JP2011167753A - Solder paste, substrate for pin grid array package using the same, and pin grid array package, and method for manufacturing substrate for pin grid array package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solder paste containing lead-free solder powder and flux, and capable of dropping the reflow temperature when soldering a terminal to a conductive connection pin, and enhancing the pin erection property after mounting package components, a substrate for a pin grid array package and the pin grid array package using the same, and a method for manufacturing the substrate for the pin grid array package. <P>SOLUTION: The solder paste (4) for the pin grid array package contains Sn/Sb base lead-free solder powder, and flux. The Sn/Sb base lead-free solder powder contains first solder powder, and second solder powder having the melting point higher than that of the first solder powder. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solder paste used when bonding terminals and conductive connection pins in a manufacturing process of a pin grid array package, a pin grid array package substrate and a pin grid array package using the same, and a pin grid array The present invention relates to a method for manufacturing a package substrate.

  As a conventional method for manufacturing a pin grid array package (hereinafter also referred to as a PGA package), for example, a method described in Patent Document 1 can be cited. 4A to 4E are cross-sectional views for each process of the method for manufacturing a PGA package described in Patent Document 1. FIG. First, the base material 1 in which the terminal 2 is formed on one side is prepared (FIG. 4A). Next, a solder paste 30 containing Sn / Pb solder having a low melting point is printed on the surface of the substrate 1 opposite to the surface on which the terminals 2 are formed (FIG. 4B). Next, a solder paste 40 containing a high melting point Sn / Pb solder is printed on the terminal 2 (FIG. 4C). Next, by reflowing the conductive connection pin 5 in contact with the solder paste 40, as shown in FIG. 4D, the terminal 2 and the conductive connection pin 5 are Sn / Pb-based in the solder paste 40. It joins by the electroconductive connection part 60 which consists of solder. At the same time, the solder bumps 70 are formed by the Sn / Pb solder in the solder paste 30. Next, the package component 8 is placed on the solder bump 70 and reflowed to obtain the PGA package shown in FIG. 4E.

  However, in recent years, regulations on lead have been strengthened due to the problem of environmental pollution, and switching from Sn / Pb solder powder to lead-free solder powder is being made.

  However, a lead-free solder represented by a 99.3 Sn / 0.7 Cu alloy (mass ratio is Sn / Cu = 99.3 / 0.7) has a melting point that is about 40 ° C. higher than that of Sn / Pb solder. Therefore, a high temperature of about 230 ° C. is required as the reflow temperature when mounting the package components. Therefore, as shown in FIG. 5, the conductive connection pin 5 is tilted or falls due to the reflow process for mounting the package component 8, and the perpendicularity of the conductive connection pin 5 with respect to the base material 1 (pin stand) It has been found by the study of the present inventors that there is a possibility that the property may be reduced.

JP 2001-223290 A

  On the other hand, if a high melting point solder is used as the solder for joining the terminal and the conductive connection pin, the deterioration of the pinning property can be suppressed. However, in recent years, PGA packages have been shifting from conventional ceramic bases to resin bases in order to reduce the thickness and weight of electronic devices. Due to the reflow process for bonding the conductive connection pins, the resin base material may be deteriorated, and the reliability of the PGA package substrate may be impaired.

  Therefore, the solder paste used when joining the terminal and the conductive connection pin is excellent in pin standability and reflow when joining the terminal and the conductive connection pin to prevent deterioration of the resin-based substrate. What can lower the temperature is desired. In the conventional solder paste, the above problems have not been sufficiently studied.

  In the solder paste containing lead-free solder powder and flux, the present invention can lower the reflow temperature when joining the terminal and the conductive connection pin, and can improve the pinning property after mounting the package component. A solder paste, a pin grid array package substrate using the solder paste, a pin grid array package, and a method of manufacturing the pin grid array package substrate are provided.

  By using two types of Sn / Sb lead-free solder powders having different melting points, the present inventors can lower the reflow temperature when joining the terminal and the conductive connection pin, and mount the package component. As a result, the inventors have found that the pinning property after the improvement can be improved, and have completed the present invention.

  That is, the solder paste of the present invention is a solder paste for a pin grid array package, and contains Sn / Sb-based lead-free solder powder and flux, and the Sn / Sb-based lead-free solder powder is first And a second solder powder having a melting point higher than that of the first solder powder.

  The pin grid array package substrate of the present invention is a pin grid array package substrate having a base, terminals disposed on one side of the base, and conductive connection pins disposed on the terminals. The terminal and the conductive connection pin are joined using the solder paste of the present invention.

  The pin grid array package of the present invention is mounted on the surface opposite to the surface on which the pin grid array package substrate of the present invention and the conductive connection pins of the pin grid array package substrate are disposed. And a package component.

  A method for manufacturing a substrate for a pin grid array package according to the present invention is for a pin grid array package having a base material, terminals arranged on one side of the base material, and conductive connection pins arranged on the terminals. A method for manufacturing a substrate, wherein the terminal and the conductive connection pin are joined using the solder paste of the present invention.

  According to the solder paste of the present invention, it is possible to provide a solder paste capable of lowering the reflow temperature when joining the terminal and the conductive connection pin, and improving the pin standability after mounting the package component. Further, according to the pin grid array package substrate, the manufacturing method thereof, and the pin grid array package of the present invention, it is possible to provide a pin grid array package that suppresses deterioration of the substrate due to the reflow process and has excellent pinning property. it can.

AE is sectional drawing according to process which shows an example of the manufacturing method of the PGA package of this invention. 6 is a graph showing reflow conditions for condition A. 6 is a graph showing a reflow condition of condition B. AE is sectional drawing according to process which shows an example of the manufacturing method of the conventional PGA package. It is sectional drawing which shows an example of the conventional PGA package.

  The solder paste of the present invention is a solder paste used when joining terminals and conductive connection pins in a PGA package manufacturing process, and is intended for a solder paste containing lead-free solder powder and flux. As the lead-free solder powder, Sn / Sb-based lead-free solder powder containing a first solder powder and a second solder powder having a melting point higher than that of the first solder powder is used. In the present invention, the “melting point” refers to the melting start temperature and refers to the solidus temperature in differential scanning calorimetry (DSC). Hereinafter, the components contained in (or can be contained in) the solder paste of the present invention will be described.

(Sn / Sb lead-free solder powder)
In the present invention, Sn / Sb-based lead-free solder powder is used, and “lead-free solder powder” refers to solder powder to which lead is not added. However, the presence of lead as an inevitable impurity in the solder powder is allowed, but in this case, the amount of lead is preferably 1000 ppm or less.

  The Sn / Sb lead-free solder powder used in the present invention contains a first solder powder and a second solder powder having a melting point higher than that of the first solder powder. When two types of solder powders having different melting points are used, the first solder powder (low melting point solder) is first melted in the reflow process when joining the terminal and the conductive connection pin, and this molten low melting point solder is used. Is in contact with the second solder powder having a high melting point, and these are fused, so that the entire solder is easily melted and the reflow temperature can be lowered. Thereby, for example, the reflow temperature can be lowered to less than 250 ° C. Further, the second solder powder having a high melting point is fused through the first solder powder, whereby the solder joint portion is strengthened, and both the first and second solder powders are Sn / Sb-based. Since it is a solder powder, it is considered that pin standability is improved.

  As the first solder powder, for example, a solder powder having a melting point of preferably less than 230 to 240 ° C., more preferably 232 to 238 ° C. can be used. As the second solder powder, for example, a solder powder having a melting point of preferably less than 240 to 260 ° C., more preferably 240 to 250 ° C. can be used. From the viewpoint of reducing the reflow temperature and improving the pinning property, the difference in melting point between the first solder powder and the second solder powder is preferably 5 to 30 ° C, more preferably 10 to 25 ° C. Examples of a method for controlling the melting point of the solder powder include a method for adjusting the content ratio of Sn and Sb. That is, increasing the Sb content ratio increases the melting point, and decreasing the Sb content ratio decreases the melting point.

  As a specific example of the first solder powder, from the viewpoint of reducing the reflow temperature, a solder powder consisting of 3 to 7% by mass of Sb and the remaining Sn is preferable, and a solder powder consisting of 3 to 6% by mass of Sb and the remaining Sn is more preferable. In addition, as a specific example of the second solder powder, from the viewpoint of improving pin standability, a solder powder composed of Sb 10 to 20% by mass and the remaining Sn is preferable, and from the viewpoint of achieving both reflow temperature reduction and pin stand improvement. A solder powder composed of 10 to 18% by mass of Sb and the remaining Sn is more preferable. Note that the “remainder Sn” does not mean that all components other than Sb are strictly composed of Sn, and it is allowed that components other than Sb and Sn exist as unavoidable impurities. Is done. In this case, the amount of the other component is preferably 1000 ppm or less from the viewpoint of reducing the reflow temperature and improving the pinning property. The content of Sn is preferably 80 to 97% by mass, more preferably 82 to 97% by mass, and 84 to 97% by mass from the viewpoint of improving the reliability of the joint portion between the terminal and the conductive connection pin. % Is more preferable.

  The content of the first solder powder in the Sn / Sb-based lead-free solder powder is preferably 10 to 40% by mass from the viewpoint of reducing the reflow temperature and improving the pinning property, and is 15 to 35% by mass. More preferably, it is more preferably 20 to 30% by mass.

  The content of the second solder powder in the Sn / Sb-based lead-free solder powder is preferably 60 to 90% by mass, and 65 to 85% by mass from the viewpoint of reducing the reflow temperature and improving the pinning property. More preferably, it is more preferably 70 to 80% by mass.

  The Sn / Sb-based lead-free solder powder used in the present invention preferably has an average particle size of 1 to 50 μm, more preferably 5 to 45 μm, and still more preferably 10 to 40 μm. By setting the average particle size to 1 μm or more, the solder paste can be easily adjusted to a viscosity suitable for printing. On the other hand, when the average particle size is 50 μm or less, it is possible to easily cope with a narrow pitch of the pin interval of the PGA package. The “average particle diameter” can be measured with a laser diffraction analyzer. As the laser diffraction type analyzer, for example, a laser diffraction particle analyzer Coulter LS130 (manufactured by BECMAN COULTER) can be used.

  The Sn / Sb-based lead-free solder powder used in the present invention may further contain another Sn / Sb-based solder powder in addition to the first and second solder powders. For example, a third solder powder having a melting point intermediate between the first solder powder and the second solder powder may be included.

(flux)
The flux used by this invention is not specifically limited, The thing of the mixing | blending used with the conventional solder paste can be used. For example, a rosin resin-containing flux, a thermosetting resin-containing flux, or the like can be used. Especially, it is preferable to use a rosin-based resin-containing flux from the viewpoint of workability during soldering and ease of repair.

  As the rosin resin-containing flux, a flux containing a rosin resin, an activator, a thixotropic agent, a solvent and the like can be used. Examples of the rosin-based resin include rosin and derivatives thereof such as modified rosin, and these can be used in combination. Specific examples include gum rosin, wood rosin, polymerized rosin, phenol-modified rosin, and derivatives thereof. The content of the rosin resin is preferably 30 to 70% by mass in the flux from the viewpoint of solderability. Activators include organic amine hydrohalides and organic acids, specifically diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine hydrochloride, triethanolamine hydrobromide. Salts, monoethanolamine hydrobromide, adipic acid, sebacic acid and the like. The content of the activator is preferably 0.1 to 10% by mass in the flux from the viewpoint of suppressing corrosion due to the residue and not impairing the insulation resistance, and further from the viewpoint of preventing solderability and solder balls. . Examples of the thixotropic agent include hydrogenated castor oil, hydrogenated castor oil, fatty acid amides, and oxy fatty acids. The content of the thixotropic agent is preferably 3 to 15% by mass in the flux from the viewpoint of adjusting the solder paste to a viscosity suitable for printing. Examples of the solvent include hexyl carbitol, hexyl diglycol, butyl carbitol and the like. The content of the solvent is preferably 30 to 50% by mass in the flux from the viewpoint of adjusting the solder paste to a viscosity suitable for printing.

  In the solder paste of the present invention, the flux content is preferably 9 to 13% by mass, and more preferably 10 to 12% by mass. By setting it as the said range, the viscosity and thixotropy as a paste will become favorable, and the solder paste suitable for mass production processes, such as printing and dispensing application | coating, will be obtained. From the same viewpoint, in the solder paste of the present invention, the content of the Sn / Sb-based lead-free solder powder is preferably 81 to 91% by mass, and more preferably 88 to 90% by mass.

  The solder paste of the present invention or the flux contained in the solder paste contains various additives as necessary, for example, additives such as surfactants, antifoaming agents, leveling agents, etc. in addition to the above-described components. be able to. Among these, it is preferable to add a surfactant because solder wettability is improved.

  The solder paste of the present invention can be easily produced by kneading together with the above-described essential components and additives added as necessary.

  Next, a method for manufacturing a PGA package substrate using the solder paste of the present invention and a method for manufacturing a PGA package will be described with reference to FIGS.

  First, as shown in FIG. 1A, a base material 1 having terminals 2 formed on one side is prepared. The substrate 1 is not particularly limited, and a single-layer or multilayer ceramic-based substrate, a single-layer or multilayer resin-based substrate, or the like can be used, but the resin-based substrate is used at a high temperature (particularly 250 ° C. or higher). When a reflow process described later is performed, discoloration, deformation, and the like are likely to occur. Therefore, when using a resin-based substrate, it is desirable to employ a reflow temperature of less than 250 ° C. According to the present invention, since the reflow temperature can be easily reduced, the effect of the present invention is particularly effectively exhibited when a resin-based substrate is used as the substrate 1.

  Next, as shown in FIG. 1B, a solder paste 3 is applied to the surface of the substrate 1 opposite to the surface on which the terminals 2 are formed. The coating method is not particularly limited, and a screen printing method, a dispense coating method, or the like can be employed.

  The solder paste 3 is not particularly limited as long as a solder powder having a melting point lower than that of a solder powder in the solder paste 4 described later is included, but a solder paste containing a lead-free solder powder is preferable from the viewpoint of reducing environmental burden. . Examples of the lead-free solder powder include Sn / Cu series, Sn / Bi series, Sn / In series, Sn / Zn series, Sn / Ag / Cu series, and Sn / Cu / Bi series. From the viewpoint of cost, it is preferable to use a solder paste containing Sn / Cu-based lead-free solder powder as the solder paste 3.

  Next, as shown in FIG. 1C, the above-described solder paste 4 of the present invention is applied onto the terminals 2. The coating method is not particularly limited, and a screen printing method, a dispense coating method, or the like can be employed.

  Next, by reflowing the conductive connection pin 5 in contact with the solder paste 4, as shown in FIG. 1D, the terminal 2 and the conductive connection pin 5 are Sn / Sb-based in the solder paste 4. It joins by the electroconductive connection part 6 which consists of solder. At the same time, solder bumps 7 are formed by solder (preferably Sn / Cu lead-free solder) in the solder paste 3. In this case, the reflow temperature is preferably less than 250 ° C. from the viewpoint of preventing discoloration and deformation of the substrate 1. Through the above steps, the PGA package substrate 10 shown in FIG. 1D is obtained.

  Further, as shown in FIG. 1E, a PGA package 20 is obtained by placing a package component 8 such as an IC or LSI on the solder bump 7 of the PGA package substrate 10 obtained as described above and performing reflow. . The reflow temperature at this time is usually 230 ° C. or higher when a solder paste containing lead-free solder powder is used as the solder paste 3. Thus, even if the reflow process for mounting the package component 8 at a high temperature is performed, the PGA package 20 with good pinning property can be obtained by using the above-described solder paste of the present invention as the solder paste 4. .

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above embodiment, the solder paste of the present invention (pin fixing solder paste) is applied after the package component mounting solder paste is applied, but the order of application may be reversed.

  Moreover, in the said embodiment, although the solder bump was formed in the board | substrate for PGA packages, the solder bump does not need to be formed in the board | substrate for PGA packages of this invention. In that case, for example, a solder bump may be provided on the package component side, and the package component may be mounted by joining the solder bump and a terminal on the PGA package substrate.

  Hereinafter, the present invention will be described in more detail with reference to examples. These examples are examples of the best mode of the present invention, but the present invention is not limited by these examples.

(Preparation of solder paste for pin fixing)
Rosin resin (Harima Chemical Co., Ltd. Hariphenol 512) 48% by mass, thixotropic agent (cured castor oil) 9% by mass, activator (adipic acid) 8% by mass, surfactant (BYK361N, BYK361 Japan) 1 Mass% and 34% by mass of hexyl diglycol as a solvent were weighed in the same container and mixed using a rough machine to prepare a flux. The obtained flux and the pin fixing solder powder shown in Table 1 were weighed in a ratio of flux: solder powder = 10: 90, and these were mixed in a kneader for 2 hours to obtain a pin fixing solder paste. Was prepared. In Table 1, the melting points of the solder powders A and B were measured using a differential scanning calorimeter (DSC6200, manufactured by Seiko Instruments Inc.) under a nitrogen atmosphere at a heating rate of 10 ° C./min and a measurement temperature range. It measured as 30-600 degreeC. At the time of measurement, those having an endotherm of 1.5 J / g or more were regarded as peaks derived from the measurement object, and peaks less than that were excluded from the viewpoint of analysis accuracy.

(Preparation of solder paste for mounting package parts)
In the method for preparing the solder paste for pin fixing, the package was prepared in the same manner as above except that 99.3 Sn / 0.7 Cu alloy solder powder (melting point by the above measuring method: 227 ° C.) was used as the lead-free solder powder A solder paste for component mounting was prepared.

(Evaluation of pinning ability)
What is the land surface of a glass epoxy substrate (FR-4, thickness 0.6 mm (conductor thickness is 12 μm)) on which 10 × 10 lands (diameter: 1.4 mm, interval: 4.2 mm) are formed on one side On the other side, the package component mounting solder paste was printed with a metal squeegee. Next, the pin fixing solder paste was printed on the land with a metal squeegee. Pins (gold-plated (material: 42 alloy), shaft diameter: 0.3 mm, head diameter: 0.9 mm, length: 2.07 mm) are applied to the printed pin fixing solder paste. In the contact state, the substrate was heated under reflow condition A (FIG. 2) or reflow condition B (FIG. 3) to produce a PGA package substrate. Next, an IC chip was placed on the solder bumps of this PGA package substrate, and heated under reflow condition A (FIG. 2) or reflow condition B (FIG. 3) to produce a PGA package. About the obtained PGA package, pin stand property evaluation was performed on the following references | standards by visual observation.
○: No abnormality △: There is a pin that is slightly tilted ×: There is a pin that has fallen-: Since the solder did not melt completely, adhesion failure occurred between the pin and land

(Reflow heat resistance evaluation)
About each PGA package evaluated by the said pin stand property evaluation, reflow heat resistance evaluation was performed on the following references | standards by visual observation.
○: No abnormality ×: The base material is discolored

  As shown in Table 1, in the examples of the present invention, better results were obtained for any of the evaluation items as compared with the comparative examples. Therefore, according to the present invention, it has been confirmed that a pin grid array package can be provided in which deterioration of the base material due to the reflow process is suppressed and pin standability is excellent.

DESCRIPTION OF SYMBOLS 1 Base material 2 Terminal 3 Solder paste for package component mounting 4 Solder paste for pin fixing 5 Conductive connection pin 6 Conductive connection portion 7 Solder bump 8 Package component 10 PGA package substrate 20 PGA package

Claims (9)

Solder paste for pin grid array package,
Sn / Sb based lead-free solder powder and flux,
The Sn / Sb-based lead-free solder powder is a solder paste containing a first solder powder and a second solder powder having a melting point higher than that of the first solder powder. The first solder powder is composed of 3 to 7% by mass of Sb and the remaining Sn,
The solder paste according to claim 1, wherein the second solder powder is composed of 10 to 20% by mass of Sb and the remaining Sn.   The solder paste according to claim 1 or 2, wherein the Sn / Sb-based lead-free solder powder has an average particle size of 1 to 50 µm. A substrate for a pin grid array package having a substrate, terminals disposed on one side of the substrate, and conductive connection pins disposed on the terminals,
The board | substrate for pin grid array packages to which the said terminal and the said electroconductive connection pin were joined using the solder paste of any one of Claims 1-3.   The substrate for a pin grid array package according to claim 4, further comprising solder bumps formed on a surface opposite to a surface on which the conductive connection pins of the base material are disposed.   The substrate for a pin grid array package according to claim 4 or 5, and a package component mounted on a surface opposite to the surface on which the conductive connection pins of the substrate for a pin grid array package are disposed. Pin grid array package.   The pin grid array package according to claim 6, wherein a reflow temperature when mounting the package component is 230 ° C. or higher. A method for manufacturing a substrate for a pin grid array package having a base material, terminals disposed on one side of the base material, and conductive connection pins disposed on the terminal,
The manufacturing method of the board | substrate for pin grid array packages which joins the said terminal and the said electroconductive connection pin using the solder paste of any one of Claims 1-3.   The manufacturing method of the board | substrate for pin grid array packages of Claim 8 whose reflow temperature at the time of joining the said terminal and the said conductive connection pin is less than 250 degreeC.

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