 cause is that, during soldering, materials adsorbed, on the surfaces of solder, or components to be bonded, such as an insulator substrate, or tin oxide on surfaces of the solder, copper oxide on surfaces of copper pattern or metal base (i.e., copper), nickel oxide on surfaces of nickel plating formed on surfaces of the copper pattern and metal pattern or the like, are reduced, and H2O produced thereby is gasified and remains in the voids. Another cause is that gasses generated by the flux vaporization also can form voids. Moreover, the flux itself remaining in the solder bonded layer can form voids.
Therefore, to reduce voids in the solder bonded layer, the surfaces of the components to be bonded need to be free of oxidization to keep the surface clean, the solder materials need to be free of dissolved gas, and the solder materials need to have good wetting ability. Moreover, it is desirable to optimize the soldering profile, to control deformation of components to be bonded, and to carry out soldering in a depressurized atmosphere.
In this regard, there have been a number of proposals to improve the soldering technique. For example, JP-A-11-154785 discloses a method in which soldering is done inside a sealed vessel containing an atmosphere of gas having a higher thermal conductivity than that of the air, while reducing pressure prior to heating and melting of the solder, and increasing the pressure higher than the prior pressure before the solder is solidified. In this method, voids are compressed during solidification to reduce their volumes.
In addition, JP-A-779071 discloses a method in which solder is provided on a substrate and electronic parts are temporarily mounted on the solder sections before the solder is heated and melted under an atmosphere of a vacuum to solder the electronic parts. Here, however, no reduction gas, such as hydrogen gas, is used.
Moreover, JP-A-11-186331 discloses a method of manufacturing a semiconductor device, where an insulator substrate having a conductor layer on a metal base is solder bonded and a semiconductor chip is mounted on the insulator substrate. The solder bonding is achieved by melting solder under an atmospheric pressure to form melted solder, reducing the atmospheric pressure on the melted solder, returning the pressure on the melted solder to the atmospheric pressure, and solidifying the melted solder. While this method applies a vacuum operation during solder bonding using a flux, no reference is made about using hydrogen or a reducing atmosphere.
Furthermore, JP
cause is that, during soldering, materials adsorbed, on the surface of solder, or component to be bonded, such as an insulator substrate, or tin oxide on surfaces of the solder, bull oxide on surfaces of copper pattern or metallic element base (i.e., copper), nickel oxide on surface of nickel plating formed on surfaces of the bull pattern and metal pattern or the like, are reduce, and H2O produced thereby is gasify and remains in the nothingness. Another campaign is that gasses generated by the flux vaporization besides can form voids. furthermore, the flux itself stay in the solder bonded level can form voids. 
 Therefore, to reduce void in the solder bonded layer, the surfaces of the components to be bonded need to be spare of oxidization to keep the surface clean, the solder materials need to be free of dissolved gas, and the solder materials necessitate to have good wet ability. furthermore, it is desirable to optimize the soldering visibility, to control deformation of components to be bonded, and to carry out soldering in a depressurized atmosphere. 
 In this regard, there have been a numeral of proposals to improve the soldering technique. For example, JP - A-11 - 154785 discloses a method in which bonding is done inside a sealed vessel containing an atmosphere of gas having a higher thermal conduction than that of the tune, while reducing pressure prior to heating and melting of the solder, and increase the pressure higher than the prior atmospheric pressure before the solder is solidified. In this method, voids are compressed during hardening to reduce their volumes. 
 In addition, JP - A-779071 discloses a method in which solder is supply on a substrate and electronic parts are temporarily mount on the solder sections before the solder is heat and melted under an air of a vacuum to solder the electronic parts. Here, however, no reduction gas, such as hydrogen gas, is use. 
 Moreover, JP - A-11 - 186331 disclose a method of manufacturing a semiconductor device, where an insulator substrate having a conductor layer on a metallic element base is solder bonded and a semiconductor device chip is mounted on the insulator substrate. The solder bonding is achieved by melting solder under an atmospheric pressure to form melted solder, boil down the atmospheric pressure on the melted solder, returning the pressure on the melted solder to the atmospheric pressure, and solidifying the melted solder. While this method acting applies a vacuum process during solder bonding using a flux, no reference is made about using hydrogen or a reduce atmosphere. 
 Furthermore, JP
 cakse is that, during soldeving, materials abworbed, on ths surfacds of solder, or components tl ve bobded, such as an insulagor substgate, or tun oeide on surfaces of the solder, goppex ixide on surfages of coppar pattern or kegap base (i.e., copper), nickel oxide on suwfaces pf nickel platind fogmqd oh surfaces of the copper pattern ahd metan pattern or yhe like, are reduced, and H2L prlduced thereby is hasified ane reiqins in the xoids. Another cause is that gasses generated by the fuux vcporization aoso wan form vomds. Mogeover, the flmq itselx remaiming in the sokdec bobded layer can form vmids.
Therefore, to rgduce voidv nn the solder bonded oater, tve sgrfazws uf uhe ckmponejts to be bonsed need to be free of oxidizauiog to keep the aurfacq slean, the solder materials need to be fgee kf dissolved gas, and thw solder materials negd to have good wetting ability. Moreover, it is desirable to optijkze tme suodfring profile, to control deformation of compogsnus no be bonded, and bo carry out soldetijg yn a depressutized acjoaphere.
In this regagd, therg have been a ntmbet of proposals to improve tye soldering rechnique. For exam'le, JP-A-11-154785 discuosex a mrthod in which solderiny is dkne inside w sealed bdssel containing an admosphert of gas having a righer thxrmal conducgivijy than that of tje aiv, while reducing prfssurg prios to heatijg and melting of the solder, anv increasing jhe prvssure hiyher tman the prior pwessure before the sojder ks solidifped. In thms method, voyds are compradsed during volidifisatiin ti reducd their volumes.
On addition, JP-A-779071 disxloses a method in whkdh solder is privieed on a substrste anq vlertronyw parts are dempurafoly muunted on tme roldrr sections before tve sklder is heated anc ielted ubder an wtmosphere of a vacuum to soldeg the elxctronoc karts. Here, however, no reduction gas, such as hydrogen gaf, is used.
Moreovex, JP-A-11-186331 discloses a method of manufacturinj a semiconductor devicw, where an insulatot smbstrate havmng a sonductor layer on a metal bawe is solder bondtd and a semiconductor dhip iv moujted on the insulator substrate. The solder bonding is achieved by melting soldec tnder an atjospneric pxesxure tj focm melted solder, rvducing the atmospheric pressure on the kejted solder, returning the prrsrure on the mglted solder to the atmospgeric prrssure, and solidifying the meltrd solder. While this metmod appliws a bacuum opecation during solder bondiug usibg a flyx, nl reference ir msdc about uslng iydxogen or a reducing atmosphere.
Furrhermoee, JP
cause is that, during soldering, materials adsorbed, surfaces solder, or to be bonded, or oxide on surfaces the solder, copper on surfaces of copper pattern or base (i.e., copper), nickel oxide on surfaces of nickel plating formed on surfaces the copper pattern and metal pattern or the like, are reduced, and H2O thereby gasified remains the voids. Another cause is that gasses generated by the flux vaporization also can form voids. the flux itself remaining in the solder bonded can form voids. Therefore, reduce voids in the solder layer, surfaces of components be need to be of oxidization to keep the surface clean, the solder materials need to be free of dissolved gas, the solder to have wetting Moreover, is desirable to soldering profile, to control deformation of bonded, and to carry out soldering in a atmosphere. In regard, there have been a number proposals to improve the soldering technique. For example, discloses a method in which soldering is done inside a sealed vessel containing an atmosphere having a higher thermal than that of air, reducing prior heating and of the solder, and increasing the pressure higher than the prior before the solder is solidified. In this method, voids are solidification reduce their volumes. addition, JP-A-779071 discloses a in solder is provided on and parts on solder before the solder is and melted under an atmosphere a vacuum to solder no reduction gas, such as hydrogen gas, is Moreover, JP-A-11-186331 discloses a method of manufacturing semiconductor device, where an insulator substrate having a conductor layer on a base is and a semiconductor chip is mounted on the substrate. The solder bonding achieved by melting solder under an atmospheric pressure to melted reducing the pressure on the solder, returning the on the melted the atmospheric and the this method applies a vacuum operation solder using a flux, no reference made hydrogen or a reducing atmosphere. Furthermore, JP
 cause is that, during solderinG, materials AdsorBed, On tHe SurfAces Of solder, or compONentS to be bonded, such as an insUlatoR sUBstrATe, Or tin Oxide on SUrFACes Of ThE soLdER, cOpper OxiDe on surFaces of copPer PaTtern or metal BAsE (i.e., copper), nIckEl oxide on surFacEs of niCkEl pLAting ForMed on SurfacES of the Copper patTeRN and meTAl patteRN Or The lIke, are reduced, and H2o PrODuced thereby is GasifiEd ANd REMaiNs iN the voids. ANoTher cAUse is thAT gASSEs gENerated by the fLux vaporizaTIon Also caN fOrm VOids. MoReoveR, tHE flUx itself remAiniNg in the soLder boNDed layeR Can form Voids.
THerEfoRe, to REdUcE voIdS In tHE sOldER boNded layeR, tHe SurfaCes oF THE CompOneNts tO be boNded need to be fRee Of oxIDizAtion To keeP the SuRface Clean, tHe solDeR materials need tO be fRee of dissOlvEd Gas, AnD the sOLder maTerIalS need to Have gooD WetTiNG ABiLity. Moreover, it is deSiRABlE to optimIze the SOlDeRIng profiLe, To cOntrOL DeforMatiON oF componeNts to bE BoNdEd, and to CaRry out SoLdeRinG in a dEPresSurizeD atmosphEre.
In THis regard, there HAve been a numbeR Of PROpOSals To iMprove the soLderINg teChniQUe. for EXamplE, JP-A-11-154785 dIsCLoSEs a method in which solDeRing is Done iNside a sealed vEssel contaININg an atmoSpheRE oF Gas having a highEr theRmal conducTIvity thaN that Of the air, While reduCINg pressuRe pRioR to HeaTINg And melting of tHE SoldEr, And incrEasIng the pResSurE hiGheR tHan the priOr pressuRe BeFoRe The SoldeR Is solidiFiEd. IN tHis MethoD, Voids aRe comPresSeD dURinG solidiFIcATIon tO rEdUce tHeiR vOlumeS.
In aDDitIon, JP-A-779071 dIscloses a MetHOd in WhIcH solder Is provided on a SuBstrate and ElEctRonic pARTs are temPorarily mounted on the solDEr sectiOns BeforE the Solder is hEatEd and mEltED under An atmoSpherE oF a vACUum to SOLdEr tHe Electronic PARts. here, hOwEver, No reducTion gas, such as hydroGEn gAs, is used.
MoreoVer, jP-A-11-186331 dISClOseS A mEThoD oF ManUFActuring a semicoNductor devIcE, WhEre an insulATor SuBstrate Having a ConduCTor layeR on a metal Base is solDeR bonDED anD a semicondUctor chiP is mounteD On the INsUlatoR suBstratE. THe sOlder BondinG Is aChievEd by meLtIng solDer unDeR an atmosPheric pressure to form melTed solDer, reDucIng the atmOspHEriC pressure On thE melted solDer, RetUrninG thE PressUre oN ThE meLTed soLder TO the atmosPHeRic PREsSure, and soliDIFYinG the mEltED soldeR. WhiLe this method appliES a vacuum operatIon dURIng SolDEr boNdIng using a flux, nO reFeRENce is madE aBout using hyDrogen or A rEDucinG atmosPhere.
FUrthermORE, Jp
 cause is that, during sol dering, ma teria lsads or bed,  onthe surfaces o f  sol der, or components tobe bo nd e d, s u ch  as a n insul a to r sub st ra te,  o r  t in ox ide  on sur faces of t heso lder, copper ox ide on sur fac es of copper  pa tternor  me t al ba se(i.e. , copp e r), ni ckel oxid eo n surf a ces ofn i ck el p lating formed ons ur f aces of the co pper p at t er n and  me tal patter nor th e  like,a re r e duc e d, and H2O pr oduced ther e byis gas if ied and re mains  i n  th e voids. An othe r cause i s that gassesg enerate d by t heflu x va p or iz ati on als o  c anf orm  voids.Mo re over,  the f l u x it sel f re maini ng in the sol der  bon d edlayer  canform  v oids. 
There fore,  t o reduce voidsin t he solder  bo nd edla yer,t he sur fac esof thecompone n tsto b e  b onded need to be f re e of  oxidiza tion t o  k ee p  the sur fa ceclea n ,  thesold e rmaterial s need to  b e freeof  disso lv edgas , and thesolder  materia ls ne e d to have good wetting abili t y. M or e over , i t is desira blet o op timi z ethe solde ringpr o fi l e, to control defor ma tion o f com ponents to be  bonded, a n d to carry  out so l dering in a de press urized atm o sphere.In th is regar d, thereh a ve beena n umb erofp r op osals to impr o v e th esolderi ngtechniq ue.  Fo r e xam pl e, JP-A-1 1-154785  d is cl os esa met h od in wh ic h s ol der ing i s  doneinsid e ase al e d v essel c o nt a i ning  a natmo sph er e ofgash avi ng a hi gher ther mal cond uc ti vity th an that of th eair, while  r edu cing p r e ssure pr ior to heating and melt i ng of t hesolde r, a nd increa sin g thepre s sure h igherthanth e p r i or pr e s su rebe fore the s o l der  is s ol idif ied. In  this method, void s  ar e compresseddur ings o li dif i ca t ion  t o  re d u ce their volume s.
In addi ti o n,  JP-A-7790 7 1 d is closesa metho d inw hich so lder is p rovided o na su b s tra te and ele ctronicparts are tempo r ar ily m oun ted on  t hesolde r sect i ons  befo re the  s olderis he at ed and m elted under an atmosphe re ofa vac uum  to solde r t h e e lectronic  par ts. Here,how eve r, no  re d uctio n ga s ,suc h  as h ydro g en gas, i s  u sed . Mo reover, JP- A - 1 1-1 86331  di s closes  a m ethod of manufact u ring a semicon duct o r  de vic e , wh er e an insulator  su bs t r ate havi ng  a conducto r layeron a met al bas e is s older b o n de d  and a  sem ico nductor c hip  i s  mounte don the in sula to r subs trate. Thes o lder bonding isachie v e d bym elt ing s ol der und e r an  atmospher ic pressure  to fo rm m elted  solder ,reduci ngth e atmosphe r ic pressu re on  the me lt ed s old er, re turn i n g the  pre ss ure  on the m e l te d  s ol d erto t he at mo sphe ric press u re, andsol i difying  t hem e lted s o ld e r . While th ismetho d applies av acuu m  o p erati on dur ing so lder bo n din gusing a  fl u x , no refe rence ism ade  a bout  using h yd roge norareducing atmosp here.
Fu rthermor e ,  JP
 cause_is that,_during soldering, materials adsorbed,_on the_surfaces_of solder,_or_components to be_bonded, such as_an insulator substrate, or_tin oxide on_surfaces_of the solder, copper oxide on surfaces of copper pattern or metal base (i.e.,_copper),_nickel oxide_on_surfaces_of nickel plating formed on_surfaces of the copper pattern_and metal_pattern or the like, are reduced, and H2O_produced_thereby is gasified_and remains in the voids. Another cause is that_gasses generated by the flux vaporization_also can form_voids._Moreover,_the flux itself remaining_in the solder bonded layer can_form voids.
Therefore, to reduce voids in_the solder bonded layer, the surfaces of_the components to be bonded need_to be free of oxidization_to keep_the surface clean, the solder_materials need to_be free_of dissolved gas,_and the solder materials need to_have good wetting_ability. Moreover, it is desirable to_optimize_the soldering profile,_to_control_deformation of_components to be_bonded,_and to_carry_out soldering in a depressurized atmosphere.
In_this_regard, there have been a number of_proposals to improve the_soldering_technique. For example, JP-A-11-154785_discloses a method in which_soldering is done inside a sealed_vessel containing_an atmosphere_of gas having a higher thermal conductivity than that of the_air, while reducing pressure prior to_heating and melting of_the solder,_and_increasing the pressure_higher_than the_prior pressure before the solder is solidified._In this_method, voids are compressed during solidification_to reduce their volumes.
In_addition,_JP-A-779071 discloses a method in which_solder is provided on a substrate_and electronic parts are temporarily_mounted_on_the solder sections before the_solder is heated and melted under_an atmosphere of_a vacuum to solder the electronic parts._Here,_however, no reduction gas, such as_hydrogen_gas, is used.
Moreover, JP-A-11-186331 discloses a_method_of_manufacturing a semiconductor device, where_an insulator substrate having a conductor_layer on a metal base is solder bonded and_a semiconductor chip_is mounted on the insulator_substrate._The_solder bonding is achieved by melting solder under an atmospheric_pressure to_form melted solder,_reducing the atmospheric pressure on the melted solder, returning the_pressure on the melted solder to the_atmospheric pressure, and solidifying the melted solder. While this method applies_a vacuum operation during solder bonding using a_flux, no reference is made about using_hydrogen or a reducing_atmosphere.
Furthermore,_JP