JP2807008B2 - Pb alloy solder with excellent thermal fatigue properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a Pb alloy brazing alloy having excellent thermal fatigue properties and creep resistance, and more particularly, to flipping when bonding electronic parts such as various electronic circuit boards and semiconductor parts. The present invention relates to a Pb alloy solder useful for bonding a semiconductor chip to a substrate by a chip bonding method or a tape carrier bonding method.

(Prior art and its problems) Conventionally, in order to produce a Pb alloy solder having excellent thermal fatigue properties, it has been necessary to reduce the oxygen content as an inevitable impurity in a Pb alloy base material to which a required element has been added to a low value. It has been considered effective to reduce the average crystal grain size.

However, heat cycle tests (150 to -50
(° C.), it was confirmed that the propagation of cracks caused by the thermal expansion strain of the joining material occurred along the crystal grain boundaries of the material.

Thus, it has been found that the reinforcement by suppressing the grain boundary slip in the crystal grain boundary portion is effective for improving the thermal fatigue characteristics and the creep resistance. Although Pb alloy brazing has excellent bondability, improvement in creep resistance is required. If the creep resistance is weak, the bonding layer is damaged due to the occurrence of voids or the like due to the displacement of the Pb alloy solder. An object of the present invention is to provide a Pb alloy braze having a component composition excellent in such thermal fatigue characteristics and creep resistance.

(Technical Means for Solving the Problems) The Pb alloy brazing according to the present invention comprises Sn: Pb containing 1 to 60 wt%.
The alloy substrate contains Sb: 0.01 to 10 wt% and Ni: 0.1 to 2.0 wt%, and contains Au, Ag, Pt, Pd, Mg, Ca, Li, In, Ce, Cd, Co, Cr, Fe, M
One or more of n, Se, Te, and Zr are contained in an amount of 0.1 to 5.0 wt%.

The inclusion of 1 to 60 wt% of Sn as a Pb alloy base material selects a general composition range as a solder (brazing) material.

By adding Sb to this PbSn substrate,
A crystal grain boundary portion formed by the SbSn compound is formed. If the Sb content is less than 0.01 wt%, the amount of the SbSn compound deposited is small and the desired effect cannot be obtained. If the Sb content exceeds 10 wt%, the SbSn compound is excessively precipitated and the grain size is excessive. It is bent out not only in the boundary part but also in the matrix part, causing hardening and embrittlement.

Therefore, the content of Sb is selected in the range of 0.01 to 10 wt%.

In order to deposit the intermetallic compound on the PbSn substrate, Sn
And elements that are easy to form compounds are added and contained as Ni, Au, Ag, Pt, Pd, Mg, Ca, Li, In, Ce, Cd, Co,
There are Cr, Fe, Mn, Se, Te, and Zr, and a compound of these elements and Sn is protruded as an intermetallic compound in a grain boundary portion made of the SbSn compound, and the compound particles are dispersed. This improves the thermal fatigue properties and creep resistance of the PbSn substrate.

As a specific means for dispersing and depositing the intermetallic compound particles, among the above-mentioned element group, Ni: 0.1 to 2.0 wt%, and Au, Ag, Pt, Pd, Mg, Ca, Li, In, Ce, Cd, Co, Cr, Fe, Mn,
This can be achieved by forming a composition containing 0.1 to 5.0 wt% of one or more of Se, Te, and Zr.

Ni content is less than 0.1 wt%, or Au, Ag, Pt, P
If the content of one or more of d, Mg, Ca, Li, In, Ce, Cd, Co, Cr, Fe, Mn, Se, Te, and Zr is less than 0.1 wt%, the intermetallic compound precipitates. Predetermined effect cannot be obtained due to small amount, Ni content is 2.0w
t% or Au, Ag, Pt, Pd, Mg, Ca, Li, In, Ce, C
The content of one or more of d, Co, Cr, Fe, Mn, Se, Te, Zr
If it exceeds 5.0% by weight, a dispersion form of the intermetallic compound cannot be obtained, and at the same time, eccentricity occurs and causes hardening and embrittlement.

 Therefore, the content of the above elements is selected within the above-mentioned range.

(Example) FIG. 1 is a structural diagram of a Pb alloy brazing alloy of the present invention. As shown in FIG. Is in a state in which intermetallic compound particles composed of are intermittently dispersed.

FIG. 2 is an actual micrograph of a Pb alloy solder. In FIG. 2, it is recognized that the intermetallic compound is precipitated in a dispersed state in the grain boundary part.

3 to 5 show micrographs of a comparative example having no component composition of the present invention. FIG. 3 shows Pb2Sn, and FIG. 4 shows Pb2S.
n0.5Sb, FIG. 5 shows Pb2Sn1Au.

In the case of Pb2Sn in FIG. 3, no grain boundary is formed, and in Pb2Sn0.5Sb in FIG. 4, a grain boundary (SbSn compound) is formed. No compound was formed, and it was confirmed that in Pb2Sn1Au in FIG. 5, the grain boundary was formed by the precipitation of the AuSn compound, but no precipitation of the intermetallic compound was observed.

Next, the following table shows the test results of preparing samples of Pb alloy solder having different component compositions and performing a heat cycle test using each sample.

As shown in Fig. 6, the heat cycle test showed that each sample
A NiCo plate and a Cu plate (each plated with Ni) were joined, and the number of heat cycles until peeling occurred at a heat cycle condition of 150 ° C. → RT → −50 ° C. was measured.

Regarding the superiority of the thermal fatigue characteristics, it was determined that the thermal cycle number was excellent when the number of thermal cycles was 250 or more.

Further, a creep resistance test was performed by the following method.

First, a Pb alloy solder having the composition shown in the table obtained by casting was machined into a plate-shaped test piece having a parallel portion having the following dimensions.

Specimen dimensions; thickness 2mm, width 10mm, length 35mm Parallel part width 4mm, parallel part length 16mm The test piece was left at room temperature for one month to remove residual stress and stabilize the structure, then creep Tested.

The creep test was performed using a motor-driven tensile tester equipped with a thermostat. The test temperature was 100 ° C. and the applied stress was 1 MPa. The elongation of the test piece was measured by measuring the elongation of the test piece gauge distance.

A creep test was performed for each test piece for 100 hours, and the results were shown in the table after being converted into the amount of strain per second.

Incidentally, regarding the above component composition, Mg, Ca, Li, In, Ce, Cd, Co, Cr,
Although the measured data of Fe, Mn, Se, Te, and Zr are not shown, they are omitted because they have characteristics similar to those shown in the table in relation to Sn.

(Effect) According to the present invention, the intermetallic compound is dispersed in the crystal grain boundary portion of the Pb alloy brazing, so that the intergranular slip at the grain boundary portion is suppressed, and the thermal fatigue characteristics and the creep resistance are excellent. Pb
Alloy brazing could be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged structural view of a main part of the Pb alloy brazing alloy of the present invention, FIG. 2 is a micrograph showing the metallographic structure, and FIGS. The micrograph shown in FIG. 6 is a cross-sectional view of a sample in a heat cycle test.

Claims (1)

(57) [Claims] 1. A Pb alloy substrate containing Sn: 1 to 60 wt%, wherein Sb:
Au, A containing 0.01 to 10 wt% and Ni: 0.1 to 2.0 wt%
g, Pt, Pd, Mg, Ca, Li, In, Ce, Cd, Co, Cr, Fe, Mn, Se, Te, Zr 1
A Pb alloy braze containing 0.1% to 5.0% by weight of one or more kinds and having excellent thermal fatigue properties and creep resistance.