There is no lead to weld: There is not lead to make.
This text describe how begin and have lead produce, measure technology course and act as the essential change to the whole technology. . . . There is no lead to make( Lead-Free Manufacturing)
Do not have lead technology to one, must set about several kinds of consideration , must set up certain condition . First of all, some equipment selects and different material can improve the technology , these must be gotten ready before beginning to have no lead to weld. For example, in the crest weld , the soldering tin must be changed.
(Reflow Soldering Equipment)
Secondly, begin not to have a good plan of technological requirement of lead, the key problem must be put forward, If" what may we meet to weld the defect? "" it is and not standard in that refuse not to accept it is something? "and"in allowing among soldering tins what levelses 's pollution it is? " the backset current welds the equipment (Reflow Soldering Equipment)
Help the solder flux to flow to manage
In having lead in welding, have lead soldering tin to influence technology temperature and influence and heat temperature curve by backset current. Because relatively high temperature and different tin lotion chemical composition, in welding, Different remaining things will be evaporated . For whether relatively a low one maintain and shut down time keep the cleanness’s of machine, need one a piece of proper helping solder flux flow the administrative systems. This system must not (one picture).
Picture one. Management of helping the solder flux to flow prevent the pollution from entering cooling area
The controlled one cool and reach the temperature curve optimized.
In having lead recommend one a piece of controlled system of colorings in welding, because as soon as the stove has proper ability, Temperature can all be defined in time for above liquefaction, the coming out of crystalline grain structure and board. Need more room temperature fans naturally. Give a recommendation use one a piece of advanced direct air, totally integrateds, arrange the hot system. This system is designed and used for consume sing and offers good cooling with the relatively low nitrogen. At recycling distilled water and the mixtures of alcohol cool third two this system. The friendly mixture of this kind of environment does not require frequent changing .
(Wave Soldering Materials and Equipment)
The treatment of the board
Because the relatively high temperature in the stove , the board is inclined to warping. The strut that can install the board in the stove keeps the board levelling even more, the result reduces the defect . Welding material of crest and equipment (Wave Soldering Materials and Equipment)
Preheat and optimize
Because of relatively high technology temperature, there is not lead that weld the request with helping the solder flux different from lead-bearing soldering tin . Help solder flux finish determining each preheat and dispose and suitable for this technology most by type. Use water as and help solder flux solvent and give a recommendation at one a kind of quartz excellent heaterses at preheating area heat board rapidly. At second and districts, force convection heat module come with each.
Choose each have fast to vary and dispose the crests of flexibility weld the machine. Preheat module is should have been easy to exchange in order to finding. ( picture two)
Picture two, preheat and settle the technology of optimizing flexibly
The soldering tin changes
In order to having and replace for alloys for lead tins /lead alloys require not only discharge and fulled of more pan for less than soldering tin again. All lead must be removed from the soldering tin pan completly. Any plumbous remaining things and pollute having lead alloy that left, thus go beyond the specification range. Consider most heavy allows lead-bearing to measure exceeding 0 . 2%. Take every caution against error while changing the alloy.
The procedure that the soldering tin changes must be strictlied observe. First of all,in tins pans tins /discharge clean at lead soldering tins . Collect the case to collect the soldering tin availably. Because pan to design and have special Rong Shi come and help and keep steady soldering tin wave most tins, This kind of job is quite difficult and labour intensity is great.
As soon as the tin pan becomes empty, must load with the pure tin . Tin pan, including all supplementary parts and surface, must erode completely with the tin . Later, will discharge the tin out. At last, may melt and have no soldering tin of lead
Systematic control software adjust, in order to preventing any in impeller from damage. Especially, the temperature of starting of the impeller must be improved, otherwise may be rotated in the impeller when not totally melt ing of soldering tin .
Come and substitute tin of new tin pan at another kind of methods /plumbous tin pan. A merit of exchanging the tin pan is, the tin pan that the tin is plumbous can also be exchanged back, A part as the action plan out of control. In addition, tin stay and use in and have product who lead weld also by plumbous tin pan.
Still have no thing issued, speak of it about having plumbous practical experience, With new-type to have lead not to be compatible at special problems alloy material, these issue further keeps forging ahead sometimes. At present what we know , have lead the high tin contents of alloy, Use in the stainless steels of part use again at 304 one tin, because these part in having lead produce odd months will be damaged often while being alike.
Weld the parts of machine change direction each anticorrosive 316 stainless steel. The material enough to use for and weld speed low those a pot of parts reliable. To other parts, but use and use a kind of special anticorrosive coating on SS 316 and impeller ( picture three). It uses titanium it makes those the parts of extreme condition with stainless steel reasons very much high cost, And make the engineering level that expect very much of these special parts with the titanium
Picture three, comparison of the impeller: Having tin copper the impellers of soldering tin after the production on the left one half a year One applies the impeller applied specially on the right It is first-selected that this kind of dyke corrodes the coating because but not a kind of ceramic coating, because of its superior( 2000 Vickerses of ¡À). Not like the ceramic coating, the special coating will not be damaged because of safeguarding because of carelessness once in a while. Merits , because the coating smooth surface, soldering tin glue and enclose the metal , This makes anies part with coating all very apt to be cleaned.
To the tin pan, use the steel, because of its superior. One kind hinder hot coating and prevent the iron from melting into in the soldering tin. We notice , the melting rate in having lead alloy of iron is decided by the following factor : ¡¤Material uses that use have lead alloy No. ¡¤
The level of pollution
It is the alike at traditional tin /weld because technology the same, dissolve a lot of metals at leads. This piece dissolve speed decide by host material,, and soldering tin flow speed temperature soldering tin composition soldering tin. The speed of dissolving of a kind of special metal is relatively low, if this metal appears in having soldering tin of lead. For having no soldering tin of lead, three pieces of main pollution are lead, copper and iron.
When the following one year, will use and have no tin of Korea S. of lead , but the surface coating to the component and board is lead-bearing. As a result, contain the anies of bismuth have lead absorb the lead from surface coating by alloy, Cause different points of the soldering tin .
Picture four, 1.5%s one that leads pollute tins /the results of the soldering tin silver Another example, picture four shows that one kind is received 1. 5%s that the lead pollute for tin /silver for alloy. However, originally alloy rise to" new" tin at the points of the C &-#176; 179 /lead /silver the - 218s of the alloy 211 &-#176; C range
The pollution of the copper
The tall tin alloy absorbs the copper more rapidly than the low tin alloy, the quantity of copper in having lead alloy determines how much copper will be dissolved. Tin /lead technology, it know we 0. 2% or high copper content lead to the fact such as tin problem who bridge increase. At tin /among leads from 0. 3%.
This one is 0.3%s it is it is at some for tin /the silver in the present regulations of the alloy is the heaviest. At tin /silver high for tin content in of alloy (96. 5%) cause during production level quite fast increase, especially not at countless copper the boards of pads of having copper content. Some technologies will go beyond the specification after four five months. At tin /leads crests while welding, we cannot /isolate copper of at leases, remove it. It is the unfortunate, in having, while welding, change soldering tin of we at leads.
It is for tin /silver /copper alloy, it is the situations. First of all, this kind of alloy has already contained the copper, so copper is drawn relatively slow. However, it test show it is with 1% or more copper by tin /silver /draw copper of no longer at copper alloys. The copper is steady in 1% of the levels.
The pollution of the iron
Irons at tin /lead of dissolve speed low. With not having plumbers alloy, the quantity is higher than 10 times of factors probably. Such as, among one piece factories, tin /silver /bismuth /on one years for 0.002% of the irons.
General, each have lead weld technology pollution of involving by crest. First of all, use and have lead check the chemical compositions of alloy often by the companies of soldering tin. After about one year, it has been steady how much they have discovered the pollution. If also within their specification, length of the intervals controlling the size increases level metal.
By contrast, there are real concerns to the pollution of soldering tin in other technologies . It use somes by tins /weld silver alloys,the alloys to drawing copper getting more sensitive very. Go beyond specification run and let these company look for substitute continuously.
There are thes question left, what level of pollution is allowed? Because the change of the chemical composition of alloy, melt and name a person for a particular job to drift about, Melting the range will increase. Sometimes,the new point of different alloy that will appear in the soldering tin (picture four).
Weld the defect (Soldering Defects)
In having lead in welding, take place the defects of special envoys and weld foot finish mentioning and tin need( tin whisker). But other defects at the cavities of solder joint, seem that technology take place and many lead than tin too. Up to today, do not have it to having international standard of the defect in plumbous pad, This make and define what acceptable and further more difficult.
Weld the foot to raise
It welds foot it raises to be stage of cooling weld round feet from electroplating coherent hole( PTH, plated through hole)s copper the a kind of separations of pad. It is chemical compound of alloy, copper pad, the board thickness and temperature coefficient of expansion of the board material to weld the main reason why the foot raises (CTE, Coefficient of thermal expasion) mismatch. Weld foot raise and take place. It but weld feet last at other alloys, tins toos /watch coppers. Though can estimate the dependability of the pad is reduced, but temperature circulation test and still show that it is good in most situations. Tin /silver /bismuth /antimonies solder joints it is the fine since there is very intensities, and show by circulation temperature. However, it has lead weld standard who electron assemble in addition, company as much as a lot of accept and weld foot raise at their product.
The quantity of cavity happening in having technology of welding of lead is increasing , especially when there is not VOC to help the solder flux to use water base . The empty diameter range is from 10 ¦Ì ms - 1 mm. General, how empty to influence the dependability of the pad ly. But, the large cavity may be reduced and resist the intensity of splitting. The cavity might decrease electric conduction of the circuit of the interconnection and heat conduction performance , cause hotly to lose efficiency.
There is much more in the reason formed in cavity. The cavity may be the result that the soldering tin shrinks during the solidification. The ones that electroplated open hole in welding may emerge in the cavity in the soldering tin to exhaust. In addition, the cavity may be a moist result that is not enough for of pad.
The surface attack easy to be increased by the natural crystal of pure tin. These crystal (tin must) very 0. The diameter of 1 - 5 ¦Ì ms, it is several mom’s long that can rise to. The tin or even begins to increase after a few years after electroplating. Because its size and different form, the tin may cause the short circuit.
The tin must increase and depend on the temperature and humidity . Key temperature is above 50 &-#176; Cs, relative humidity 50%. For musting avoid the tin, the temperature stress introduced in welding the technology should be low to the best of one's ability; This is to adopt another reason intensifying the curve of backset current sharply. In addition, the content of the tin is very important; The higher the level of purity of tin is, the greater the chance that must form the tin is.
The beginning of production (Production Start-up)
Before being can be analysed to have any data, must do measurement . It is important the characteristic ization to the machine of these procedures and regulate. Need to collect the good data, in order to obtain useful analysis. You can distinguish the variable( the measurement data with the unit) and characteristic ( the data counting).
The backset current is welded
The backset current is welded Write down parameters in variable including machine and data in the technology of backset current. The machine parameter includes the speed of the conveying belt, heating area temperature, temperature of cooling the unit and water temperature district.
Write down include at parameter and reach and consult the times of temperature of at datas, Consult the time, average temperature, minimum slope . Characteristic refer to weld defect is at cavity, jump and weld ,, and component erect bridge tin ball tin.
Raise qualification rate and reduce machine shut down time in having lead weld goal that must reach after leading into. After beginning not to have lead technology, will set up a technology of repeatable measurement hard , Each finish calculating technology ability and one use this datum to regulate the machine method the methods of value rationally.
To most companies, 6 Ò is an" inconceivable" word. These 6Ò equals 2 of the Cp value; 0. 002 of the a million every part( ppm, per million of parts) defect s are counted . In counting, if Cp =1, it is capable that a technology is. But, this Cp value defect level equivalent to 2700 ppms. Because of this figure being quite high, some other companies consider Cp =1. 33 is regarded as goal value. This figure defect level equivalent to 64 ppms.
The regulating of backset current machine
One a piece of reliable school quasi orderings require measurement one a yuan of suitable PCBs. However, board to use FR - 4 as and regulate measurement, because glass transform value in each drop after running temperature( Tg) by attitude; And these board at warping of having lead manily high temperature. In addition, may take place and take off layer after a lot of circulation of backset current.
As a result, the electric thermocouple installed in FR - 4 regulates the board may be taken off loose, it is the gas temperature measurement, But not the material temperature of the board. From stove being that hall pass to compose music line receive reliable result and better datum with sensor equipment. The tools used for regulating the technology must be regulated regularly.
Don't use the high temperature glue to brings and joins the electric thermocouple. The precision of having 5 &-#176; Cs of ¡Oaf electric thermocouple joined with Kapton sticky tape , depend on the operator's technology very much. Or resin get soldering tin continuously and the precisions of C 1 &-#176; ¡À unanimous result high temperature.
The crest is welded
In the crest welds , an important difference exists in the computer and data write down parameters. Machine parameter including conveying belt speed, temperature of preheater and temperature of welding . Write down at datas parameters including temperatures slopes ( the heaviest with minimum), average slope, maximum temperatures, ¦¤ T, stay and last time( for slices of wave and main wave) in crestses , Keep in touch with the length , with parallel degree and soaking the degree of depth in in the tin and wave of the crest .
In order to verify the quantity which helps the solder flux, must define a procedure . Characteristic include weld defect is at cavity, jump , coherent holes pack, weld tin foot raise.
The regulating of welder welding machine of crest
In the same statistical method who backset current use in welding being can have been with welding with the crest. It regulates to be must have been with designing and use for equipment who crest weld go on. Commerce can measure contact time and preheat in the temperature curve to have the tool that can be bought. In addition, help can at water quick papers or glass plate check performance solder flux. Would rather each accurate verification method manufacturers, measure use do and helping the quantity of the solder flux at one a piece of accurate balance veries