal portion for holding the sensitivity correction sample 18, and a servomotor 17b. The turntable 17a is provided with four openings, three of which are provided with the sensitivity correction sample 18, and the other one is left blank with nothing attached. Therefore, the sensitivity correction sample 18 is disposed between the X-ray generator 11 and the XY stage 15. With this arrangement, it is possible to reliably measure the target sample with higher accuracy. Of course, the sensitivity correction sample may be placed on the XY stage 15, or the sensitivity correction sample may be arranged between the XY stage 15 and the X-ray flat panel sensor 13. .
The servomotor 17d rotationally drives the turntable 17a under the control of the correction sample control unit 22 to move any of the four openings to the X-ray irradiation path.
According to the above configuration, a correction luminance value (correction gradation data) is automatically acquired for each of the plurality of sensitivity correction samples without performing an operation of manually switching the plurality of sensitivity correction samples. , Convenience is improved.
[0033]
Of course, instead of the turntable, the sensitivity correction sample stage may be configured using a horizontal table that can move linearly horizontally. In this case, the same effect can be obtained.
The sensitivity correction sample 18 is formed by forming a predetermined X-ray absorbing substance (for example, lead) having a known thickness into a substantially disk shape. Therefore, the sensitivity correction sample 18 has a predetermined X-ray transmission amount.
[0034]
The lower part of the figure shows the correspondence between each sensitivity-corrected sample, the shape, and the reference luminance value (reference gradation data). Here, the reference luminance value refers to a reference value of the luminance value when the sensitivity correction sample is irradiated with X-rays of a predetermined intensity, and it is assumed that there is no variation in the detection sensitivity of each detection element of the X-ray flat panel sensor 13. Means the ideal luminance value output by the sensor 13. The reference luminance value is provided in a plurality of levels (three levels in the example in the drawing) within a range in which the output luminance value can take.
The correspondence shown in the figure indicates that the sensitivity correction sample becomes thinner as 1, 2, and 3 become smaller, and the reference luminance value becomes larger. When a sensitivity correction sample is present, X-rays are absorbed, and the thicker the sensitivity correction sample, the smaller the amount of X-rays transmitted therethrough, so that the output luminance value of the X-ray flat panel sensor decreases. Therefore, the reference luminance value is large for the lightest sensitivity correction sample “3”, and is smallest for the thickest sensitivity correction sample “1”. As described above, the plurality of sensitivity correction samples 18 have different X-ray transmission amounts corresponding to the reference luminance values in a plurality of steps within a range in which the luminance value can be obtained. Then, as shown in FIG. 1, a sensitivity correction table T1 in which the reference luminance value is associated with the luminance value f (x, y, n) for each detection element 13c is created. Here, (x, y) is the coordinate value of the detection element, and n is the number of the sensitivity-corrected sample.
In the present embodiment, sensitivity correction samples (samples having different thicknesses) are photographed to acquire and correct the sensitivity characteristics of each detection element.
[0035]
As shown in FIG. 6, the X-ray controller 21 includes a tube voltage control circuit 21a and a tube current control circuit 21b for irradiating the sensitivity correction sample and the target sample with X-rays of a desired intensity. Both circuits 21a and 21b are known circuits. When controlling the tube voltage, the tube voltage control circuit 21a divides the tube voltage applied to the cathode 11c into several volts by a series circuit of resistance elements, and divides the tube voltage with a reference voltage from a known reference voltage generation circuit. Is input to a comparison circuit to perform feedback control. When controlling the tube current, the tube current control circuit 21b converts the tube current flowing through the X-ray tube 11a into a voltage of about several volts by the resistance element r1, and this voltage and a reference from a known reference voltage generation circuit. The feedback control is performed by inputting the voltage to the comparison circuit. Here, if the amount of the filament current flowing to the cathode 11c changes due to, for example, the conduction angle control of the thyristor, the amount of the thermoelectrons generated from the cathode 11c also changes, and the amount of the tube current flowing from the target 11e to the cathode 11c changes.
[0036]
(2) Energy subtraction processing:
Next, the energy subtraction processing will be described. The X-ray absorption coefficient of each element has a dependency on the photon energy. Looking at the X-ray absorption coefficient with respect to the X-ray photon energy, the k-absorption end of the X-ray absorption coefficient of tin (Sn) included in the solder bump 30 is 29.4 keV, whereas copper (Cu: printed wiring) is used. X-ray absorption coefficient changes substantially linearly around the 29.4 keV. Then, the target sample is irradiated with X-rays having different photon energy distributions having strong intensity peaks before and after the k absorption edge, and when each transmitted X-ray is detected, two photon energy distributions are obtained for the X-rays transmitted through copper. , There is almost no difference in the detection intensity, but in the case of tin, a large difference occurs.
[0037]
By utilizing this difference, it is possible to calculate the thickness equivalent value while extracting the contribution of tin while eliminating the contribution of copper. The X-ray absorption coefficient of silicon, which is the main component of the chip mounted on the substrate, also changes linearly around the k-absorption edge of tin, so that the contribution of silicon can be eliminated. Here, for the sake of simplicity, the description will be made by limiting the material that transmits X-rays to tin and copper. However, even if other elements are contained, the absorption edges of the other elements are located before and after the k absorption edge of tin. As long as it does not exist, the contribution can be eliminated by the same processing.
[0038]
Generally, the intensity of an X-ray transmitted through a substance can be expressed by the following equation (1).
(Equation 1)

Here, I is the intensity of the transmitted X-ray detected by the X-ray flat panel sensor 13, and I ₀ Is the intensity of the X-ray detected by the X-ray flat panel sensor 13 when the X-ray does not pass through the target sample, and μ ₀ Is the X-ray absorption coefficient of tin, μ ₁ Is the X-ray absorption coefficient of copper, t ₀ Is the thickness of tin, t ₁ Is the thickness of the copper. The value corresponding to the exponent part of exp is the thickness equivalent value. In the following, for the sake of simplicity, the explanation will be made ignoring that the energy of each X-ray has a spread.
[0039]
By assigning numbers 1 and 2 to X-rays having two different photon energy distributions, the X-rays can be expressed as the following equations (2) and (3).
(Equation 2)

In these formulas, it is assumed that the same object is measured with different photon energies, and therefore, the thicknesses of tin and copper are the same for the numbers 1 and 2.
[0040]
Since the X-ray absorption coefficient of copper changes linearly before and after the k-absorption edge of tin, the value hardly changes immediately before and immediately after the k-absorption edge. Therefore, in the energy subtraction process, μ ₁₁ And μ ₁₂ Can be considered equivalent. On the other hand, the X-ray absorption coefficient of tin changes significantly before and after the k-absorption edge of tin. Therefore, when a natural logarithm is calculated for each of the expressions (2) and (3) and a difference value between the results is calculated, the following expression (4) is obtained.
[Equation 3]

Since the size of the left side of the equation (4) changes in proportion to the thickness of tin, it is a value corresponding to the thickness of tin. Since the value on the right side is a value that can be calculated based on the intensity of X-rays, this value was calculated for each detection element of the X-ray flat panel sensor 13, and the luminance value of each detection element was associated with this calculated value. When an image is formed with a value, an image in which only the contribution of tin is visualized can be obtained, and the quality of the solder bump 30 can be determined.
In this way, the quality of the target sample can be determined based on the measured luminance value.
[0041]
(3) Sensitivity correction table creation processing:
However, there are variations in the luminance values obtained from the respective detection elements of the X-ray flat panel sensor, and this has been an obstacle in improving the accuracy in measuring small solder bumps.
In the present embodiment, a sensitivity correction table for correcting the luminance value for each detection element is created, and the luminance value is corrected for each pixel corresponding to the detection element using the sensitivity correction table T1, thereby reducing the variation in the luminance value. This eliminates the need for more accurate measurement of solder bumps.
[0042]
Hereinafter, the process of creating the sensitivity correction table T1 will be described with reference to the flowchart of FIG. The CPU 25 issues instructions to each unit according to the control program 27a written in the memory 27, and performs this processing. The same applies to the sensitivity correction processing described later.
First, while the target sample is not placed on the XY stage 15, the counter n provided in a predetermined area of the memory 27 is reset to 0 (step S105; hereinafter, the description of "step" is omitted). . The counter n stores numerical values corresponding to the sensitivity correction samples “1” to “3”. However, the numerical value “4” may correspond to the blank. Next, the counter n is incremented by 1 (S110). Then, control data is output to the correction sample control unit 22, the turn table 17a of the sensitivity correction sample stage is rotated by the servo motor 17d, and the nth sensitivity correction sample 18 is moved to the X-ray irradiation path C1 (S115). ).
[0043]
Thereafter, various photographing conditions are set (S120). Here, control data for causing the X-ray generator 11 to pass a tube current having a predetermined current amount to the X-ray generator 11 is output to the X-ray control unit 21. Next, imaging is performed by outputting control data for generating X-rays to the X-ray control unit 21 and outputting control data for detecting the intensity of transmitted X-rays to the image processing unit 24 ( S125).
Then, the X-ray generator 11 causes a tube current of a predetermined current amount to flow, generates X-rays having the same predetermined intensity as when inspecting the target sample, and irradiates the sensitivity-corrected sample on the X-ray irradiation path. The transmitted X-ray that has passed through the sensitivity correction sample reaches the X-ray flat panel sensor 13, and its intensity is detected as a voltage signal for each of the many detection elements 13c. The detected voltage signal is converted into a luminance value corresponding to each detection element 13c by the digital conversion unit 13d.
[0044]
When imaging is performed, a luminance value f (x, y, n), which is gradation data for correction for each detection element 13c, is acquired from the X-ray flat panel sensor 13 and stored in the sensitivity correction table T1 shown in FIG. (S130).
FIG. 8 schematically shows what significance T1 is for an information table. The upper part of the drawing shows the relationship between the thickness of the sensitivity-corrected sample and the luminance value before correction for one detection element. The horizontal axis (X-axis) is the reciprocal (relative value) of the thickness of the sensitivity-corrected sample, and the vertical axis (Y-axis) is the luminance value before correction (gradation value from 0 to 4095). N = 1 to 3 on the horizontal axis indicate the positions on the X axis of the sensitivity correction samples “1” to “3”, and the luminance values before correction corresponding to the sensitivity correction samples “1” to “3” Are d1 to d3. d0 is the minimum value of the corrected luminance value, but does not become 0, and is an offset value. d4 is the maximum value of the corrected luminance value. The actual characteristics of the detection element are indicated by solid lines, and the ideal characteristics in consideration of the offset of the luminance value are indicated by dotted lines.
[0045]
As shown in the upper row, the detection element does not have a linear characteristic with respect to the reciprocal of the sensitivity correction sample, but has a curved characteristic. Therefore, in order to accurately measure a target sample, it is desirable to create a sensitivity correction table using a plurality of sensitivity correction samples. Of course, if characteristics close to a straight line can be obtained, a sensitivity correction table may be created using only one sensitivity correction sample.
[0046]
The middle part of the figure schematically shows the contents of the sensitivity correction table when focusing on one certain detection element. Note that the horizontal axis is the luminance value (gradation value) before correction, and the vertical axis is the luminance value (gradation value) after correction. The luminance values after correction corresponding to the luminance values d1 to d3 before correction are d1 'to d3'. The luminance value after correction corresponding to the offset value d0 of the luminance value before correction is set to 0. This makes it possible to eliminate the offset of the luminance value. Then, the correspondence R1 between the luminance values before and after the correction is indicated by a solid line, and the straight line where dn '= dn-d0 is indicated by a dotted line. The lower part of the figure shows the relationship between the thickness of the sensitivity-corrected sample and the corrected luminance value. Note that the horizontal axis is the reciprocal (relative value) of the thickness of the sensitivity correction sample, and the vertical axis is the corrected luminance value (gradation value).
[0047]
Here, the corrected luminance values d1 ′ to d3 ′ for the sensitivity correction sample numbers n = 1 to 3 have a linear relationship in accordance with the ideal characteristic in which even the offset of the luminance value has been deleted. In other words, since the sensitivity correction table corrects the luminance value, the luminance value can be precisely and precisely matched to the ideal sensitivity characteristic according to the magnitude of the luminance value, so that the target sample can be measured more accurately. Information table.
Further, even if there is an offset value other than 0 in the luminance value before correction in the state where X-rays are completely blocked, the luminance value after correction in the state where X-rays are completely blocked is 0, that is, the offset value is This information table can be referred to as an information table that allows the target sample to be measured with higher accuracy so that the target sample does not exist. Therefore, when the luminance value is corrected using such a sensitivity correction table, the offset of the luminance value before correction is deleted, so that the corrected luminance value matches the ideal sensitivity characteristic, and the target value is more accurately corrected. The sample can be measured.
[0048]
Further, the sensitivity correction table is an information table for each of a large number of detection elements.
FIG. 9 schematically shows the structure of the sensitivity correction table T1. For example, for pixel 1 out of 5.76 million pixels, 980, 1940, and 2940 are stored corresponding to reference luminance values 1000, 2000, and 3000 corresponding to the sensitivity correction samples “1”, “2”, and “3”. It indicates that. Each pixel corresponds to each detection element. This X-ray inspection apparatus performs sensitivity correction in which the luminance value f (x, y, n) is used as gradation data before correction, and the reference luminance value is used as gradation data after correction. Create a table. Therefore, in this sensitivity correction table, the luminance value before correction is stored for each pixel. For example, when the detection sensitivity is 5% lower than the pixel 1, a luminance value like the pixel 2 is stored. When the detection sensitivity is 5% higher than the pixel 1, a luminance value like the pixel 3 is stored. As described above, since the luminance value varies for each pixel, it has been desired to measure the target sample with higher accuracy.
[0049]
Here, when the luminance value is corrected based on the correspondence between each pixel stored in the sensitivity correction table and the reference luminance value, there is no variation in the luminance value, and the target sample can be measured more accurately. Further, even when the actual sensitivity characteristic curve shown in the upper part of FIG. 8 differs for each detection element, by providing a plurality of levels of the reference luminance value, the variation of the luminance value can be appropriately adjusted according to the magnitude of the luminance value. This makes it possible to measure the target sample with higher accuracy than simply correcting the luminance value for each detection element.
When storing the brightness values acquired for each reference brightness value in the sensitivity correction table, a reference brightness value correspondence table in which the counter n and the reference brightness value are associated is stored in a memory in advance, and the reference brightness value is stored. The reference luminance value corresponding to the counter n may be read from the correspondence table and stored in the sensitivity correction table.
[0050]
When the brightness value obtained using the sensitivity correction sample corresponding to the counter n is stored in the sensitivity correction table, it is determined whether or not the photographing has been performed for all the sensitivity correction samples (S135). If there is a sensitivity-corrected sample for which no imaging has been performed, the processing in steps S110 to S135 is repeatedly performed. If all the sensitivity-corrected samples have been imaged, this flow ends.
In this manner, a plurality of standard samples are sequentially irradiated with X-rays of a predetermined intensity while sequentially moving the plurality of standard samples to an X-ray irradiation path, and transmitted X-rays transmitted through each standard sample by a large number of detection elements. , And correction gradation data corresponding to the detected transmitted X-ray intensity can be obtained for the same number of detection elements and for the same plurality of standard samples.
[0051]
(4) Sensitivity correction processing:
Next, a process of correcting the luminance value for each detection element using the sensitivity correction table T1 will be described with reference to the flowchart of FIG.
First, with the target sample placed on the XY stage 15, control data is output to the correction sample control unit 22, and the turntable 17a of the sensitivity correction sample stage is moved to the position of the blank 19 by the servomotor 17d. To move the sensitivity-corrected sample 18 out of the X-ray irradiation path C1 (S205). Next, various photographing conditions are set (S210). Here, control data for causing the X-ray generator 11 to pass a predetermined amount of tube current when inspecting the target sample to the X-ray control unit 21 is output. Next, by outputting control data for detecting the intensity of the transmitted X-ray to the image processing unit 24, the target sample is photographed (S215).
[0052]
Then, the X-ray generator 11 causes a predetermined amount of tube current to flow, generates X-rays of a predetermined intensity when inspecting the target sample, and irradiates the target sample on the X-ray irradiation path. The transmitted X-ray that has passed through the target sample reaches the X-ray flat panel sensor 13, and its intensity is detected as a voltage signal for each of the many detection elements 13c. The detected voltage signal is converted into a luminance value corresponding to each detection element 13c by the digital conversion unit 13d.
[0053]
When imaging is performed, a luminance value d (x, y), which is gradation data before correction for each detection element 13c, is acquired from the X-ray flat panel sensor 13 and stored in a predetermined area of the memory (S220). Then, by referring to the sensitivity correction table, a luminance value d ′ (x, y), which is the corrected gradation data corresponding to the luminance value d (x, y), is acquired and stored in a predetermined area of the memory. (S225), this flow ends. Of course, the corrected luminance value d '(x, y) may be calculated while acquiring the luminance value d (x, y) for each detection element, and may be stored in a predetermined area of the memory.
[0054]
The middle part of FIG. 8 also shows how the luminance value is corrected. That is, the correspondence R1 between the luminance values before and after the correction is determined from the luminance values before and after the correction stored in the sensitivity correction table, and the corrected luminance value d 'corresponding to the luminance value d before the correction is calculated from the correspondence R1. By doing so, the luminance value can be corrected for each detection element. Note that a relational expression representing the correspondence R1 may be obtained for each detection element by a secondary regression analysis using the luminance values before and after the correction, or the luminance value after the correction using the luminance value before the correction as the horizontal axis. In the plane having the vertical axis as the vertical axis, the proportional distribution is performed from the coordinate values of two reference points sandwiching the luminance value d that is the measurement result of the target sample among the reference points corresponding to the luminance values d0 to d4 before correction described above, The corrected luminance value d ′ may be calculated.
[0055]
In this manner, based on the correction gradation data and the reference gradation data, the gradation data obtained corresponding to the intensity of the transmitted X-ray transmitted through the target sample irradiated with the X-ray of the predetermined intensity is obtained. Correction can be made for a large number of detection elements and for a plurality of levels of reference gradation data. Then, even if there are variations in luminance values obtained from a large number of detection elements, it is possible to reduce variations in luminance values. Then, the solder bumps can be measured based on the gradation data with little variation corrected for a large number of detection elements.
The X-ray inspection apparatus that performs the above-described sensitivity correction table creation processing and sensitivity correction processing constitutes the element-by-element correction means according to the present invention.
[0056]
As described above, according to the present invention, with a simple configuration of referring to the correction table, it is possible to obtain gradation data with little variation corrected for a large number of detection elements. The thickness, size, and the like of the target sample can be measured, and the target sample can be measured with higher accuracy. As a result, the quality of the target sample can be accurately determined using the measurement data of the target sample. Further, since the gradation data is also corrected for each of a plurality of levels of reference gradation data, it is possible to measure the target sample with higher accuracy in this respect. Therefore, even when the sensitivity characteristics of the gradation data before correction differ for each detection element, it is possible to appropriately eliminate the variation in the gradation data according to the size of the gradation data. It is possible to more accurately measure the target sample than to correct the data. Further, since the offset existing in the gradation data before correction is deleted after the correction, the target sample can be measured with higher accuracy.
[0057]
(5) Second embodiment:
By the way, the intensity I of the X-rays generated from the X-ray tube 11a of the X-ray generator is proportional to the tube current C and proportional to the square of the tube voltage V as in the following equation.
I = KV ² C ... (5)
Here, K is a constant.
Therefore, the sensitivity characteristic of each detection element may be acquired by changing the tube current of the X-ray tube (proportional to the X-ray intensity) to obtain and correct the sensitivity characteristics. When the horizontal axis is read as the current of the tube current (for example, in μA unit) in the upper and lower parts of FIG. 8, a sensitivity correction table can be created by the same method to correct the luminance value.
[0058]
Hereinafter, a process of creating a sensitivity correction table performed by the X-ray inspection apparatus according to the second embodiment will be described with reference to a flowchart of FIG.
Note that the hardware of the X-ray inspection apparatus is the same as in the first embodiment. However, the sensitivity correction sample stage 17, the sensitivity correction sample (standard sample) 18, and the correction sample control unit 22 are used for adjusting the tube current of the X-ray tube, but are not necessarily required.
First, a counter n provided in a predetermined area of the memory 27 is reset to 0 while a sensitivity correction sample having a predetermined X-ray transmission amount and a known thickness is placed on the XY stage 15 ( S305). Next, the counter n is incremented by 1 (S310). Then, control data is output to the X-ray controller 21 so that the tube current flowing through the X-ray tube 11a of the X-ray generator becomes a predetermined current amount corresponding to the counter n (S315).
The current amount of the tube current corresponding to the counter n is stored in a memory, for example, as shown in the upper part of FIG. 12, by storing a tube current correspondence table T2 in which the counter n corresponds to the current amount of the tube current in the memory. It can be determined by reading the current amount corresponding to the counter n from T2. In the tube current correspondence table T2 shown in the figure, the current amount of the tube current and the reference luminance value are stored in association with each other. Here, the reference luminance value is a luminance value in a plurality of steps within a range that the luminance value can take.
[0059]
Thereafter, other various photographing conditions are set (S320). Next, imaging is performed by outputting control data for generating X-rays to the X-ray control unit 21 and outputting control data for detecting the intensity of transmitted X-rays to the image processing unit 24 ( S325).
Then, the X-ray generator 11 is supplied with a tube current of a predetermined current amount corresponding to the reference gradation data, generates an X-ray of a predetermined intensity, and supplies the X-ray of a sensitivity correction sample (standard sample) on the X-ray irradiation path. Irradiate. The transmitted X-ray that has passed through the sensitivity correction sample reaches the X-ray flat panel sensor 13, and its intensity is detected as a voltage signal for each of the many detection elements 13c. The detected voltage signal is converted into a luminance value corresponding to each detection element 13c by the digital conversion unit 13d.
[0060]
When the imaging is performed, the luminance value f (x, y, n), which is the gradation data for correction for each detection element 13c, is acquired from the X-ray flat panel sensor 13, and referring to the tube current correspondence table T2, FIG. 12 is stored in the sensitivity correction table T3 shown in the lower part (S330). This X-ray inspection apparatus performs sensitivity correction in which the luminance value f (x, y, n) is used as gradation data before correction, and the reference luminance value is used as gradation data after correction. Create table T3.
When a luminance value obtained by flowing a tube current having a current amount corresponding to the counter n to the X-ray tube 11a and storing it in the sensitivity correction table, it is determined whether or not imaging has been performed for tube currents having a current amount in all stages ( S335). If there is a current amount at a stage where imaging has not been performed, the processes of S310 to S335 are repeatedly performed, and if imaging has been performed for all current amounts, this flow ends.
[0061]
In this manner, the X-rays generated by sequentially supplying a plurality of stages of tube currents having different current amounts corresponding to the reference gradation data to the X-ray irradiating means are irradiated on the detecting elements, and are applied to a large number of detecting elements. X-ray intensity can be detected, and correction gradation data corresponding to the detected X-ray intensity can be obtained for each of the same number of detection elements.
The process of correcting the luminance value for each detection element using the created sensitivity correction table T3 can be performed according to the flowchart of FIG.
The X-ray inspection apparatus that performs the sensitivity correction table creation processing and the sensitivity correction processing according to the present embodiment constitutes the correction unit and the element-specific correction unit according to the present invention.
[0062]
As described above, the second embodiment has the same advantages as the first embodiment. That is, the thickness, size, and the like of the target sample can be precisely measured with a simple configuration, and the quality of the target sample can be more accurately determined. Since the gradation data is also corrected for each of a plurality of levels of reference gradation data, even if the sensitivity characteristics of the gradation data before correction differ for each detection element, the gradation is appropriately adjusted according to the size of the gradation data. Variations in data can be eliminated, and the target sample can be measured with higher accuracy than simply correcting the gradation data for each detection element. Since the offset existing in the gradation data before correction is deleted after the correction, the target sample can be measured with higher accuracy.
[0063]
In addition, even if the processing of correcting 5.76 million pixel gradation data for each detection element (pixel) in the embodiment is performed, the processing time is only about 5 seconds, but the data amount of the sensitivity correction table is increased and the table is referred to. If the correction process is performed only by using the correction process, the processing time can be further reduced. For example, in the above-described embodiment, three types of luminance values corresponding to the reference luminance values are stored for each pixel in the sensitivity correction table. However, even if ten types of luminance values are stored for each pixel, each reference luminance value may be stored. Is represented by a 32-bit floating point, which is 230 megabytes, and it is easy to secure such a storage capacity. Then, when processing for correcting gradation data of 5.76 million pixels is performed with reference to a sensitivity correction table storing ten types of luminance values for each pixel, the processing time is about 2 seconds.
Further, the gradation data corresponding to the pixel may be corrected collectively by the change characteristic or the like without correcting the gradation data for each detection element (pixel). Even in this case, since the gradation data is also corrected for each of a plurality of levels of reference gradation data, it is possible to correct the sensitivity characteristics of the gradation data before correction and measure the target sample more accurately. Become.
[0064]
(6) Summary:
The X-ray inspection apparatus of the present invention can be variously changed without changing its gist, and is not limited to the above-described embodiment.
For example, instead of creating a sensitivity correction table, an equation for calculating a corrected brightness value for each detection element may be created to correct the brightness value. The same effect can be obtained, and the target sample can be measured with higher accuracy.
In addition, a large number of detection elements may be arranged in a dot matrix shape arranged in a honeycomb shape or the like in addition to a dot matrix shape arranged in a vertical and horizontal order.
As described above, according to the present invention, according to various aspects, it is possible to provide an X-ray inspection apparatus and a control program for the X-ray inspection apparatus that can measure a target sample with higher accuracy. Further, the present invention is applicable as an X-ray inspection method.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of an X-ray inspection apparatus according to a first embodiment.
FIG. 2 is a diagram showing a schematic configuration of an X-ray tube.
FIG. 3 is a diagram illustrating an X-ray photon energy distribution of X-rays.
FIG. 4 is a block diagram schematically showing a configuration of an X-ray flat panel sensor.
FIG. 5 is a block diagram schematically showing a configuration of a sample moving mechanism.
FIG. 6 is a block diagram showing a schematic configuration of an X-ray control unit together with an X-ray tube.
FIG. 7 is a flowchart illustrating a sensitivity correction table creation process.
FIG. 8 is a diagram schematically illustrating the significance of a sensitivity correction table.
FIG. 9 is a diagram schematically showing a structure of a sensitivity correction table.
FIG. 10 is a flowchart illustrating a sensitivity correction process.
FIG. 11 is a flowchart illustrating a sensitivity correction table creation process according to the second embodiment.
FIG. 12 is a diagram schematically showing the structures of a tube current correspondence table and a sensitivity correction table.
[Explanation of symbols]
10 X-ray imaging mechanism
11 X-ray generator
11a ... X-ray tube
11b… Anode
11c ... Cathode
11d ... Electronic lens
11e ... Target
13 ... X-ray flat panel sensor
13a ... Scintillator
13b ... Light detection array
13c ... Detection element
13d Digital conversion unit
15 XY stage
17 ... Sensitivity correction sample stage
18. Sensitivity corrected sample (standard sample)
19 ... Blank
20 X-ray imaging control unit
21 X-ray control unit
21a ... Tube voltage control circuit
21b: tube current control circuit
22: Correction sample controller
23: Stage control unit
24 ... Image processing unit
25 ... CPU
26a ... output unit
26b ... input section
27… Memory
27a ... Control program
30 ... solder bump
31 ... Substrate
32 ... Tip
C1: X-ray irradiation path
T1, T3: sensitivity correction table
T2: Tube current table

Claims (11)

The target sample is irradiated with X-rays of a predetermined intensity, and the intensity of the transmitted X-ray transmitted through the target sample is detected for each of the detection elements by a large number of detection elements provided in a dot matrix form. An X-ray inspection apparatus for measuring gradation data corresponding to the intensity for each of the plurality of detection elements,
A standard sample having a predetermined X-ray transmission amount is irradiated with the X-rays, the intensity of the transmitted X-rays transmitted through the same standard sample is detected by the above-described many detection elements, and the intensity of the transmitted X-ray is detected. The correction gradation data to be obtained is obtained for each of the same number of detection elements, and based on the correction gradation data, the intensity of the transmitted X-ray transmitted through the target sample irradiated with the X-ray of the predetermined intensity is corresponded. An X-ray inspection apparatus, comprising: an element-by-element correcting unit that corrects the gradation data obtained by the above-described plurality of detection elements. The element-by-element correction means sequentially irradiates the X-rays to a plurality of standard samples having different X-ray transmission amounts corresponding to a plurality of levels of reference gradation data within a range that the gradation data can take, A large number of detection elements detect the intensity of transmitted X-rays transmitted through each standard sample, acquire correction gradation data corresponding to the detected transmitted X-ray intensity for each of the plurality of standard samples, and perform the correction. Based on the gradation data and the reference gradation data, the gradation data obtained corresponding to the intensity of the transmitted X-ray transmitted through the target sample irradiated with the X-rays of the predetermined intensity is referred to as the multi-step reference. The X-ray inspection apparatus according to claim 1, wherein correction is performed for each gradation data. The element-by-element correction means includes a sample moving mechanism capable of moving any of the plurality of standard samples to the X-ray irradiation path, and sequentially moving the plurality of standard samples to the X-ray irradiation path. 3. The X-ray inspection apparatus according to claim 2, wherein the correction gradation data is obtained while obtaining the correction gradation data. X-ray irradiating means capable of irradiating the target sample with X-rays and a stage capable of mounting the same target sample are provided, and the plurality of detection elements are connected to the X-rays of the X-ray irradiating means via the stage. The X-ray inspection according to any one of claims 1 to 3, wherein the X-ray inspection is arranged at a position facing the irradiation direction, and the standard sample is arranged between the X-ray irradiation unit and a stage. apparatus. The target sample is irradiated with X-rays of a predetermined intensity, and the intensity of the transmitted X-ray transmitted through the target sample is detected for each of the detection elements by a large number of detection elements provided in a dot matrix form. An X-ray inspection apparatus for measuring gradation data corresponding to the intensity for each of the plurality of detection elements,
X-rays generated by sequentially supplying a plurality of stages of tube currents having different current amounts to X-ray irradiating means for generating X-rays having an intensity corresponding to the current amount of the flowing tube current are irradiated on the detecting element, The detection element detects the intensity of the X-ray, obtains correction gradation data corresponding to the detected X-ray intensity for each of the plurality of detection elements, and, based on the correction gradation data, determines the predetermined intensity. X-rays comprising an element-by-element correcting means for correcting tone data obtained corresponding to the intensity of transmitted X-rays transmitted through a target sample irradiated with the X-rays for each of the plurality of detection elements. Inspection equipment. The element-specific correction means includes X-ray irradiating means capable of generating X-rays having an intensity corresponding to the current amount of the flowing tube current and irradiating the target sample with the X-rays. X-rays generated by sequentially supplying a plurality of stages of tube currents having different current amounts corresponding to the reference gradation data to the same X-ray irradiating means are radiated to the above-mentioned many detecting elements, The correction gradation data corresponding to the detected X-ray intensity is acquired, and the target sample irradiated with the X-rays of the predetermined intensity is transmitted based on the correction gradation data and the reference gradation data. The X-ray inspection apparatus according to claim 5, wherein the gradation data acquired corresponding to the intensity of the transmitted X-ray is corrected for each of the plurality of levels of reference gradation data. The element-by-element correction means creates a correction table in which the correction gradation data is used as the pre-correction gradation data and the reference gradation data is used as the post-correction gradation data to correspond to the gradation data before and after the correction. Then, the gradation data before correction corresponding to the intensity of the transmitted X-ray transmitted through the target sample irradiated with the X-ray of the predetermined intensity is acquired, and the gradation data before the correction is obtained by referring to the correction table. The X-ray inspection apparatus according to any one of claims 2 to 4, wherein the corrected gradation data is obtained. The target sample is irradiated with X-rays of a predetermined intensity, and the intensity of the transmitted X-ray transmitted through the target sample is detected for each of the detection elements by a large number of detection elements provided in a dot matrix form. An X-ray inspection method for measuring gradation data corresponding to intensity for each of the same number of detection elements,
A standard sample having a predetermined X-ray transmission amount is irradiated with the X-rays, the intensity of the transmitted X-rays transmitted through the same standard sample is detected by the above-described many detection elements, and the intensity of the transmitted X-ray is detected. The correction gradation data to be obtained is obtained for each of the same number of detection elements, and based on the correction gradation data, the intensity of the transmitted X-ray transmitted through the target sample irradiated with the X-ray of the predetermined intensity is corresponded. An X-ray inspection method, wherein the gradation data obtained by the correction is corrected for each of the plurality of detection elements. A predetermined amount of tube current is applied to X-ray irradiating means for generating X-rays having an intensity corresponding to the amount of flowing tube current, thereby generating X-rays and irradiating the target sample. X-ray inspection method for detecting the intensity of transmitted X-rays transmitted through the target sample by the detection elements for each of the detection elements, and measuring gradation data corresponding to the detected intensity of the transmitted X-rays for the same number of detection elements And
X-rays generated by sequentially supplying a plurality of stages of tube currents having different current amounts to the X-ray irradiating means are applied to the plurality of detection elements, and the X-ray intensity is detected by the detection elements. The correction gradation data corresponding to the intensity of the X-ray obtained is obtained, and based on the correction gradation data, the transmission X-ray transmitted through the target sample irradiated with the X-ray having the intensity with respect to the predetermined current amount is obtained. An X-ray inspection method, wherein the gradation data acquired corresponding to the intensity is corrected for each of the plurality of detection elements. The target sample is irradiated with X-rays of a predetermined intensity, and the intensity of the transmitted X-ray transmitted through the target sample is detected for each of the detection elements by a large number of detection elements provided in a dot matrix form. A control program for an X-ray inspection apparatus for measuring gradation data corresponding to intensity for each of the same number of detection elements,
A standard sample having a predetermined X-ray transmission amount is irradiated with the X-rays, and correction gradation data corresponding to the intensity of the transmitted X-rays transmitted through the standard sample detected by the large number of detection elements is transmitted. Along with acquiring for each of a large number of detection elements, based on the correction gradation data, the gradation data acquired corresponding to the intensity of the transmitted X-ray transmitted through the target sample irradiated with the X-ray of the predetermined intensity is obtained. A control program for an X-ray inspection apparatus, wherein a computer realizes the function of correcting for each of a large number of detection elements. A predetermined amount of tube current is applied to X-ray irradiating means for generating X-rays having an intensity corresponding to the amount of flowing tube current, thereby generating X-rays and irradiating the target sample. X-ray inspection apparatus that detects the intensity of transmitted X-rays transmitted through the target sample by the detection elements, and measures tone data corresponding to the detected transmitted X-ray intensity for the same number of detection elements. Control program,
X-rays generated by sequentially supplying a plurality of tube currents having different current amounts to the X-ray irradiating means are applied to the above-mentioned many detecting elements, and correspond to the intensity of the X-rays detected by the detecting elements. The correction gradation data to be obtained is obtained, and based on the correction gradation data, the X-rays having the intensity with respect to the predetermined current amount are obtained corresponding to the intensity of the transmitted X-ray transmitted through the irradiated target sample. A control program for an X-ray inspection apparatus, wherein the control program causes a computer to realize a function of correcting the gradation data for each of the plurality of detection elements.

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