Small join technology

Act chip way (Flip-chip) and carry bring automatic bond technology (TAB) as large-scale the development with VLSI, the number of lead of microelectronics parts of an apparatus also increases subsequently. Filar ball solder regards a kind of spot welding as the technology, it is to solder no matter quality, still solder the requirement that efficiency cannot get used to mass production, group solder technology emerge as the times require. Install chip law to be developed by IBM company in 60 time, basically use at thick film circuit. This kind of method is in prefab drill rod to expect protruding is nodded in the electrode on silicon chip, cream drill rod makings at the same time presswork to go up to the down-lead electrode of substrate a side, next silicon chip convert, make the drill rod on silicon chip expects protruding is nodded to it contrapuntal, classics after heating, make bilateral needle expects frit is an organic whole, realize join thereby. This kind of method applies to the requirement of miniaturization of microelectronics parts of an apparatus, tall function, but dot of protruding of drill rod makings is made complex, the visual examination after solder is painful, and need solder pre-treatment and standard of solder of strict control drill rod, application is so finite. Carry the belt is automatic be good at combining a technology is to be in those who be similar to 135 film is flexible carry take felt lame, body of down-lead block diagram is made via corroding on lame, the protruding dot that goes up with chip after that has link. In current TAB, what use extensively is to eletroplate the Au protruding dot on the Cu down-lead casing of Au and chip, undertake hot pressing solders. Its advantage is production efficiency is tall, defect is craft very complex also, cost is higher, and the versatility of chip is poor. 2. The method of solder of soft drill rod in small join technology is in small join technology, solder of soft drill rod basically uses the connection of terminal of Yu Wei electronic parts. Terminal join is to point to terminals of signal of microelectronics parts of an apparatus (terminal) with printed circuit board (PCB) go up corresponding solder dish the join between. From 1962 Japan rolls out array of bar of ball of substrate of pottery and porcelain (CBGA) , american RCA company rolled out a type resistor, capacitance 1966, phlips company put forward the surface formally to assemble 1971 (SMT) concept, to 1991 Motorola company rolls out array of bar of colophony substrate ball (PBGA) , make BGA technology trend economic change, join technology finished the terminal of microelectronics parts of an apparatus to insert outfit technology by via (THT) the historic flight to SMT, promoted the development of microelectronics technology greatly. 1. At present middling of microelectronics industry production sees technology of weak shot solder ministry PCB is stuck to insert mix outfit means, craft of commonly used solder of soft drill rod is mixed for wave crest solder shed solder again. (1) solder of wave crest of wave crest solder is pump of makings of drill rod of have the aid of expects melt state drill steel to ceaseless and perpendicular uphill flushs toward long and narrow exit, form the wave crest with 20 ～ tall 40mm. Can make drill rod expects so go up at PCB with fixed rate and pressure action, sufficient infiltration arrives wait for down-lead of soldering parts of an apparatus and circuit board between, made complete embellish is wet hand-in-hand travel solders. As a result of wave crest of drill rod makings flexible, although PCB is insufficient level off, should become warped only curvature is under 3 ％ , still attainable solder goodly quality. In THT craft, advocate via using Chan Bofeng solder. Right now its defect is drill rod expects wave crest is perpendicular up force, can bring concussion to a few lighter parts of an apparatus, cause float or empty solder. And in SMT craft, because the surface assembles element (SMD inserts outfit component without via (THD) in that way installation inserts aperture, the gas that the brandish after brazing flux be heated gives out nowhere dissipation, additionally SMD has certain height and breadth, and assemble density bigger (general 5 ～ 8 / Cm2) , the exterior tension action that drill rod expects will form screen effect, make drill rod expects very difficult timely profit is wet permeate every down-lead, use solder of odd wave crest to be able to produce many leakage solder or bridge to connect right now, develop solder of double wave crest again for this (see a picture 1) . Solder of double wave crest has around two wave crest, before one wave crest is narrower, wave height and wave are broad than be more than 1, peak end has the small wave crest that 3 crisscross arrange 2 ～ , in such bull, below the onflow wave function that controls ceaseless and rapid flow up and down, brazing flux gas is eliminated, exterior tension action also by abate, obtain thereby solder goodly quality. One wave crest is two-way wide Ping Bo after, drill rod expects even and flow is slow, can purify is redundant drill rod makings, eliminate burr, bridge to wait for weld defects repeatedly. Solder of double wave crest already was inserted in PCB stick mix mount to apply extensively. Its defect is PCB passes wave crest twice, be heated amount is larger, the warp of PCB changeful form with a few poorer hear resistance. To overcome the weakness of solder of double wave crest, develop a jet again in recent years hollow wave crest. It uses tailor-made electromagnetism pump to regard drill rod as pump of makings jet power, the magnetic field outside using and the double re-act that electric current flows in makings of melt drill rod are used, force drill rod to expect the direction that determines by left hand formula flows, and wave of eject clean heart. According to is hydromechanical principle, can make drill rod expects sufficient profit is wet PCB component, implementation is firm solder. Hollow wave and PCB contact length only 10 ～ 20mm, engage time only 1 ～ 2s, can reduce thermal shock consequently. (2) the join material that spreads solder to shed solder to use again again is drill rod makings creams, note through presswork or dripping wait for a method to cream drill rod makings Tu Fu is in PCB solder dish on, reoccupy is special equipment (stick a machine) above place SMD, heat next make drill rod makings fused, flow again namely, realize join thereby. All sorts of distinction that shed solder method again depend on heat source and heat the method is different. 1) infra-red shed solder again. Infrared radiate heats the law uses channel heating furnace commonly, heat source is given priority to with infrared radiate, apply to automation line big batch to produce. And facility cost is inferior, it is Japan is the at present most general shed solder method again. Because the difference of the depth of exterior color, material reachs the far and near that is apart from with heat source,its defect is SMD, absorbs quantity of heat also differs somewhat; The SMD with large volume can cause a shadow to small-sized SMD, made be heated is not worth and reduce solder quality; The set of temperature hard give attention to two or morethings is considerate. 2) steam photograph sheds solder again. Heat source comes from fluorine chloric alkyl is solvent (typical brand is FC-70) latent heat of saturated steam vaporization. PCB is placed in be full of saturated steam atmosphere, the condensation when vapour and SMD are contacted gives off vaporization latent heat to make drill rod makings creams melt flows again. Steam photograph sheds solder application again the widest is the United States. Its advantage is solvent vapour can arrive at each corner, heat is conducted even, achievable the high quality that has nothing to do with product geometry appearance solders; Solder temperature is accurate, (215 person 3) ℃ , won't produce overheat phenomenon. Defect is solvent price costly, manufacturing cost is high; If the operation is undeserved, solvent can produce poisonous fluorine to change hydrogenous He Yiding via adding pyrolysis Xi gas. 3) laser sheds solder again. Heat source comes from CO2 or YAG stimulates beam of light, be based on laser to come admirable directional with high power density, its characteristic is to heat process height is local change; Do not produce effect power, the parts of an apparatus with hot strong sensitivity won't get thermal shock; Weld time is short, solder nods microstructure to get refining, heatproof and fatigue function gets rising. Defect is to regard as shed the spot welding technology with solder only method again, manufacturing efficiency root is low. At present laser billows sheds solder to basically be used at down-lead pitch to be in 0.

65 ～ 0.

The high density under 5m is assembled. Develop like Philips company " Laser Number PLM1 " in wave crest solder or special IC is assembled after shedding solder again, down-lead pitch is amounted to 0.

2mm also won't the bridge is received. Laser sheds solder craft to be able to implement high automation again and offer a process to control. The laser with domestic successful development sheds solder equipment to use personal computer to undertake controlling to laser power source again, implementation increases the accurate output of hot energy, the location that solder chooses uses human rights to show teach way, solder the process is finished automatically below the control of personal computer. 2. Material of solder of soft drill rod is in small join technology, place is traditional solder Sn-Pb alloy and organic soft brazing flux more with material of solder of soft drill rod, general beard is cleaned after solder. In recent years, as international the society takes environmental protection seriously of the problem increasingly and intense market competes, afterwards develops foreign photograph to avoid clean brazing flux and material of the drill rod that do not have Pb, commercial already. (1) avoid clean brazing flux Freon (CFC) solvent is solder of soft drill rod the main solvent with residual brazing flux is cleaned in the process, already signed on international banned the convention that uses CFC in the round 2000. Use avoid clean brazing flux but purify cleans measure, reduce the manufacturing facilities of earning and space; Save the cost that waits for a respect with processing of the material that cleans working procedure to be linked together, the sources of energy, trash; With existing clean the microelectronics parts of an apparatus with antipathic dissolvent attainable wide application. Avoid typically clean brazing flux to include 2 ％ ～ 5 ％ (quality mark) solid composition, will reduce solid ingredient through increasing the quantity of solvent and the amount that reduce colophony and activator. Activator system is special the choice is opposite situation sex, reduce its with the oldest rate long-term caustic. Carrier is colophony or man-made colophony, modified colophony commonly, because contain brazing flux of resinous low broken bits to still contain halide, because this man-made colophony is considered as optimal choice. Because a large number of alcohol are contained in injection, because this must join other dissolvent or vesicant promote,send bubble, in order to make sure brazing flux can bring to bear on at printed circuit board go up. But, what the vesicant of excessive will father to affect brazing flux again is caustic. Avoid the technical difficulty that cleans brazing flux to be as follows: 1) brazing flux pH indicator is optimized, can generate sufficient profit wet, and utmost decreases residual; 2) the drill rod dosage to give working procedure certainly, need to make clear its density. But because its comprise medium alcohol to have very high vapour pressure, density is controlled hard; 3) provide water imbibition as a result of alcohol, avoid clean brazing flux water imbibition apparent. And the moisture of the excessive in brazing flux will restrain brazing flux active, cause metallization oxidation; 4) because contain a large number of alcohol, brazing flux of low broken bits is very difficult epispastic (the important method that brazing flux brings to bear on in wave crest solder) ; 5) the solder of soft drill rod that is the high quality that finish is assembled, avoid the craft parameter window that cleans brazing flux requirement more narrow. (2) the solder of tradition of makings of the drill rod that do not have Pb is Sn-Pb alloy, pb has noxiousness. The technical key that development expects without Pb drill rod depends on finding a kind or a few kinds of alloying element, the alloy that makes its and Sn are formed has similar melting point, need not change existing craft condition thereby and come true to be replaced immediately, at the same time its wetability can answer to comparative with Sn-Pb alloy. Abroad makings of each the drill rod that do not have Pb that main company rolls out him in succession is patent recipe, but in be being produced actually at present, have not apply in great quantities. CNC Milling CNC Machining