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Reflow soldering method using Pb-free solder alloy and hybrid packaging method and structure

Inactive Publication Date: 2006-10-26
HITACHI LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006] Further, the hybrid mounting method needs to reflow solder the low heat resistant electronic component on the surface of the circuit board and flow solder the same to leads of an electronic component inserted from the surface of the circuit board by using Pb-free solder. Also during the flow soldering, it is necessary to prevent peeling of the low resistant electronic component by the re-melting of the reflow solder and not to degrade reliability after soldering connection.
[0026] Further, the invention can provide an effect of facilitating the temperature control in the hybrid mounting of surface mounting components including the low heat resistant electronic component such as FPGA and insertion mounting components by using the Pb-free solder alloy since the allowable range of the temperature for the jet flow of the molten solder can be extended to a high temperature side upon flow soldering.

Problems solved by technology

However, the prior arts 1 to 6 described above do not take into sufficient consideration the hybrid mounting method that meets such necessary subjects by using the Pb-free solder.

Method used

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  • Reflow soldering method using Pb-free solder alloy and hybrid packaging method and structure
  • Reflow soldering method using Pb-free solder alloy and hybrid packaging method and structure
  • Reflow soldering method using Pb-free solder alloy and hybrid packaging method and structure

Examples

Experimental program
Comparison scheme
Effect test

first example

[0050] In a first example, a generally used glass epoxy board 1a was used as a circuit board 1. The glass epoxy board has a thickness of about 1.6 mm, a length of about 350 mm, and a width of about 350 mm. It is provided on its board surface with a copper foil having a thickness of about 18 μm, and has through holes each having an inner diameter of 1 mm and a Cu pad diameter of about 1.6 mm formed at a density of about 0.7 N / cm2.

[0051] A QFP-LSI 2a of 32 mm square was used as a surface mounting pad 2. It has a lead pitch of about 0.5 mm and a lead width of about 0.2 mm and is provided with 208 leads made of 42 alloy subjected to Sn-10 mass % Pb plating.

[0052] Then, the QFP-LSI 2a of 32 mm square was flow soldered to the upper surface of the glass epoxy board 1a by 10 types of In-incorporated solder pastes of Sn-3Ag-0.5Cu-xIn (0≦x≦9, unit: mass %) (details are shown in the following Table 1).

TABLE 1Solder compositionSolidus temperatureLiqiudus temperature(mass %)(° C.)(° C.)Sn—3A...

second example

[0064] A second example is different from the first example in that a fluid such as nitrogen was blown to the upper surface 101 of the circuit board 1 for cooling as shown in FIG. 2 at about 20° C. to 50° C. at a flow rate of about 0.5 m3 / min. In FIG. 5, the temperature of the molten solder in the flow soldering bath is indicated on the abscissa and the In content of the solder used for the connection of QFP-LSI is indicated on the coordinate, and conditions causing no breakage is shown by symbol “◯” and the condition causing breakage is shown by symbol “X”. Further, the solid line in FIG. 5 is a line to be considered as a boundary between the conditions causing breakage and the conditions not causing the breakage.

[0065] The results of an experiment in the second example as shown in FIG. 5 confirm that the upper limit of the temperature of the flow molten solder can be increased by about 10° C. or less compared with the first example shown in FIG. 4. Further, the results of the exp...

third example

[0066] In a third example, as shown in FIG. 2, a fluid such as nitrogen at about 20° C. to 50° C. was blown for cooling at a flow rate of about 1.2 m3 / min by a board cooling device 6 in the second example. In FIG. 6, the temperature of the molten solder in the flow soldering bath is indicated on the abscissa and the In content in the solder used for the connection of QFP-LSI is indicated on the abscissa, and the condition not causing breakage is indicated by symbol “◯” and the condition causing the breakage is indicated by the symbol “X”. Further, the solid line in FIG. 6 is a line considered to be a boundary between the conditions causing breakage and the conditions not causing the same.

[0067] The results of the experiment for the third example as shown in FIG. 6 confirm that the upper limit for the allowable melting temperature of the flow solder can be increased by about 15° C. compared with the first example shown in FIG. 4. Further, the results of the experiment shown in FIG. ...

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Abstract

A hybrid mounting method using a Pb-free solder alloy including a reflow soldering step of soldering a surface mounting component 2 to at least the upper surface of a circuit board 1 using a Pb-free solder paste comprising an alloy based on Sn-(1-4)Ag-(0-1)Cu-(7-10)In (unit, mass %)-based alloy, an insertion step of inserting a lead or a terminal of an insertion mounting component 5 into a through hole perforated through the circuit board 1 from the upper surface thereof, a flux coating step, a preheating step, and a flow soldering step of spraying a jet flow 3 of Pb-free solder to the lower surface of the circuit board 1 preheated by the preheating step, thereby flow soldering the lead or the terminal of an insertion mounting component 5 to the circuit board.

Description

TECHNICAL FIELD [0001] The present invention relates to a reflow soldering method using a Pb-free solder alloy with less toxicity, and a hybrid mounting method, as well as a hybrid mounting structure. BACKGROUND ART [0002] When an electronic component is mounted by soldering on a circuit board such as an organic board, use of a Pb-free solder alloy with less toxicity has been demanded. [0003] The prior art relating to the mounting method using Pb-free solder is known from JP-A-10-166178 (prior art 1), JP-A-11-179586 (prior art 2), JP-A-11-221694 (prior art 3), JP-A-11-354919 (prior art 4), JP-A-2001-168519 (prior art 5), JP-A-2003-46229 (prior art 6), etc. [0004] The prior art 1 describes, as the Pb-free solder, an Sn—Ag—Bi series solder or an Sn—Ag—Bi—Cu series solder alloy. The prior art 2 describes connection of the Sn—Ag—Bi series solder effective as the Pb-free solder with an electrode provided on its surface with an Sn—Bi series layer. The prior art 3 describes reflow solderin...

Claims

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Application Information

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IPC IPC(8): C22C13/00H01L21/60H05K3/34
CPCB23K35/262C22C13/00H05K3/3415H05K2203/1572H05K3/3463H05K3/3468H05K2203/111H05K3/3447Y02P70/50H05K3/34
Inventor NAKATSUKA, TETSUYATAKANO, NOBUHIDESUGAHARA, TADAYUKIOMURA, TOMOYUKISAEKI, TOSHIOSERIZAWA, KOUJIISHIHARA, SHOUSAKU
Owner HITACHI LTD
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