JPS6331343B2 - - Google Patents
Info
- Publication number
- JPS6331343B2 JPS6331343B2 JP58155176A JP15517683A JPS6331343B2 JP S6331343 B2 JPS6331343 B2 JP S6331343B2 JP 58155176 A JP58155176 A JP 58155176A JP 15517683 A JP15517683 A JP 15517683A JP S6331343 B2 JPS6331343 B2 JP S6331343B2
- Authority
- JP
- Japan
- Prior art keywords
- polishing
- polished
- crystallized glass
- less
- fine powder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000005498 polishing Methods 0.000 claims description 33
- 239000011521 glass Substances 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 15
- 239000000843 powder Substances 0.000 claims description 13
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 11
- 239000007788 liquid Substances 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 230000003746 surface roughness Effects 0.000 description 13
- 239000010409 thin film Substances 0.000 description 11
- 239000000758 substrate Substances 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 239000006061 abrasive grain Substances 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 230000002393 scratching effect Effects 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000002925 chemical effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000001788 irregular Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005685 electric field effect Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- 229910000889 permalloy Inorganic materials 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000004439 roughness measurement Methods 0.000 description 1
- 229910000702 sendust Inorganic materials 0.000 description 1
- 125000005372 silanol group Chemical group 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B37/00—Lapping machines or devices; Accessories
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
Description
【発明の詳細な説明】
この発明は、薄膜磁気ヘツド用の結晶化ガラス
基板表面を表面粗度50Å以下に精密研摩仕上する
研摩方法に関する。
現在、磁気ヘツドは、オーデイオ用テープレコ
ーダー、ビデオ用テープレコーダー、データーレ
コーダー、コンピユーター用デイスク，ドラム等
の磁気記録の書き込み読み取りに、広く用いられ
ているが、さらに、磁気テープのメタルテープ
化、蒸着テープ化、あるいは記録方式のPCM化、
コンピユータの高速化，高記録密度化が進められ
ている。
磁気ヘツドは、これらの高記録密度化に対応す
るため、従来の巻線法バルクヘツドからＩ・Ｃテ
クノロジーを用いて作製され、比較的容易にマル
チトラツク化、狭トラツク化が達成できる薄膜磁
気ヘツドへと変換されつつある。
この薄膜磁気ヘツド用基板の１つとして、フオ
トエツチングが容易で、熱膨張係数をセンダスト
やパーマロイ等の軟磁性薄膜のそれに容易に合致
させることができ、組織が実質的に結晶化されい
る結晶化ガラスが多用されている。また、薄膜磁
気ヘツド用基板はその表面に多種の薄膜パターン
を被着形成する必要から、基板表面はできるだけ
精密平面に仕上げなければならない。
再生用に用いる磁気抵抗型薄膜磁気ヘツドの場
合、基板上に形成する素子の薄膜パターン厚みは
数100Åであり、基板仕上表面に突起，凹部ある
いは結晶段差，小孔等の欠陥が点在して露出する
と、磁気ヘツドパターンの微細化やマルチトラツ
ク化に伴ない、製造工程あるいは磁気ヘツド特性
上に下記の多くの問題を生じるため、基板表面粗
度を50Å以下に精密研摩する必要がある。
例えば、基板表面上の該欠陥部において、コン
ダクターの断線の恐れがあり、磁気抵抗型の場
合、素子幅が数μｍ程度であるので再生出力の低
下を来たしたり、また、該欠陥部近傍には残留歪
が存在して不均一な応力場が形成されており、こ
の上に磁性薄膜を被着すると残留歪が転写する恐
れがある等、種々の問題があつた。
この薄膜磁気ヘツドは、Ｉ・Ｃテクノロジーに
より量産製造されるため、上述した表面欠陥のあ
る基板を使用すると、製造歩留の低下のみなら
ず、磁気ヘツドとしての信頼性低下、電磁変換特
性の低下を招来することになり、かかる基板表面
の精密研摩方法が特に重要になつてくる。
従来、結晶化ガラスの精密研摩方法として、フ
オトマスク，レンズ等に適用されていた溶融型非
晶質ガラス研摩法が採用されていた。この研摩方
法は、酸化セリウムやベンガラを砥粒とし、レン
ズ等の表面を50Å以下の粗度に仕上げることがで
きる。ところが、結晶化ガラスに適用しても、材
質が実質的に結晶化されているため、研摩面に微
細突起や凹部が生成し、250Å程度の表面粗度し
か得られない問題があつた。
この発明は、かかる現状に鑑み、従来研摩方法
で生成する微細突起や凹部を防止し、50Å以下の
表面粗度が得られる結晶化ガラスの精密研摩方法
を目的としている。
すなわち、この発明は、単位体積当りの表面積
が130m2／ｇ以下で、形状が実質的に形状の粒径
320Å以下の無水アルミナ微粉末を純水中に懸濁
させたPH４〜５の液を研摩液とし、該研摩液中で
被研摩結晶化ガラスとラツプ盤を対向させて、ラ
ツプ荷重0.1Kg／cm2〜５Kg／cm2を加えながら相対
回転させ研摩することを特徴とする結晶化ガラス
の精密研摩方法である。
研摩対象の結晶化ガラスは、材質が実質的に結
晶化されたガラスでいずれの成分のものでもよい
が、LiO2，SiO2，Ag，Ceを主成分とするものが
好ましい。
純水中に懸濁させる無水アルミナ微粉末は、粒
径が320Å以下であり、乾式製法により得られる
が、その単位体積当りの表面積が130m2／ｇを越
える場合、粒形状が不規則形状となり、ラツプ時
に研摩面に対する切削・引掻作用が強く、得られ
る表面粗度が劣化し、研摩面に微細突起，凹部が
発生し易くなるので、単位体積当りの表面積は
130m2／ｇ以下とする。
この発明に用いる無水アルミナ微粉末乾式製法
により得られるため、湿式製法による含水アルミ
ナに比べ、活性面積が100％と大きいため、反応
性に富み、加工効率を向上させるケミカル効果が
得られ、また、純度は99.9％以上となり微粉末に
よる表面への汚染が少なく研摩加工が安定する。
水溶液はPH４〜５でシラノール基を呈し、ケミカ
ル効果が得られる。また、粉末形状が実質的に球
状であるため、研摩表面に対する切削，引掻作用
が少なく、研摩表面品位向上に有効である。結晶
化ガラスの主成分であるSiO2は負に帯電してお
り、微粉末自体は正に帯電するため、SiO2と無
水アルミナ粉末の懸濁液は電界効果により、加工
作用砥粒数が増加することになり、加工能率の増
大と共に凝集効果により、加工単位は数10Åとな
り、結晶化ガラス表面を50Å以下に精密研摩する
ことができると考えられる。
また、無水アルミナ微粉末の粒径が320Åを越
えると、被研摩表面に疵を形成し、表面粗度を劣
化させるので好ましくない。
研摩条件として、ラツプ荷重は、0.1Kg／cm2未
満では所望の表面粗度が得られず、かつ加工能率
が低く、また、5.0Kg／cm2を越えると加工効率の
点では好ましいが、ラツプ装置の大規模化に伴な
うコスト高と、研摩精度が悪化するので好ましく
ない。
また、ラツプ盤としては、Sn，Pb，はんだ合
金等の軟質金属あるいはクロス等が最適である。
以下に、実施例を説明する。
被研摩結晶化ガラスには、フオトセラム（商品
名，コーニング社製造）を使用し、その試料は長
さ25mm×幅25mm×厚み１mm寸法で、被研摩面粗度
300Åであつた。
研摩液は、単位体積当り表面積90m2／ｇ〜120
m2／ｇ、粒径300Åの無水アルミナ微粉末を、純
水中に1wt％分散させたPH４の懸濁液を使用し
た。
ポリツシヤーには、350mmφのSn盤を用い、こ
のポリツシヤー表面にフオトセラムの被研削面を
当接させ、回転数60rpm、ラツプ荷重0.5Kg／cm2，
３Kg／cm2の荷重負荷の加工条件で、両者を相対的
に回転させ、研摩加工中、100c.c.／ｈの割合で研
摩液を連続滴下しながら、30分間研摩を実施し
た。
また、比較のため、砥粒にCeO2を使用した研
摩液の場合（比較例Ｃ）、含水アルミナ微粉末を
使用した研摩液の場合（比較例Ｄ）及び本発明と
同一の無水アルミナ微粉末を使用した研摩液を用
いて本発明条件外のラツプ荷重の場合（比較例
Ｅ）の各種加工条件で研摩した。この際の研摩条
件並びに被研摩材料の表面粗度を測定し、本発明
方法で得られた表面粗度測定結果と共に、第１表
に示す。
被研摩面の表面粒度は、表面段差測定器
（Talystep装置、スタイラス，0.5μｍ，針圧７mg）
を使用して測定し、表面部の突起及び凹部状態は
ノマルスキー微分干渉顕微鏡を使用して測定し
た。
第１表から明らかな如く、従来のガラス研摩方
法による比較例Ｃの場合は、結晶化ガラスに対し
ては300Åの表面粗度しか得られず、また、含水
アルミナ微粉末を使用した場合は、粒形状が不規
則で球状でなく、表面積が大きく、切削や引掻き
作用が大で表面粗度が劣化しており、さらに、本
発明方法の研摩液を使用しても、ラツプ荷重が条
件外であると、表面粗度は200Åしか得られず、
いずれの場合も、結晶化ガラスの精密研摩には不
適であるのに対し、本発明方法の場合は、結晶化
ガラス表面には突起や凹部の発生がなく、20Åの
すぐれた表面粗度が得られたことが分る。また、
偏光回折結果のパラメータΔが小さいことから
も、本発明方法による精密研摩は加工歪が著しく
小さいことが分る。
ちなみに、本発明Ａと比較例Ｃの各々の被研摩
面表面粗度を測定し、第１図，第２図の２種のス
ケールでグラフに表示する。第１図に示す本発明
による被研摩面は、第２図の従来方法による被研
摩面に対して著しく精密平坦面を得られることが
明白である。
すなわち、この発明による結晶化ガラスの精密
研摩方法により、薄膜磁気ヘツドの信頼性、電磁
変換特性及び歩留の向上に極めて有効なことが分
る。
【表】DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polishing method for precision polishing the surface of a crystallized glass substrate for a thin film magnetic head to a surface roughness of 50 Å or less. At present, magnetic heads are widely used for reading and writing magnetic recording in audio tape recorders, video tape recorders, data recorders, computer disks, drums, etc., but they are also used to convert magnetic tapes into metal tapes, vapor-deposited magnetic tapes, etc. Tape or PCM recording method,
Computers are becoming faster and recording density higher. In order to accommodate these higher recording densities, magnetic heads have changed from conventional wire-wound bulk heads to thin film magnetic heads, which are manufactured using IC technology and can relatively easily achieve multi-track and narrow tracks. It is being converted into As one of the substrates for this thin film magnetic head, it is easy to photoetch, the coefficient of thermal expansion can be easily matched to that of soft magnetic thin films such as sendust or permalloy, and the structure is substantially crystallized. Glass is often used. Further, since it is necessary to form various thin film patterns on the surface of a substrate for a thin film magnetic head, the surface of the substrate must be finished as precisely and flatly as possible. In the case of magnetoresistive thin film magnetic heads used for playback, the thin film pattern of the element formed on the substrate is several hundred angstroms thick, and the finished surface of the substrate is dotted with defects such as protrusions, recesses, crystal steps, and small holes. If exposed, many of the following problems will occur in the manufacturing process or in the characteristics of the magnetic head as magnetic head patterns become finer and more multitrack. Therefore, it is necessary to precisely polish the substrate surface to a roughness of 50 Å or less. For example, there is a risk of the conductor breaking at the defective part on the substrate surface, and in the case of a magnetoresistive type, the element width is about several micrometers, which may cause a drop in the reproduction output. The presence of residual strain forms a non-uniform stress field, and when a magnetic thin film is deposited thereon, there are various problems such as the possibility that the residual strain will be transferred. Since this thin film magnetic head is mass-produced using I/C technology, if a substrate with the above-mentioned surface defects is used, not only will the manufacturing yield decrease, but also the reliability of the magnetic head will decrease, and the electromagnetic conversion characteristics will decrease. Therefore, a precision polishing method for the substrate surface becomes particularly important. Conventionally, as a precision polishing method for crystallized glass, a fused amorphous glass polishing method, which is applied to photomasks, lenses, etc., has been adopted. This polishing method uses cerium oxide or red iron abrasive grains and can finish the surface of lenses, etc. to a roughness of 50 Å or less. However, even when applied to crystallized glass, since the material is substantially crystallized, fine protrusions and depressions are generated on the polished surface, resulting in a problem that only a surface roughness of about 250 Å can be obtained. In view of the current situation, the present invention aims to provide a precision polishing method for crystallized glass that prevents the formation of minute protrusions and recesses that are produced by conventional polishing methods and provides a surface roughness of 50 Å or less. In other words, the present invention provides particles with a surface area per unit volume of 130 m 2 /g or less and a substantially shaped particle size.
Anhydrous alumina fine powder of 320 Å or less is suspended in pure water and has a pH of 4 to 5 as a polishing liquid.The crystallized glass to be polished is placed in the polishing liquid and a lapping plate is placed facing the lapping plate to apply a lapping load of 0.1 kg/cm. This is a precision polishing method for crystallized glass, which is characterized by polishing by relative rotation while applying 2 to 5 kg/cm 2 . The crystallized glass to be polished may be substantially crystallized glass and may be made of any component, but it is preferably one whose main components are LiO 2 , SiO 2 , Ag, and Ce. The anhydrous alumina fine powder suspended in pure water has a particle size of 320 Å or less and is obtained by a dry manufacturing method, but if the surface area per unit volume exceeds 130 m 2 /g, the particle shape becomes irregular. During lapping, the cutting and scratching action on the polished surface is strong, the resulting surface roughness deteriorates, and fine protrusions and depressions are likely to occur on the polished surface, so the surface area per unit volume is
130m 2 /g or less. Since the anhydrous alumina used in this invention is obtained by the dry manufacturing method of fine powder, the active area is 100% larger than that of hydrated alumina produced by the wet manufacturing method, so it is highly reactive and has a chemical effect that improves processing efficiency. The purity is 99.9% or higher, which means less contamination of the surface by fine powder and stable polishing.
The aqueous solution exhibits silanol groups at pH 4 to 5, and a chemical effect can be obtained. Furthermore, since the powder shape is substantially spherical, there is little cutting or scratching action on the polished surface, which is effective in improving the quality of the polished surface. SiO 2 , the main component of crystallized glass, is negatively charged, and the fine powder itself is positively charged, so the number of abrasive grains for processing increases due to the electric field effect in a suspension of SiO 2 and anhydrous alumina powder. Therefore, due to the increase in processing efficiency and the agglomeration effect, the processing unit becomes several tens of angstroms, and it is thought that the surface of crystallized glass can be precisely polished to a depth of 50 angstroms or less. Furthermore, if the particle size of the anhydrous alumina fine powder exceeds 320 Å, it is not preferable because it will form scratches on the surface to be polished and deteriorate the surface roughness. As for the polishing conditions, if the lap load is less than 0.1 kg/cm 2 , the desired surface roughness cannot be obtained and the processing efficiency is low, and if it exceeds 5.0 kg/cm 2 , although it is preferable in terms of processing efficiency, the lap load is This is not preferable because it increases the cost as the scale of the device increases and the polishing accuracy deteriorates. In addition, soft metals such as Sn, Pb, solder alloys, cloth, etc. are most suitable for the lap board. Examples will be described below. Photoceram (trade name, manufactured by Corning Inc.) was used as the crystallized glass to be polished, and the sample had dimensions of 25 mm in length x 25 mm in width x 1 mm in thickness, and the roughness of the surface to be polished was determined.
It was 300Å. The polishing liquid has a surface area of 90 m 2 /g to 120 m 2 /g per unit volume.
A PH4 suspension in which 1 wt % of anhydrous alumina fine powder having a particle diameter of 300 Å and m 2 /g was dispersed in pure water was used. A 350 mmφ Sn disc was used as the polisher, and the polished surface of the photoceram was brought into contact with the polisher surface, at a rotation speed of 60 rpm and a lap load of 0.5 Kg/cm 2 .
Under processing conditions of a load of 3 Kg/cm 2 , both were rotated relative to each other, and polishing was performed for 30 minutes while continuously dropping the polishing liquid at a rate of 100 c.c./h. In addition, for comparison, a case of a polishing liquid using CeO 2 as the abrasive grains (Comparative Example C), a case of a polishing liquid using a hydrated alumina fine powder (Comparative Example D), and an anhydrous alumina fine powder same as the present invention are also shown. Polishing was carried out under various processing conditions using a polishing liquid using a polishing solution using a lap load other than the conditions of the present invention (Comparative Example E). The polishing conditions at this time and the surface roughness of the material to be polished were measured, and are shown in Table 1 together with the surface roughness measurement results obtained by the method of the present invention. The surface grain size of the surface to be polished was measured using a surface step measuring device (Talystep device, stylus, 0.5 μm, stylus force 7 mg).
The state of protrusions and recesses on the surface was measured using a Nomarski differential interference microscope. As is clear from Table 1, in the case of Comparative Example C using the conventional glass polishing method, a surface roughness of only 300 Å was obtained for crystallized glass, and when using hydrated alumina fine powder, The grain shape is irregular and not spherical, the surface area is large, the cutting and scratching action is large, and the surface roughness is deteriorated.Furthermore, even if the polishing liquid of the present invention is used, the lap load is outside the conditions. If there is, a surface roughness of only 200 Å can be obtained,
In either case, it is unsuitable for precision polishing of crystallized glass, whereas in the case of the method of the present invention, there are no protrusions or depressions on the surface of crystallized glass, and an excellent surface roughness of 20 Å is obtained. I can see that it was done. Also,
The fact that the parameter Δ of the polarization diffraction results is small also shows that precision polishing according to the method of the present invention causes extremely small processing distortion. Incidentally, the surface roughness of each polished surface of Invention A and Comparative Example C was measured and graphed on two scales shown in FIG. 1 and FIG. 2. It is clear that the surface to be polished according to the present invention shown in FIG. 1 provides a much more precisely flat surface than the surface to be polished according to the conventional method shown in FIG. That is, it can be seen that the precision polishing method for crystallized glass according to the present invention is extremely effective in improving the reliability, electromagnetic conversion characteristics, and yield of thin film magnetic heads. 【table】
第１図と第２図は、被研摩面の表面状態を縦軸
の深さ方向、横軸の水平方向で表わしたグラフ
で、第１図が本発明方法、第２図が比較例Ｃの場
合である。
Figures 1 and 2 are graphs showing the surface condition of the surface to be polished with the vertical axis in the depth direction and the horizontal axis in the horizontal direction. This is the case.
Claims (1)
形状が実質的に球状の粒径320Å以下の無水アル
ミナ微粉末を純水中に懸濁させたPH４〜５の液を
研摩液とし、該研摩液中で被研摩結晶化ガラスと
ラツプ盤を対向させて、ラツプ荷重0.1Kg／cm2〜
５Kg／cm2を加えながら相対回転させ研摩すること
を特徴とする結晶化ガラスの精密研摩方法。1 The surface area per unit volume is 130m 2 /g or less,
Anhydrous alumina fine powder with a particle size of 320 Å or less, which is substantially spherical in shape, is suspended in pure water and has a pH of 4 to 5 as a polishing liquid, and the crystallized glass to be polished and the lapping plate are placed opposite each other in the polishing liquid. Let the wrap load be 0.1Kg/cm 2 ~
A precision polishing method for crystallized glass characterized by polishing by relative rotation while applying 5 kg/cm 2 .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58155176A JPS6048252A (en) | 1983-08-24 | 1983-08-24 | Fine polishing of crystallized glass |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58155176A JPS6048252A (en) | 1983-08-24 | 1983-08-24 | Fine polishing of crystallized glass |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6048252A JPS6048252A (en) | 1985-03-15 |
| JPS6331343B2 true JPS6331343B2 (en) | 1988-06-23 |
Family
ID=15600152
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP58155176A Granted JPS6048252A (en) | 1983-08-24 | 1983-08-24 | Fine polishing of crystallized glass |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6048252A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4632774A (en) * | 1983-09-14 | 1986-12-30 | The Standard Oil Company | Process for reforming alcohols |
| JPS63114866A (en) * | 1986-10-31 | 1988-05-19 | Hoya Corp | Method of processing glass |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57132964A (en) * | 1981-02-06 | 1982-08-17 | Sumitomo Special Metals Co Ltd | Precision processing method of single crystal ferrite |
-
1983
- 1983-08-24 JP JP58155176A patent/JPS6048252A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57132964A (en) * | 1981-02-06 | 1982-08-17 | Sumitomo Special Metals Co Ltd | Precision processing method of single crystal ferrite |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6048252A (en) | 1985-03-15 |
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