Ki jan yo presize yon plak chofaj ak yon total espesifik ki endike (TIR) ​​pou aplikasyon presizyon?

Yon plak chofaj pou lyezon optik oswa pwosesis semiconductor wafer pa dwe sèlman "plat", men plat nan kèk mikron. Lang spesifikasyon pou sa a se Total Indicated Runout . Jwenn li kòrèkteman sou desen an detèmine tout pwosesis fabrikasyon an. Flatness mal defini ka bay kontak inegal, zòn cho, ak pati rejte. Yon TIR byen espesifye bay menm transfè tèmik soti nan plak la chofaj nan tout zòn nan k ap travay - yon absoli dwe kote presizyon se non an nan jwèt la. TIR oswa Total Indicated Runout sou yon plak chofaj? Total Indicated Runout se maksimòm fluctuation nan wotè yon sifas jan yo detèmine pa yon endikatè kadran pandan y ap vire pati a oswa analize sou yon zòn defini. Pou yon plak chofaj plat TIR se reyèlman yon mezi plat ak paralelis ansanm. Se endikatè a mete a zewo kont yon pwen referans ak Lè sa a, deplase sou figi a k ​​ap travay nan plak la. Nenpòt chanjman - pik oswa depresyon - yo note. Valè TIR a se diferans ki genyen ant lekti ki pi wo ak pi ba a atravè seri mezi ki endike a. Kritè TIR <0.025 mm (25 mikromèt) atravè yon plak dyamèt 300 mm vle di ke pa gen okenn pwen sou sifas la ki pi plis pase ± 0.0125 mm nan avyon referans lan. Nan aplikasyon ultra-presizyon, valè TIR de 0.010\\;mm oswa menm 0.005\\;mm ka mande. TIR obligatwa a souvan detèmine pa tolerans nan epesè nan objè a ke yo te trete oswa kontwòl la diferans ki nesesè pou yon pwosesis laminasyon oswa lyezon. Pi mens, pati ki pi sansib (egzanp, wafers semi-conducteurs, vè optik) mande pou pi etwat TIR. Poukisa li difisil pou jwenn yon TIR sere pou plak chofaj Yon plak chofaj se pa sèlman yon plak metal. Li swa bay jete-nan oswa sere-nan genyen siyon pou eleman chofaj oswa fouye pou aparèy chofaj katouch. Li ka gen pwi tèrmokapteur, twou aliye ak chanèl refwadisman. Tansyon entèn yo koze pa pwosesis pwodiksyon - D', soude, chalè tretman. Tansyon sa yo lage lè plak la chofe nan tanperati a k ​​ap travay kreye warpage. Yon plak ki plat nan tanperati nòmal ka bese pa 0.1 mm oswa plis nan 150 C. Nan pratik, flatness se yon karakteristik depandan tanperati nan yon plak chofaj. Kidonk TIR pou kont li pa sifi pou presize. Tanperati a nan ki mezi a fèt yo dwe espesifye. Yo ta dwe espesifye yon plak chofaj presizyon ak yon TIR mezire swa nan tanperati anbyen (avèk yon drift li te ye, akseptab nan tanperati opere), oswa pi bon, mezire nan tanperati a opere antisipe. Etap Pwosesis Pou Jwenn Yon TIR Precision Pou reyalize yon estanda TIR ki mwens pase 0.025 mm, yo mande yon seri aktivite fabrikasyon byen reflechi. Tansyon rès nan jan-resevwa ba oswa plak stock yo komen, akòz woule oswa ekstrizyon. Tansyon sa yo ka soulaje pa yon tranpe (di 2-4 èdtan nan 340C pou aliminyòm, oswa 600C pou asye) ak yon refwadisman ralanti. San yo pa pwosesis sa a, machin ki vin apre a pral dezekilib jaden an estrès ak plak la ta defòme lè aparèy chofaj la enèji . 2. Machin ki graj ak entegre nan aparèy chofaj Plak la se brut machin nan tou pre dimansyon nèt. Eleman chofaj yo pozisyone (pa egzanp, jete nan yon mwazi sab pou jete-nan aparèy chofaj oswa peze nan siyon machin). Etap sa a pote nouvo presyon akòz diferans nan ekspansyon tèmik ant djenn aparèy chofaj la ak materyèl la plak. Pou aplikasyon TIR egzak, aparèy chofaj la souvan jete nan yon nwayo aliminyòm separe epi ankò estrès -soulaje anvan sifas final. 3. Post-Asanble Tèmik Estrès-Solaj Yon fwa eleman chofaj yo konplètman implanté oswa kranpon, tout asanble plak la bay yon lòt soulaje estrès sik la. Sa a enpòtan. Nan sik sa a eleman yo tèt yo ap chofe nan yon tanperati ki pi wo pase tanperati sèvis espesifye a ak chalè a yo jenere atifisyèlman laj asanble a ak detann tansyon diferans. Sa a pafwa yo rele "siklèt tèmik" oswa "pre-estabilizasyon". 4. Manje ak presizyon Sifas k ap travay la se moulen ak yon moulen sifas gwo-fòma oswa moulen doub-disk. Manje retire sèlman dènye 0.2 a 0.5 mm nan materyèl epi li pwodui yon fini sifas (Ra) nan 0.8 µm oswa pi plis ak yon plat ki apwoche kapasite nan machin nan. Anba anviwònman reglemante, yon moulen sifas kontanporen ka pwodui yon TIR<0.010 mm for plates up to 600 mm in diameter. 5. Optional Final Lapping Lapping is essential for TIR specs tighter than 0.010 mm (i.e., <0.005 mm over 200 mm). Lapping employs a fine abrasive slurry between the plate and a precise flat lapping plate. It is a long procedure but near-optical flatness can be obtained. Semiconductor hot chucks or optical bond platen are often required to have lapped surfaces. Engineering Drawing – TIR Specification To effectively acquire a heating plate that meets the accuracy requirements, the TIR specification must be unambiguous and thorough. A typical callout on a drawing might be: The Total Indicated Runout (TIR) of the working surface shall not be greater than 0.020 mm as measured to ASME Y14.5M-1994. The measurement shall be made with the plate stabilised at 100 °C ± 5 °C over the whole working surface as described by diameter D. "No local deviation greater than 0.010 mm over any 25 mm square area is permitted." Key elements: The TIR limit. The measurement standard (ASME Y14.5 or ISO 1101).. . • Measurement temperature (room temperature, operating temperature or both). The TIR zone applicable (for example, "over the whole working surface" or "in the central 80% of the plate"). Any other "local flatness" requirement (e.g., waviness control) Never give a TIR without the temperature. A flat plate at room temperature may no longer be flat at 150 °C. For sensitive applications the manufacturer should be compelled to submit a flatness map at both ambient and operating temperature. Matching TIR to Application The TIR required must be defined by the thickness tolerance and compliance of the part being machined. Thick, inflexible parts (e.g. metal sheets >3 mm) - Yon TIR 0.05-0.10 mm plis pase 500 mm ka akseptab paske atik la pral konfòme oswa keratin tèmik pral ranpli twou vid ki genyen. Fim mens, fleksib oswa wafers (<0.5mm) - TIR must be <0.025mm. • Common TIR for semiconductor wafers produced on a vacuum chuck is <.010 mm. Optical contacts (no adhesive) – <0.005 mm TIR (lapping necessary). Laminating with rigid substrates - TIR <0.020 mm over the laminate area to avoid voids. Verification Procedures TIR needs to be verified by the buyer or end user upon receipt. A easy way is to utilise a dial test indicator on a surface plate. The heating plate is supported by three supports of precise height adjustment calibrated to a reference plane. The indicator is walked in a grid-like manner. For larger plates (>500 mm) yon machin mezi kowòdone (CMM) oswa yon entèferomètr lazè ofri done pi egzak. Si plak la espesifye ak TIR mezire nan tanperati opere, yo dwe fè yon tès chofaj kontwole. Plak la tension nan setpoint sèvis la epi yo pèmèt yo estabilize (anjeneral 30-60 minit) epi yo anrejistre TIR a ak yon endikasyon ki reziste chalè-oswa yon Capteur deplasman lazè ki pa-kontak. Yon koreksyon pou ekspansyon tèmik kanpe endikatè a obligatwa. Erè komen nan spesifikasyon TIR sou-ki espesifye - Espesifye TIR<0.005mm when the application only needs 0.05mm increases expense unnecessarily (lapping is expensive). Forgetting temperature - A TIR without a defined measuring temperature is unclear. A manufacturer may deliver a room temperature flat plate that bows in service to an unacceptable degree. Mounting Holes Ignored - The TIR standard should indicate if the measurement includes the area right above the fastener holes or if such areas are omitted. Overtightening of bolts leads to local distortion of the surface. There should be specific torque values for mounting shown on the drawing. No local flatness control - A plate can meet a global TIR of 0.025 mm and still have a sharp 0.020 mm hump over a 10 mm circle - a "waviness" concern. This is offset by further calls for "flatness over any 25 mm square". Cost Impact on TIR of Tightening The TIR specification and the manufacturing cost are not linearly related. A stress relieved plate stock can be milled by standard methods to a TIR <0.05 mm plate requiring little grinding. If the TIR is less than 0.025 mm, special cycles of grinding and stress alleviation are necessary. At TIR <0.010 mm, lapping and numerous cycles of thermal stabilisation are necessary, increasing or triple the cost. Thus, the engineer designing the plate should pick the least permissible TIR based on process physics, then add a little safety margin, but not specify a needlessly tight tolerance. Material Selection Aluminium (6061 or 7075) is the most frequent heating plate material because of its excellent thermal conductivity and ease of machining. Aluminium, however, has a rather high coefficient of thermal expansion (23 µm/m·K) and poor rigidity. Large aluminium plates (e.g. 600 mm diameter) will sag under their own weight unless they are adequately supported. For very tight TIR requirements, steel (16 µm/m.K) or aluminum-silicon carbide composites can be employed although they are heavier or more expensive. Summary : The Drawing as Contract for Performance Properly specifying the total suggested runout of the heating plate assures that the platen will really accomplish its job of providing uniform contact and heat, and that the manufacturing process is capable of meeting that spec. A drawing is a performance contract and the precise standards must be explicitly defined. The engineer gives the manufacturer a clear goal by defining the TIR limit, the measurement temperature, the area where the application is to be used and any local flatness requirements. The outcome is a heated plate that is predictable in the precision application -- be it glueing optical lenses, manufacturing semiconductor wafers or laminating flexible circuits. Flatness is not a luxury in such job. It is a process enabler.