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Electronic parts assembling and testing method, and electronic circuit baseboard manufactured by the method

a technology for electronic components and baseboards, which is applied in the direction of manufacturing tools, circuit inspection/indentification, and soldering apparatus, etc., can solve the problems of oxidation during soldering, the structural integrity of the structure is difficult to employ, and the additional problem of weakening the intensity of the solder connection section, so as to prevent oxidation

Inactive Publication Date: 2006-02-23
NEGISHI TAKASHI +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0016] In yet another embodiment, a coat made of highly heat resistant pre-flux is formed on the land of the electronic circuit baseboard so as to prevent oxidation during soldering.

Problems solved by technology

However, when an electronic circuit baseboard is soldered with an Sn—Pb type solder and the lead is discarded, the solder sometimes fuses out therefrom, giving undesirable effects to an ecological system and thereby causing environmental pollution.
Furthermore, since Sn-58 weight % Bi has a fusing point of 138C and is hard and brittle, this two component type alloy has problems associated with its structural integrity and is thus difficult to employ.
Sn-52 weight % In (indium) also has a low fusing point of 117° C. relative to Sn-37 weight % Pb which has a fusing point of 183° C. This difference in fusing point temperatures causes an additional problem of a weakening intensity in the solder connection section at high temperatures.
However, when seeking prescribed materials whose fusing points approximate 183° C., in the three component type Pb-free alloy, a perfect eutectic composition is not obtained.
Thus, when a flow soldering process is performed after parts are connected by a reflow soldering process, and air-cooling is performed without a blower for the baseboard, the respective temperatures decline at different rates in these added parts and the baseboard, As a result, a large temperature difference arises in the solder of the connecting sections since the connected parts have different heat capacities from that of the glass epoxy baseboard.
As a result, the connection strength of various parts which complete the segregation phase after receiving a reflow soldering process is readily weakened.
However, a melting point of the Su-Ag—Cu solder alloy is 217° C. and is still considerably higher than that of conventional Sn-37 mass % Pb having a melting point 183° C. Thus, when such a higher melting point solder is coated on a land, formed from a copper leaf of an electronic circuit baseboard, the copper leaf section is easily oxidized, and a wetting performance of such a solder is low.
As a result, there exists difficulty in testing electrical conduction of an electronic parts by contacting a tester to the land after soldering.

Method used

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  • Electronic parts assembling and testing method, and electronic circuit baseboard manufactured by the method
  • Electronic parts assembling and testing method, and electronic circuit baseboard manufactured by the method
  • Electronic parts assembling and testing method, and electronic circuit baseboard manufactured by the method

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first embodiment

[0045] Referring now to the drawings, wherein like reference numerals designate like elements throughout the several views, a first embodiment is now described with reference to FIGS. 6-8, and 12. Generally, a step of confirming quality of assembly is important for an electronic circuit baseboard after various parts are soldered thereto.

[0046] When conventional Pb based solder is utilized, below described errors are typically detected at the conclusion of the assembly process. Specifically, such errors may include, but are not limited to, erroneous wiring design, erroneous wiring, part misplacement / faulty orientation, erroneous parts mounting, malfunction of parts, defective connection caused by deformation of a parts lead terminal (i.e., parts lead), an open caused by shortage of solder during soldering, and short caused by excessive solder supplying. The same errors exist when the solder material is Pb free, as such, detection of errors in assembly yield important assurances for q...

second embodiment

[0056] A second embodiment is now described with reference to FIGS. 12A-12B and 13A-13B. FIGS. 12A and 12B illustrate conditions when a conventional solder material 102 including Pb is supplied and heated on a checker use land 101. Since a wetting performance of a conventional solder is fine, the solder can wet and spread to the entire checker use land during reflow soldering even if the solder is supplied only to a portion thereof as illustrated in FIG. 12A. Thus, a condition of the solder 103 can evenly thinly spread on the entire checker use land 101.

[0057] In contrast, FIGS. 13A and 13B illustrate a case when a cream solder excluding Pb is supplied to the test land. As illustrated in FIG. 13B, since a wetting performance of such a cream solder itself is relatively inferior, the cream solder stays in a section of the test land 111 where the cream solder 112 is supplied. Thus, prevention from forming an oxidation coat on the test land may be not entirely covered by such a solder a...

third embodiment

[0060] A third embodiment is now described with reference to FIGS. 2A-2D, FIGS. 2A and 2C each illustrating a side view, FIGS. 2B and 2D each illustrating a plan view. FIG. 2A-2D illustrate conditions when Pb free soldering is performed both in the atmosphere and inert ambient atmosphere. As there shown, numeral number 20 denotes an electronic part, numeral number 21 denotes a test land, numeral number 22 denotes a copper leaf section, and numeral numbers 23 and 23′ denote Pb free solder.

[0061] As illustrated in FIGS. 2A-2B, the Pb free soldering performed in the atmosphere may be inferior in a wetting performance and does not spread due to its surface tension. In contrast, the Pb free soldering performed in the inert ambient atmosphere may extraordinary suppress formation of an oxidation coat due to decreasing in a quantity of oxygen. Specifically, there exists an advantage that decreasing in a wetting performance of the Pb free material can be compensated by stoppage of oxidation ...

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Abstract

A method for assembling and testing an electronic circuit baseboard includes at least a step of soldering at least one electronic part to an electronic circuit baseboard using Pb excluded solder. One of erroneous wiring, erroneous mounting, malfunction, and defective soldering of the least one electronic part is tested by contacting a probe pin to various probe pin contact sections on the electronic circuit baseboard. During the step of soldering, the Pb excluded solder is also supplied to at least one of the various probe pin contact sections in order to suppress oxidation thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority under 35 USC §119 to Japanese Patent Application Nos. 2001-270597 and 2001-290198 filed on Sep. 6, 2001, and Sep. 21, 2001, respectively, the entire contents of which are herein incorporated by reference. BACKGROUND OF THE INVENTION [0002] The present invention relates to a method for assembling and testing electronic parts using Pb-free (lead-free) solder alloy, and an electronic circuit baseboard manufactured and tested by the method. [0003] In particular, the present invention relates to an electronic circuit baseboard assembling and testing method capable of precisely testing conduction of the parts using a test land while suppressing oxidation thereof. [0004] In the past, an Sn—Pb (tin-lead) type solder, including a large quantity of Pb (lead), is generally utilized when electronic parts are mounted. However, when an electronic circuit baseboard is soldered with an Sn—Pb type solder and the lead is ...

Claims

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Application Information

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IPC IPC(8): B23K31/12B23K1/012H05K1/02H05K3/34
CPCB23K1/012H05K3/3463H05K1/0268B23K2201/40B23K2101/40
Inventor NEGISHI, TAKASHIMUKAI, KATSUHIKONAKAGAWA, HIROMITSU
Owner NEGISHI TAKASHI