CN103384448A - Printed circuit board and method for processing surface of printed circuit board - Google Patents
Printed circuit board and method for processing surface of printed circuit board Download PDFInfo
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- CN103384448A CN103384448A CN2013102621115A CN201310262111A CN103384448A CN 103384448 A CN103384448 A CN 103384448A CN 2013102621115 A CN2013102621115 A CN 2013102621115A CN 201310262111 A CN201310262111 A CN 201310262111A CN 103384448 A CN103384448 A CN 103384448A
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Abstract
The invention discloses a method for processing the surface of a printed circuit board. The method comprises the steps that the printed circuit board is provided, the printed circuit board comprises a printed circuit board substrate and a brazing disc formed on the printed circuit board substrate, welding resistance processing and anti-plating processing are conducted on zones outside the brazing disc on the printed circuit board substrate; micro-etching is conducted on the brazing disc; a cobalt-based metal layer is formed on the surface of the brazing disc which undergoes micro-etching and the cobalt-based metal layer is used for directly making contact with lead-free solder, and the printed circuit board with the cobalt-based metal layer is cleaned and dried. The invention further provides the printed circuit board which undergoes the processes.
Description
Technical field
The present invention relates in the microelectronics Packaging field, a kind of printed circuit board (PCB) (PCB) for encapsulation and surface treatment method.
Background technology
In the microelectronics Packaging field, the pad on PCB or terminal part, the component hole that insertion element is used and printed contact partly wait except as welding, the element of also seeking line bonding etc. connect and with the conducting that contacts of connector.Therefore in order to ensure this part the weldability of copper, connection reliability and contact reliability and the various processing carried out are called final surface treatment (Final Finish) or surface treatment (Surface Finish).
The surface treatment of existing PCB mainly contains 4 kinds of methods, and being respectively has organizational security weldering film to process, and tin system processes, and gold system processes (chemical nickel plating/soak gold) and electrosilvering.Wherein, gold is that processing is to use more PCB surface treatment method, and comprises electrogilding, chemical gilding and immersion gold plating (soaking gold).But, in industrial production, consider cost, usually by carrying out selective electroplating to reduce the use of gold.In addition, because gold is that the processing procedure control ratio is more difficult, have the problems such as black dish, and the gold layer is generally thinner, after lead-free solder and the welding of Ni-based thin film metal layer, is easy to forming at the interface Ni
3P(nickel three phosphorus) layer, also can cause solder joint to lose efficacy under cycling hot, electricity, mechanism, thereby affect the reliability of lead-free solder solder joint.
Under this background, in order to reduce costs and improve the reliability of lead-free solder solder joint, one of approach is improve the properity of PCB surface-treated metal layer or explore novel surface and process metal level, reduces process costs and improves rate of finished products.
Summary of the invention
In view of this, the invention provides a kind of PCB and surface treatment method thereof for encapsulation, improve PCB surface composition and treatment process with the reliability of raising PCB lead-free solder solder joint and reduce production costs.
A kind of PCB surface treatment method, comprise the following steps: a printed circuit board (PCB) is provided, this printed circuit board (PCB) comprises printed circuit board base board and is formed on copper pad on this printed circuit board base board, to the copper pad on described printed circuit board base board outer zone prevent the plating processing; The described copper pad of micro etch; Form a cobalt-based metal level on through the copper pad surface of micro etch, this cobalt-based metal level is used for directly contacting with lead-free solder; And it is also dry to clean the printed circuit board (PCB) that is formed with described cobalt-based metal level.
A kind of printed circuit board (PCB), it comprises that a printed circuit board base board and is arranged on the copper pad on this printed circuit board base board, wherein, further comprises a cobalt-based metal level, this cobalt-based metal level is set directly on copper pad, and is used for directly connecting lead-free solder and this copper pad.
With respect to prior art, the PCB of encapsulation use provided by the present invention and surface treatment method thereof have following effect: 1) the cobalt-based metal level bright appearance that obtains in the PCB surface treatment that reaches provided by the invention, and coating is even; And cobalt-based metal level wettability to lead-free solder when welding assembly is strong, and high with copper pad bond strength on substrate, simultaneously lead-free solder is had the effect that stops preferably Elements Diffusion, thereby improves the reliability of PCB lead-free solder solder joint; 2) the cobalt-based metal level in PCB provided by the invention directly connects lead-free solder and copper pad, has changed the composition of PCB surface-treated layer, makes the diffusion barrier effect increase, and makes Lead-Free Solder Joint be difficult for fatigue and creep occur, and has improved the reliability of long service.3) PCB surface treatment method provided by the invention as unique surface treatment mode, does not need to form other extra metal level with the cobalt metal level again, has reduced process procedure, reduces whole production cost.
Description of drawings
Fig. 1 is the surface treatment method flow chart that contains the cobalt metal level of PCB in the present invention.
Fig. 2 is the process flow for carrying out surface treatment figure that contains the cobalt metal level of the PCB that in the present invention, embodiment 1 and 2 provides.
Fig. 3 is the schematic diagram that in the present invention, in embodiment 3, the electroless cobalt plating layer on surface of metal of encapsulation IC installed surface substrate is processed.
Fig. 4 is contrast (cobalt-based metal level with the be untreated pcb board) figure of shear strength in test of pushing the ball in the embodiment of the present invention.
The main element symbol description
| The |
31 |
| |
32 |
| The |
33；42 |
| |
34；43 |
| |
35 |
| The |
36；44 |
| The cobalt-based |
37；45 |
| IC installed |
41 |
Following embodiment further illustrates the present invention in connection with above-mentioned accompanying drawing.
Embodiment
Below in conjunction with drawings and Examples, the PCB surface treatment method that the embodiment of the present invention is provided is described in detail.
See also Fig. 1, the invention provides a kind of PCB surface treatment method, it comprises the following steps:
S1 provides a printed circuit board (PCB) (PCB), and this PCB comprises the PCB substrate and be formed on copper (Cu) pad on this PCB substrate, to the Cu pad on described PCB substrate outer zone prevent the plating processing;
S2, the described Cu pad of micro etch;
S3 forms a cobalt-based metal level on the process Cu bond pad surface of micro etch, this cobalt-based metal level is used for directly contacting with lead-free solder, and wherein, this cobalt-based metal level is the metal level of cobalt metal simple-substance quality percentage composition maximum; And
S4 cleans the PCB and the drying that are formed with described cobalt-based metal level.
In step S1, described PCB substrate comprises rigidity PCB, flexible printed circuit (FPC), base plate for encapsulating semiconductor and TAB/COF band carrier.The electrode that zone, Cu pad other places on described PCB substrate is formed with wire and is connected with wire.Described Cu pad is the salient point that PCB is connected with other element or device, and is electrically connected to wire on PCB.Describedly the method that welding resistance and anti-plating process carried out in Cu pad on the PCB substrate outer zone specifically comprise the following steps:
S11 prevent that to the zone beyond the Cu pad on described PCB substrate the plating processing is affected avoiding in subsequent processes.Wherein, the zone beyond the Cu pad on this PCB substrate refers to the All Ranges except the zone that the Cu pad occupies on this PCB substrate, namely the non-Cu welding disking area on the PCB substrate.Particularly, the zone beyond Cu pad on the PCB substrate is formed a reserve or Continuous pressing device for stereo-pattern, be subject to the impact of subsequent processes to prevent the zone beyond the Cu pad on the PCB substrate.Wherein, this step S11 forms described reserve on the wire on the PCB substrate, and tapes on the electrode on the PCB substrate, in order to avoid the wire on the PCB substrate and electrode are subject to the impact of subsequent processing steps.The method that reserve in this step and the selection of adhesive tape and subsequent processing steps S2 and S3 realize and sample or the reagent of employing are relevant.The material of described reserve and adhesive tape can not affect normally carrying out of described step S2 and S3, preferably, and sample or reagent generation chemical reaction that the material of this reserve and adhesive tape can not adopt with described step S2 and S3.Before being appreciated that in this step S11, the zone beyond Cu pad on the PCB substrate prevents that plating is processed, can also carry out the step that welding resistance is processed to the zone beyond Cu pad on this PCB substrate.
S12; Adopt Ultrasonic Cleaning and dry the PCB that the anti-plating of described process is processed.
The main purpose of step S2 is in order to remove the impurity of the Cu bond pad surface in PCB, be conducive to form the cobalt-based metal level on the Cu pad.This step S2 comprises that further alligatoring goes deimpurity Cu bond pad surface.This step can adopt wet etching method or dry etching method to carry out micro etch to described PCB.Preferably, this step can adopt the dry etching method, realizes as plasma micro etch method.This step adopts the plasma etching method to carry out micro etch to the surface of Cu pad, when reducing Cu bond pad surface impurity, the surface of alligatoring Cu pad forms a plurality of micro-structurals in the Cu bond pad surface, increases the wettability of Cu pad, improves the bond strength with the prepared cobalt metal level of step S20.Particularly, will be placed in a plasma etching machine through the PCB that anti-plating is processed described Cu pad is carried out etching, this plasma etching machine comprises a vacuum pump.Wherein, the working gas of the plasma etching machine employing of this step employing is the mist of inert gas and oxygen.Oxygen in this working gas is mainly with the organic substances such as oil stain on the Cu pad that removes on the PCB substrate.Described inert gas mainly comprises helium, argon gas, neon, xenon or nitrogen.Preferably, this working gas is argon gas and air gas mixture.The flow of this plasma etching machine employing working gas can be under 5SCCM(standard state, every cubic centimetre per minute) ~ 20SCCM, power is 0.2 kilowatt of (KW) ~ 0.8KW.Air pressure in vacuum pump in this plasma etching machine is between 0.3 handkerchief (Pa) ~ 1 Pa.The time of using plasma etching machine etching processing preferably, can be chosen between min～10min more than or equal to 2 minutes (min), as 5min, and 8min etc., when being removed with the impurity that guarantees the Cu bond pad surface, the Cu bond pad surface is roughened.Be appreciated that in plasma micro etch process, the kind of the impurity in the Cu metal level in the inert gas in working gas and the ratio of oxygen and PCB is relevant.
In step S3, can adopt physics or chemical mode to form the cobalt-based metal level.Physics mode can be ion plating.Chemical mode can be the modes such as galvanoplastic or electroless plating method.The difference that the encapsulation that will satisfy according to prepared cobalt-based metal level requires can be selected different cobalt-based metal level preparation technologies.Preferably, this step S3 can adopt ultrasonic auxiliary galvanoplastic or ultrasound assisted chemical plating method to form described cobalt-based metal level on the process Cu pad of micro etch, namely, can first adopt galvanoplastic or ultrasound assisted chemical plating method to form the cobalt-based precipitated metal, simultaneously under the booster action that ultrasonic wave stirs, make the cobalt-based precipitated metal of formation be deposited on equably the surface of Cu pad.
When adopting ultrasonic auxiliary galvanoplastic to form described cobalt-based metal level, specifically comprise the following steps:
At first, an anode and described PCB substrate are placed in an electroplate liquid and are electrically connected to external power source in the interval simultaneously.Cu pad on described PCB substrate is as negative electrode.Described anode is the inert electrode sheets such as cobalt sheet, platinized platinum, palladium sheet, gold plaque.This electroplate liquid comprises a solubility cobalt salt and a reducing agent.Solubility cobalt salt in described electroplate liquid and reducing agent do not occur or the very difficult chemical reaction that occurs at normal temperatures.This solubility cobalt salt is in can being dissolved in water and forms the cobalt salt of cobalt ions, is used as oxidant, and cobalt ions is reduced into the cobalt metal simple-substance, as, cobaltous sulfate, cobalt chloride, cobalt carbonate, cobalt nitrate etc.The concentration of this solubility cobalt salt in electroplate liquid can be 0.1 mole every liter (mol/L) ~ 0.9 mol/L, as, 0.5 mol/L, 0.6, mol/L, 0.8 mol/L etc.This reducing agent refers to cobalt ions to be reduced to the medicament of cobalt metal simple-substance, as, phosphorous acid, phosphite, phosphorous acid monohydric salt, dihydrogen phosphite salt etc.This reducing agent is phosphorous acid, and preferably, the concentration of this reducing agent in electroplate liquid can be 0.01 mol/L ~ 0.5mol/L, as 0.2 mol/L, 0.4 mol/L etc.These galvanoplastic are mainly to carry out in the electroplate liquid of acidity, and the pH value of electroplate liquid maintains between 1～2.So this electroplate liquid also comprises an acid solution, this acid solution can be phosphoric acid, hydrochloric acid, dilute sulfuric acid etc.The concentration that is appreciated that this acid solution is not limit, and only has its pH value that can make electroplate liquid to get final product between maintaining 1～2.As, the concentration of this acid solution in electroplate liquid can be 0.01 mol/L ~ 0.6mol/L.
Secondly, apply voltage and this electroplate liquid of ultrasonic agitation between anode and described copper pad, make in the Cu pad electroplate liquid on every side on described PCB substrate and form the cobalt-based precipitated metal, and be deposited on the Cu pad.The current density that the voltage that applies between anode and described copper pad in this step produces is 1 A/dm
2~ 5A/dm
2, the temperature of electroplate liquid can be for 68 ℃ ~ 80 ℃, as 75 ℃.Described solubility cobalt salt forms cobalt ions in this electroplate liquid, when this electroplate liquid and described anode and described Cu pad formation conductive path, the anode that reducing agent attracted in electroplate liquid is neighbouring and oxidized, and cobalt ions is attracted near the Cu pad and is formed in addition the cobalt metal simple-substance.Under hyperacoustic stirring action, the cobalt-based precipitated metal is deposited on the surface of Cu pad equably.
Owing to may having the exert an influence pH value of whole electroplate liquid of acidic materials in electroplating process, thereby can affect electroplating effect, for this reason, this electroplate liquid can further include pH value conditioning agent, as carbonate, preferably, this carbonate is cobalt carbonate, and the concentration of cobalt carbonate in described electroplate liquid can be 0.05 mol/L ~ 0.15mol/L.When the pH of described electroplate liquid value hour, can by with carbonate reaction to improve the pH value.Can also add additive in this electroplate liquid, this additive can make the cobalt-based metal of formation more stable, and the final cobalt-based metal level that forms is brighter.This additive can be saccharin sodium, and the concentration of additive in described electroplate liquid can be 0 g/L ~ 0.12 g/L.In addition, when adopting the standby cobalt-based metal level of this ultrasonic auxiliary plating legal system, the temperature of electroplate liquid and the size of current density are selected according to the composition of electroplate liquid.
When adopting ultrasound assisted chemical plating method to form described cobalt-based metal level, this step specifically comprises the following steps:
At first, at normal temperatures that a solubility cobalt salt, a reducing agent and an alkaline solution is soluble in water, form a chemical plating fluid.The concentration of described solubility cobalt salt in this chemical plating fluid is 0.3 mol/L ~ 0.5mol/L.This chemical plating be the solubility cobalt salt that adopts can electroplate with reducing agent the time solubility cobalt salt and the reducing agent of employing identical.Solubility cobalt salt in this chemical plating fluid is also to be used as oxidant, and cobalt ions wherein is reduced into the cobalt metal simple-substance.Preferably, the reducing agent that adopts during this chemical plating is dihydrogen phosphite salt.The concentration of described reducing agent in this chemical plating fluid is 0.15 mol/L ~ 0.5mol/L.Described alkaline solution be the pH value of regulating this chemical plating fluid be 7.5 ~ 9.7, this alkaline solution is preferably ammoniacal liquor.
Secondly, adopt ultrasonic wave to stir this chemical plating fluid and make described solubility cobalt salt and reducing agent generation redox reaction to form described cobalt-based metal level.Particularly, described solubility cobalt salt and reducing agent are usually lower at alkaline environment and redox reaction occurs at a certain temperature form the cobalt metal simple-substance.Under hyperacoustic stirring action, cobalt simple substance precipitation is dispersed in chemical plating fluid and is deposited on equably the surface of Cu pad.Be appreciated that in the chemical plating process, the pH value of chemical plating fluid and temperature are relevant with selected solubility cobalt salt and reducing agent, are also the necessary conditions that promotes that solubility cobalt salt and reducing agent react.As, work as CoSO
47H
2O adopts NaH as the solubility cobalt salt
2PO
2During for reducing agent, the scope of pH value is 7.5 ~ 9.7, and the temperature of chemical plating fluid is 80 ℃ ~ 95 ℃.
In addition, be formed on better on the Cu pad in order to make the cobalt-based metal, can also add complexing agent in this chemical plating fluid.This complexing agent can with the complexing of cobalt simple substance, play the effect of stablizing cobalt simple substance, thereby make the cobalt-based metal level of final formation dense, bright.This complexing agent can be sodium potassium tartrate tetrahydrate (C
4O
6H
4KNa) or trisodium citrate (Na
3C
6H
5O
76H
2O) etc. can with the complex compound of cobalt simple substance complexing.The concentration of this complexing agent in described chemical plating fluid can be 0 ~ 0.25mol/L.
The cobalt-based metal level that this step S3 forms is formed directly into the surface of Cu pad, and is used for directly connecting Cu pad and lead-free solder.The quality percentage composition of the cobalt element in this cobalt-based metal level is between 60% ~ 98%.Bond strength between cobalt-based metal level and PCB substrate Cu pad is between 45 milli newton (mN) ~ 100mN.The thickness of described cobalt metal level is 2 microns (μ m) ~ 8 μ m, and it can be electroplated or the chemical plating plating time decides by control.Select according to PCB encapsulated type and product requirement, select the time of plated film.
The composition of the cobalt-based metal level that this step S3 forms is relevant with the composition of the electroplate liquid that adopts or chemical plating fluid.The pH value of electroplate liquid maintains between 1～2, and the concentration of solubility cobalt salt wherein is between 0.1mol/L ~ 0.9 mol/L, concentration 0.01 mol/L of reducing agent ~ 0.5mol/L, simultaneously under the cooperation of the conditions such as temperature and operating current, can keep the reaction of solubility cobalt salt and reducing agent composition to form described cobalt-based metal level, make this cobalt-based metal level directly contact lead-free solder and copper pad, need not additionally to increase other metal level.This lead-free solder comprises solder ball, and the composition of this solder ball mainly comprises the metals such as tin, silver, copper.In addition, the pH value of chemical plating fluid maintains between 7.5 ~ 9.7, and the concentration of solubility cobalt salt wherein is between 0.3 mol/L ~ 0.5mol/L, concentration 0.15 mol/L of reducing agent ~ 0.5mol/L, under the cooperation of the conditions such as temperature, the cobalt-based metal level of formation also can directly connect lead-free solder and copper pad simultaneously.
No matter adopt above-mentioned galvanoplastic or electroless plating method, the cobalt-based metal level that this step S3 forms is especially tin, silver and copper with main component Pb-free solder ball has reasonable wettability, and bond strength is higher.So, when adopting this Pb-free solder ball welding, can improve reliability and stability between lead-free solder and Cu pad.
Step S4 comprises step by step following: S41, water clean the described pcb board that is formed with the cobalt-based metal level to remove the material that remains in step S3 on the cobalt-based metal level, as chemical plating fluid, electroplate liquid, and dry; And S42, remove reserve or Continuous pressing device for stereo-pattern on the pcb board that is formed with the cobalt-based metal level after water cleans, coordinate ultrasonic vibration to clean, and dry.Wherein, according to the difference of the reserve that adopts in step S10, the method for removing reserve is also different.Usually, reserve can adopt strong alkali solution to remove.Reserve is that to adopt concentration be that the sodium hydroxide solution of 0.01 mol/L ~ 0.04mol/L is removed by the spray mode, and solution temperature is 25 ℃ ~ 40 ℃.
The surface treatment method of PCB provided by the invention has the following advantages: the PCB surface of adopting 1) that said method processes can form the cobalt-based metal level, the bright appearance of this cobalt-based metal level, coating is even, and cobalt-based metal level wettability to lead-free solder when welding assembly is strong, and with copper pad on substrate, high bond strength is arranged, thereby improve the reliability of PCB lead-free solder solder joint.2) the present invention as unique surface treatment mode, does not need to form other extra metal level with the cobalt metal level again, has reduced process procedure, reduces whole production cost.3) therefore, cobalt-based metal level in PCB provided by the invention directly connects lead-free solder and copper pad, changed the composition that the PCB surface treatment method has changed the PCB surface-treated layer, the cobalt-based metal level has the reasonable diffusion that stops to lead-free solder, and the decay resistance with good high-temperature oxidation resistance and excellence, can make Lead-Free Solder Joint be difficult for fatigue and creep occur, improve the reliability of long service.
Further set forth the present invention below in conjunction with embodiment particularly.
Embodiment 1
See also Fig. 2, a kind of PCB surface treatment method for semiconductor packages comprises the following steps:
(1) with the zone that needs on PCB substrate 31 beyond the circular Cu pad 36 of surface-treated, comprise on output lead 35 that coating solder resist and oven dry form a welding resistance zone 33, having regional 33 surface uniforms of welding resistance to apply the anti-plated films 34 of one decks, wire is inputted/is gone out the rear outer peripheral areas with not needing to electroplate of end connection and covers with adhesive tape 32; Be formed with PCB substrate 31 and the drying of above-mentioned reserve/adhesive tape with Ultrasonic Cleaning, wherein, the diameter of this Cu pad 36 is 0.5 millimeter;
(2) PCB after cleaning puts into plasma cleaning equipment and carries out micro etch 3min, and working gas is argon gas and air gas mixture, and the flow of this working gas is 10SCCM, and power is 0.2KW, by vacuum pump holding chamber internal gas pressure at 0.9 Pa;
(3) adopt galvanoplastic to form cobalt-based metal level 37 on the PCB surface, particularly, electroplating the anode that adopts is the cobalt sheet, and negative electrode is the surface mount pad on pcb board, and electroplate liquid consists of the CoCl that concentration is 0.15mol/L
26H
2O, concentration is the CoCO of 0.06mol/L
3, concentration is the H of 0.015mol/L
3PO
4, concentration is the H of 0.015mol/L
3PO
3, temperature is 70 ℃, current density is 1.2A/dm
2, plated film times 2 min applies ultrasonic assistant depositing;
(4) the PCB plate after effects on surface is processed carries out clear water and rinses, and dry;
(5) sodium hydroxide solution that is 0.02mol/L with concentration is removed anti-plated film 34 by the spray mode, and solution temperature is 30 ℃.Remove the adhesive tape of communication conductive wire surface binded after rinsing through water, coordinate ultrasonic vibration water to clean, and dry;
(6) be that the Sn-3.5Ag-0.5Cu solder ball of 0.6 millimeter is planted in the PCB surface with diameter, chip is fixed on the tin ball by the reflow soldering welding assembly with positioning fixture.
The content of the Co element of PCB surface preparation cobalt-based metal level 37 is 95.2%, and thickness is 3.5 μ m.As shown in Figure 4, when the speed that adopts 500 little meter per seconds was moved back above-mentioned solder ball, the shear strength of pushing the ball after encapsulation was 15.5N.In addition, under identical condition, the PCB that does not process through said method, the shear strength of pushing the ball after encapsulation is 9.2N.Wherein, " being untreated " in Fig. 4 refers to the PCB that does not process through above-mentioned surface treatment method.Therefore, the PCB that obtains after the disposal methods that is provided by embodiment 1 when encapsulation wherein cobalt-based metal level 37 and solder ball between wettability is preferably arranged, higher bond strength, thus improve the reliability of PCB lead-free solder solder joint.
Embodiment 2
See also Fig. 2, a kind of PCB surface treatment method for semiconductor packages comprises the following steps:
(1) with embodiment 1;
(2) with embodiment 1, wherein, the micro etch processing time is 4min, and the flow of working gas is 9SCCM, and power is 0.3KW, by vacuum pump holding chamber internal gas pressure at 0.8 Pa;
(3) adopt to electroplate on the PCB surface and form cobalt-based metal level 37, electroplating the anode that adopts is the cobalt sheet, and negative electrode is the circular Cu pad on pcb board, and electroplate liquid consists of the CoCl that concentration is 0.15mol/L
26H
2O, concentration is the CoCO of 0.095mol/L
3, concentration is the H of 0.35mol/L
3PO
4, concentration is the H of 0.15mol/L
3PO
3, concentration is the saccharin sodium of 0.02 g/L, and temperature is 75 ℃, and current density is 3.5A/dm
2, the plated film time is 8min, applies ultrasonic assistant depositing;
(4) with embodiment 1;
(5) sodium hydroxide solution that is 0.04mol/L with concentration is removed anti-plated film 34 by the spray mode, and solution temperature is 55 ℃.Remove the adhesive tape 32 of communication conductive wire surface binded after rinsing through water, coordinate ultrasonic vibration water to clean, and dry;
(6) with embodiment 1;
The content of the Co element of band structure PCB surface preparation cobalt-based metal level 37 is 85.5%, and thickness is 5.8 μ m.As shown in Figure 4, when the speed that adopts 500 little meter per seconds was moved back above-mentioned solder ball, the shear strength of pushing the ball after encapsulation was 12.4N, and this shear strength of pushing the ball is greater than the be untreated shear strength of pushing the ball after rear encapsulation of PCB under the same conditions.So, the PCB that obtains after the disposal methods that adopts embodiment 2 to provide when encapsulation wherein cobalt-based metal level 37 and solder ball between wettability is preferably arranged, higher bond strength, thus improve the reliability of PCB lead-free solder solder joint.
Embodiment 3
A kind of surface treatment method of the IC installed surface substrate for encapsulating obtains the encapsulation IC installed surface substrate that contains the cobalt-based metal level that is formed with as shown in Figure 3.This surface treatment method comprises the following steps:
(1) will need zone coating solder resist beyond surface treatment surface mount Cu pad 44 and oven dry to form a welding resistance zone 42 on IC installed surface substrate 41, there are being regional 42 surface uniforms of welding resistance to apply the anti-plated films 43 of one decks, clean and drying with ultrasonic wave water at last, wherein, the diameter of this Cu pad 36 is 0.5 millimeter;
(2) PCB after cleaning puts into plasma cleaning equipment and carries out micro etch 8min, and working gas is argon gas and air gas mixture, and flow is 5SCCM, and power is 0.4KW, by vacuum pump holding chamber internal gas pressure at 1 Pa;
(3) with IC installed surface substrate with after Pd activation, adopt the ultrasound assisted chemical plating to form in its surface cobalt-based metal level 45, this cobalt-based metal level 45 is the Co-P film; Particularly, the plating solution of this chemical plating consists of the CoSO that concentration is 0.35mol/L
47H
2O, concentration is the NaH of 0.18mol/L
2PO
2, concentration is the C of 0.12mol/L
4O
6H
4KNa, it is 9.0 that ammoniacal liquor is regulated the pH value, and temperature is 90 ℃, and the plated film time is 5min;
(4) the PCB plate after effects on surface is processed carries out clear water and rinses, and dry;
(5) sodium hydroxide solution that is 0.04mol/L with concentration is removed anti-plated film by the spray mode, and solution temperature is 58 ℃.Coordinate ultrasonic vibration water to clean, and dry;
(6) adopt the Sn-3.5Ag-0.5Cu solder ball to plant in IC installed surface substrate, weld encapsulation by reflow soldering.
The content of the Co element of IC installed surface substrate 41 surface preparation Co-P films is 96.7%, and thickness is 2 μ m.As shown in Figure 4, when the speed that adopts 500 little meter per seconds was moved back above-mentioned solder ball, the shear strength of pushing the ball after encapsulation was 9.9N, and this shear strength of pushing the ball is greater than the be untreated shear strength of pushing the ball after rear encapsulation of PCB under the same conditions.So, the PCB that obtains after the disposal methods that adopts embodiment 3 to provide when encapsulation wherein the Co-P film and solder ball between wettability is preferably arranged, higher bond strength, thus improve the reliability of PCB lead-free solder solder joint.
In addition, those skilled in the art also can do other variations in spirit of the present invention, and certainly, the variation that these are done according to spirit of the present invention is within all should being included in the present invention's scope required for protection.
Claims (15)
1. printed circuit board surface processing method comprises the following steps:
One printed circuit board (PCB) is provided, and this printed circuit board (PCB) comprises printed circuit board base board and is formed on copper pad on this printed circuit board base board, to the copper pad on described printed circuit board base board outer zone prevent the plating processing;
The described copper pad of micro etch;
Form a cobalt-based metal level on through the copper pad surface of micro etch, this cobalt-based metal level is used for directly contacting with lead-free solder; And
Cleaning is formed with printed circuit board (PCB) and the drying of described cobalt-based metal level.
2. printed circuit board surface processing method as claimed in claim 1, is characterized in that, the method for the described copper pad of micro etch is for adopting impurity and this copper pad of alligatoring on the described copper pad of plasma etching method removal.
3. printed circuit board surface processing method as claimed in claim 2, it is characterized in that, impurity on the described copper pad of described employing plasma etching method removal and the step of this copper pad of alligatoring are: will be placed in a plasma etching machine through the printed circuit board (PCB) that anti-plating is processed described copper pad is carried out etching, this plasma etching machine comprises a vacuum pump, air pressure in this vacuum pump is 0.3 handkerchief ~ 1 handkerchief, the working gas that this plasma etching machine adopts is the mist of oxygen and inert gas, the flow of the working gas that this plasma etching machine adopts is 5 SCCM ~ 20SCCM, the power that this plasma etching machine adopts is 0.2 kilowatt ~ 0.8 kilowatt, and the operating time of this plasma etching machine was more than or equal to 2 minutes.
4. printed circuit board surface processing method as claimed in claim 1, is characterized in that, the method for described formation cobalt-based metal level is ultrasonic auxiliary galvanoplastic or ultrasound assisted chemical plating method.
5. printed circuit board surface processing method as claimed in claim 4, it is characterized in that, the method that adopts ultrasonic auxiliary galvanoplastic to form described cobalt-based metal level comprises: the substrate of an anode and described printed circuit board (PCB) is placed in an electroplate liquid in the interval simultaneously, this electroplate liquid comprises a solubility cobalt salt, one reducing agent and an acid solution, the concentration of this solubility cobalt salt in this electroplate liquid is between 0.1 mole every liter ~ 0.9 mole every liter, the concentration of this reducing agent in this electroplate liquid is between 0.01 mole every liter ~ 0.5 mole every liter, the pH value of this electroplate liquid is between 1～2, and apply voltage and this electroplate liquid of ultrasonic agitation between anode and described copper pad, make in the electroplate liquid around the copper pad on the substrate of described printed circuit board (PCB) and form the cobalt-based precipitated metal, and be deposited on copper pad.
6. printed circuit board surface processing method as claimed in claim 5, is characterized in that, described reducing agent is phosphorous acid, phosphite, phosphorous acid monohydric salt or dihydrogen phosphite salt.
7. printed circuit board surface processing method as claimed in claim 5, is characterized in that, described electroplate liquid further comprises pH value conditioning agent, and this pH value conditioning agent is carbonate.
8. printed circuit board surface processing method as claimed in claim 5, it is characterized in that, described electroplate liquid comprises cobalt chloride, cobalt carbonate, phosphoric acid, phosphorous acid and saccharin sodium, the temperature of this electroplate liquid is 68 ℃ ~ 80 ℃, and the current density that the voltage that applies between anode and described copper pad produces is 1 A/dm
2~ 5A/dm
2
9. printed circuit board surface processing method as claimed in claim 4, it is characterized in that, the method that adopts ultrasound assisted chemical plating method to form described cobalt-based metal level comprises: at normal temperatures, one solubility cobalt salt, a reducing agent and an alkaline solution is soluble in water, form a chemical plating fluid, and the concentration of this solubility cobalt salt in this electroplate liquid is between 0.3 mole every liter ~ 0.5 mole every liter, the concentration of this reducing agent in this electroplate liquid is between 0.01 mole every liter ~ 0.5 mole every liter, and the pH value of this electroplate liquid is between 7.5 ~ 9.7; And be between 80 ℃ ~ 95 ℃ the time in the temperature of chemical plating fluid, adopt ultrasonic wave to stir this chemical plating fluid and make described solubility cobalt salt with reducing agent generation redox reaction with the described cobalt-based metal level of formation on described copper pad.
10. printed circuit board surface processing method as claimed in claim 9, is characterized in that, described chemical plating fluid further comprises complexing agent, and this complexing agent is sodium potassium tartrate tetrahydrate or trisodium citrate.
11. printed circuit board surface processing method as claimed in claim 10 is characterized in that, the solubility cobalt salt in described chemical plating fluid is that cobaltous sulfate, described reducing agent are NaH
2PO
2, described alkaline solution is ammoniacal liquor.
12. printed circuit board (PCB), it comprises that a printed circuit board base board and is arranged on the copper pad on this printed circuit board base board, it is characterized in that, further comprise a cobalt-based metal level, this cobalt-based metal level directly arranges and covers on copper pad, and is used for directly connecting lead-free solder and this copper pad.
13. printed circuit board (PCB) as claimed in claim 12 is characterized in that, the content of the cobalt element in described cobalt-based metal level is between 60% ~ 98%.
14. require 12 described printed circuit board (PCB)s as profit, it is characterized in that, the bond strength between described cobalt-based metal level and described copper pad is between 45 milli newton ~ 100 milli newton.
15. require 12 described printed circuit board (PCB)s as profit, it is characterized in that, the thickness of described cobalt-based metal level is 2 microns ~ 8 microns.
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| CN107124829A (en) * | 2016-02-25 | 2017-09-01 | 东莞新科技术研究开发有限公司 | Pcb surface processing method |
| CN107119280A (en) * | 2016-02-25 | 2017-09-01 | 东莞新科技术研究开发有限公司 | Bond pad surface processing method |
| CN107119298A (en) * | 2016-02-25 | 2017-09-01 | 东莞新科技术研究开发有限公司 | Pcb surface processing method |
| CN110132960A (en) * | 2018-02-09 | 2019-08-16 | 环鸿电子（昆山）有限公司 | The detection method of circuit board assemblies |
| CN110708881A (en) * | 2019-11-13 | 2020-01-17 | 重庆秦嵩科技有限公司 | PCB surface treatment method |
| CN113950197A (en) * | 2021-09-07 | 2022-01-18 | 德中（天津）技术发展股份有限公司 | Circuit board manufacturing method for conducting on-off inspection in bare board manufacturing stage |
| CN114171661A (en) * | 2020-09-10 | 2022-03-11 | 京东方科技集团股份有限公司 | Light-emitting substrate, display device and manufacturing method |
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Application publication date: 20131106 |