Remove the method for chip and plumbum-stannum alloy bump surface welding-assistant
Technical field
The present invention relates to semiconductor packing process, specifically, relate to a kind of method of removing chip and plumbum-stannum alloy bump surface welding-assistant.
Background technology
Along with the continuous development of integrated circuit technique, electronic product more and more develops to miniaturization, intellectuality, high-performance, high reliability direction.Progressively dwindle at the ic core chip size, under the situation that integrated level improves constantly, electronics industry has proposed more and more higher requirement to the integrated circuit encapsulation technology.
Flip-chip (flip chip) technology is the soldered ball that forms by at chip surface, the chip upset is formed with base plate to be connected, thereby reduce package dimension, satisfy the high-performance (as high speed, high frequency, littler pin) of electronic product, the requirement of little profile, make product have good electric property and heat transfer property.
Stud bump making technology (bump) is a key technology in the flip-chip.Salient point be scolder by certain process deposits on the chip interconnecting metal layer, the metal soldered ball that reflux to form through uniform temperature.In the manufacture craft of lead and tin alloy protruding point, before the stud bump making, as shown in Figure 1, chip 10 has formed passivation layer 11 and interconnecting metal layer 12, enter after the stud bump making, at first chip surface form a ubm layer 13 (Under-Bump Metallurgy, UBM); On the UBM layer, spray photoresist then, and expose, develop to form the photoresist opening; Then in photoresist opening part deposit lead tin alloy solder 16; Afterwards, remove photoresist layer and part ubm layer 13.
With reference to figure 2, in chip surface spraying scaling powder (not shown), then wiping solder 16 refluxes and forms lead and tin alloy protruding point 17 at a certain temperature, subsequently, removes the scaling powder on chip 10 surfaces and the lead and tin alloy protruding point 17.During the spraying scaling powder, scaling powder should cover the whole surface of chip and wiping solder, plays the effect that auxiliary wiping solder refluxes.
Scaling powder commonly used at present has two major types, the first kind is an organic solvent type, the characteristics of the type are that the bioactive agent composition in the scaling powder all must be dissolved in the organic solvent (as methyl alcohol, ethanol, propyl alcohol), this scaling powder store and use in, have inflammable, volatilization, contaminated air, problems such as pungent.Therefore, consideration for environmental protection and safety, a lot of companies use the second class water base type scaling powder, though the scaling powder of the type has advantage from environmental protection and secure context, but after shortcoming is to use such scaling powder, therefore the residue that residues in panel must clean because the moisture-sensitive dissolving causes insulating properties to descend.
Chinese patent application 02807547 has proposed a kind of problem of using no-clean scaling powder to solve welding assisted agent residuals, technical scheme is to spray scaling powder on the chip that contains the salient point scolder, reflux then, the reflux temperature of salient point scolder is greater than or equal to the volatilization temperature of scaling powder.Described scaling powder is so long as at 200 degrees centigrade of hydroxy acids that can seethe with excitement down.But this method need adopt the pulse heating tool heating that refluxes, and need carry out strict control to the thermograde that refluxes, and not only cost is higher on commercial Application, and implements also relatively difficulty.
At present in the commercial Application extensive use remain water base type scaling powder.Prior art mainly is to utilize deflux to remove backflow chip and the residual scaling powder of plumbum-stannum alloy bump surface afterwards.After using deflux to clean to reflux on chip and the lead and tin alloy protruding point during residual scaling powder, it is coarse to find that the surface of lead and tin alloy protruding point can become, and causes chip eclipsed defective to occur.As shown in Figure 3, of the present invention eclipsed, be meant because the coarse aberration that causes chip surface to occur of plumbum-stannum alloy bump surface.
Therefore, need that a kind of technology is simple, cost is lower, the method for the residual scaling powder of chip and plumbum-stannum alloy bump surface after the removing wiping solder that can carry out commercial Application in manufacture of semiconductor refluxes.
Summary of the invention
The problem that the present invention solves be the available technology adopting deflux remove wiping solder reflux after during the residual scaling powder of chip and plumbum-stannum alloy bump surface, can make coarse that plumbum-stannum alloy bump surface becomes, thereby cause chip to produce eclipsed defective.
For addressing the above problem, the invention provides a kind of method of removing chip and plumbum-stannum alloy bump surface welding-assistant, comprise the steps: to use water base cleaning reagent to clean chip and lead and tin alloy protruding point; Use deflux to clean chip and lead and tin alloy protruding point, remove residual flux.
Described water base cleaning reagent is a deionized water.
The consumption of described deionized water is 15L to 20L.
When using water base cleaning reagent to clean chip and lead and tin alloy protruding point, wash 90% to 95% of residual flux total amount on chip and the lead and tin alloy protruding point.
The time of using deflux to clean chip and lead and tin alloy protruding point is 15 minutes to 45 minutes.
Described deflux is the pH value at 8.5 to 11 deflux.
Described deflux is the CLEANTHROUGH series 750H deflux that Japanese Kao company (KAO) produces, perhaps the MICRONOX series MX2302 deflux of the Kyzen of Nashville company production.
Compared with prior art, the present invention has the following advantages:
1, at first adopt water base cleaning reagent that chip after the salient point solder reflow and the residual scaling powder of plumbum-stannum alloy bump surface are cleaned, can effectively remove the scaling powder of chip surface and wiping solder head portion earlier, after the cleaning, chip and plumbum-stannum alloy bump surface be the scaling powder of residual small part only, adopt conventional deflux to clean then, the weak corrosion that the interaction partners plumbum-stannum alloy bump surface causes between deflux and the scaling powder when avoiding directly using deflux to clean in the prior art, thereby the smooth surface of obtaining, the lead and tin alloy protruding point that the terne metal surface is not corroded.
2, adopt weakly alkaline deflux to clean, can clean chip and the remaining a small amount of faintly acid scaling powder of plumbum-stannum alloy bump surface afterwards by the water base cleaning reagent of more effective removing, the better protection lead and tin alloy protruding point is not corroded.
3, the method for removing chip provided by the invention and plumbum-stannum alloy bump surface welding-assistant, technology is simple, and the requirement of operating equipment is not wanted, and is fit to use on the production line.
Description of drawings
Fig. 1 is that prior art is removed the cross section structure schematic diagram of wiping solder on chip after photoresist and the ubm layer
Fig. 2 is the cross section structure schematic diagram after prior art terne metal lead and tin alloy protruding point refluxes
Fig. 3 is that the prior art deflux cleans the eclipsed picture of chip surface after the scaling powder of chip surface
Fig. 4 is the shape appearance figure that the prior art deflux cleans terne metal plumbum-stannum alloy bump surface after the scaling powder of chip surface
Fig. 5 is the shape appearance figure that the prior art deflux cleans terne metal plumbum-stannum alloy bump surface after the scaling powder of chip surface
Fig. 6 is that the prior art deflux cleans the microscopic appearance figure after the terne metal plumbum-stannum alloy bump surface amplifies after the scaling powder of chip surface
Fig. 7 is a process chart of avoiding the coarse method of plumbum-stannum alloy bump surface provided by the invention
Fig. 8 adopts method provided by the invention to clean the shape appearance figure of terne metal plumbum-stannum alloy bump surface after the scaling powder of chip surface
Fig. 9 adopts method provided by the invention to clean the shape appearance figure of terne metal plumbum-stannum alloy bump surface after the scaling powder of chip surface
The specific embodiment
At the technology used in the present invention and method, the specific embodiment of the present invention is done a detailed explanation below in conjunction with specific embodiment.
Before salient point solder reflow processing procedure, often use water base type scaling powder.The main component of existing water base type scaling powder comprises water-soluble resin, activator and solvent.Wherein said water-soluble resin mainly is to be selected from polyvinyl alcohol, water soluble acrylic resin, water soluble alkyd resin, water-soluble epoxy resin or two kinds or above mixture in them.Described activator is made up of surfactant, organic acid and co-solvent, and described surfactant is to be selected from succinic acid two ester sodium sulfonate, aerosol OT or their mixture; Described organic acid is to be selected from salicylic acid, acetate or their mixture, and described co-solvent is glycerine, 2-methylpentane-2,4 glycol.Described solvent is a deionized water.
Above-mentioned scaling powder is an acid reagent, and the pH value generally between 2 to 5, before wiping solder refluxes, is sprayed on the surface of chip and wiping solder with it, can't cause damage to chip and wiping solder.After the wiping solder backflow, because the high temperature action of reflux course, scaling powder is softening to be in a liquid state.After the cooling, scaling powder can solidify and become thicker scaling powder layer at the chip and the plumbum-stannum alloy bump surface that forms that refluxes.Because scaling powder is an insulating materials, the thicker scaling powder layer that liquid scaling powder cooling back forms can make the lead and tin alloy protruding point contact resistance increase, thereby cause the lead and tin alloy protruding point poor electric conductivity that forms, can't satisfy the requirement of application, so this layer scaling powder layer must be removed.
The general direct use deflux of prior art is removed the scaling powder layer that above-mentioned wiping solder refluxes and forms at chip surface afterwards, the various commercially available deflux that described deflux is used always for those skilled in the art, as the CLEANTHROUGH series 750H deflux of Japanese Kao company (KAO) production, the perhaps serial MX2302 deflux of the MICRONOX of the Kyzen of Nashville company production.
In the prior art, use above-mentioned deflux to remove after the scaling powder that forms on the chip after the salient point solder reflow, it is coarse to find that lead and tin alloy protruding point becomes, thereby causes occurring on the chip eclipsed phenomenon as shown in Figure 3.Fig. 3 is that the light microscope by routine detects and obtains.
Fig. 4 and Fig. 5 have provided the surface topography map that directly uses above-mentioned deflux to remove lead and tin alloy protruding point after the scaling powder layer that forms on the chip after the lead and tin alloy protruding point solder reflow in the prior art respectively, as can be seen from the figure, the surface of lead and tin alloy protruding point does not have metallic luster, and this causes owing to lead and tin alloy protruding point is more coarse.Fig. 4 and Fig. 5 are that the light microscope by routine detects and obtains.
As shown in Figure 6, for amplifying 500 times, the light microscope by routine detects the plumbum-stannum alloy bump surface shape appearance figure that obtains afterwards.Can find out clearly that from figure the terne metal plumbum-stannum alloy bump surface is rough and uneven in surface, and produce the corrosion product that is different from the terne metal matrix.
Do not wish to be confined to Theory Influence, but a kind of possible theoretical explanation is: use in the prior art deflux cleaning scaling powder residual after, the more coarse this phenomenon that plumbum-stannum alloy bump surface becomes may be the generation because the terne metal that causes plumbum-stannum alloy bump surface of interacting between deflux and the scaling powder is corroded.When using deflux to remove the residual scaling powder of chip and plumbum-stannum alloy bump surface, between deflux and the scaling powder chemical reaction and physical solution take place in, the temperature of chip and plumbum-stannum alloy bump surface raises, therefore cause lead and tin alloy protruding point to be more prone to be subjected to the invasion and attack of corrosive ion in the solution, weak corrosion takes place.Above-mentioned theory only is a kind of possible explanation, and the present invention does not wish to be confined to the influence of above-mentioned theory.
For addressing the above problem, the invention provides a kind of remove lead and tin alloy protruding point reflux after the method for chip and plumbum-stannum alloy bump surface welding-assistant, with reference to technological process shown in Figure 7, use water base cleaning reagent to clean earlier, remove chip and the residual part scaling powder of plumbum-stannum alloy bump surface, re-use conventional deflux and clean, remove chip and all residual scaling powders of lead and tin alloy protruding point.
Among the present invention, described scaling powder can be the water base type scaling powder of pH value between 2 to 5 that is applicable to lead and tin alloy protruding point backflow processing procedure known to the technical staff in the semiconductor packing process, as KESTERPASTE FLUX (TSF 6807) scaling powder released of Kester (Kester) sales department that is subordinate to U.S. N orthrop grumman military project group, its main component is resin and 2-methylpentane-2,4 glycol.
Cleaning the described residual used water base cleaning reagent of scaling powder is deionized water, what the present invention adopted the use of washed with de-ionized water scaling powder is the common hydraulic giant that those skilled in the art are familiar with, the hydraulic pressure during to injection and the consumption of deionized water do not have strict restriction yet, in general, washing 90% to 95% of scaling powder total amount residual on the chip gets final product.
As a kind of optimized technical scheme, adopt common hydraulic giant, adjust hydraulic pressure (1psi equals 6.89kPa) between 40 to 50psi, when the consumption of employed deionized water is 15L to 20L, can reach wash lead and tin alloy protruding point reflux after the purpose of residual 90 to 95% defluxs of chip surface.
Use after the washed with de-ionized water, deflux of the present invention can be to clean the lead and tin alloy protruding point backflow conventional deflux of chip surface scaling powder afterwards in the prior art.In a specific embodiment, chip is immersed the container of filling deflux, clean 15 minutes to 45 minutes (min) afterwards, can remove chip and the residual scaling powder of plumbum-stannum alloy bump surface fully.
Technical scheme as a kind of comparative optimization, use after the washed with de-ionized water, the present invention adopts the pH value to clean chip and the still residual scaling powder of plumbum-stannum alloy bump surface at 8.5 to 11 weakly alkaline deflux, as the CLEANTHROUGH series 750H deflux of Japanese Kao company (KAO) production, the perhaps serial MX2302 deflux of the MICRONOX of the Kyzen of Nashville company production.Weakly alkaline deflux can more effective removing chip and the still residual a small amount of scaling powder of plumbum-stannum alloy bump surface.
Adopt method provided by the invention can dispose lead and tin alloy protruding point backflow chip and the residual scaling powder of plumbum-stannum alloy bump surface afterwards fully, lead and tin alloy protruding point can not produce the defective of roughening.
In a full implementation example of the present invention, at first adopt washed with de-ionized water to fall the scaling powder of chip surface, the consumption of used deionized water is 18L, the pressure of the hydraulic giant that is adopted is 45Psi, and then chip is immersed MICRONOX series MX2302 deflux solution, cleans the scaling powder that 30min can remove chip surface afterwards fully, observe the surface of lead and tin alloy protruding point, as Fig. 8 and shown in Figure 9, bump surface is smooth, and the terne metal surface is not corroded.
The present invention at first adopts water base cleaning reagent that chip after the salient point solder reflow and the residual scaling powder of plumbum-stannum alloy bump surface are cleaned, remove the scaling powder of chip surface and wiping solder head portion 90 to 95%, when adopting conventional deflux to clean again, because the scaling powder that chip surface and terne metal contain seldom, even scaling powder and deflux interact and react, can be owing to reaction forms local hot environment yet, thereby avoid the phenomenon of weak corrosion that plumbum-stannum alloy bump surface is caused, obtain smooth surface, the lead and tin alloy protruding point that the terne metal surface is not corroded.
Though oneself discloses the present invention as above with preferred embodiment, the present invention is defined in this.Any those skilled in the art without departing from the spirit and scope of the present invention, all can do various changes and modification, so protection scope of the present invention should be as the criterion with claim institute restricted portion.