JP2006032436A - Electronic device manufacturing method, soldering method, and heat shielding jig - Google Patents

Abstract

A low heat-resistant component having a heat resistant temperature of about 220 ° C. can be mounted even using solder having a high reflow temperature.
A heat shielding jig 20 including a heat absorbing member 11 is mounted on the surface mounting component 12 and soldered by loading and heating in a state where the heat absorbing member 11 is in contact with the surface mounting component 12.
[Selection] Figure 3

Description

  The present invention relates to a soldering method suitable for mixed mounting, particularly soldering using a Pb-free solder alloy with low toxicity, a heat shielding jig used therefor, and a method for manufacturing an electronic device using the same.

  Conventional methods for soldering to circuit boards such as organic substrates are broadly classified as follows: hot air is blown onto the circuit board, and solder paste printed on the electrodes is melted to solder the surface mount components. There are a reflow soldering process and a flow soldering process in which a molten solder jet is brought into contact with a circuit board to solder part of surface mount components such as insertion mounted components and chip components. These soldering methods are referred to as a mixed mounting method.

  In recent years, there has been a demand for using a Pb-free solder alloy with low toxicity for the solder used in this mixed mounting method (a solder paste in the reflow soldering process and a molten solder jet in the flow soldering process). Yes. This Pb-free solder alloy is applicable to the connection of electronic components to circuit boards such as organic substrates, and is an alternative to Sn-37Pb solder (unit: mass%) used for soldering at around 220 ° C. .

  As conventional techniques related to a mounting method using Pb-free solder, Japanese Patent Laid-Open Nos. 10-166178 (prior art 1), Japanese Patent Laid-Open No. 11-179586 (prior art 2), Japanese Patent Laid-Open No. 11-221694 (prior art). 3), JP-A No. 11-354919 (prior art 4), JP-A No. 2001-168519 (prior art 5), JP-A No. 2001-36233 (prior art 6), and the like are known.

  Prior art 1 describes Sn—Ag—Bi solder or Sn—Ag—Bi—Cu solder alloy as Pb-free solder. Prior art 2 describes connecting Sn-Ag-Bi solder, which is effective as Pb-free solder, to an electrode having a Sn-Bi layer on its surface. In Prior Art 3, the electronic component is composed of Sn as a main component on each of the first surface and the second surface of the organic substrate, Bi is 0 to 65 mass%, and Ag is 0.5 to 4.0. It is described that reflow soldering is performed with Pb-free solder containing 0 to 3.0% by mass of Cu, and / or In by mass%.

  Prior art 4 describes that in a method of connecting an electronic component and a circuit board using Pb-free solder containing Bi, the solder is cooled at a cooling rate of about 10 to 20 ° C./s. In the prior art 5, electronic parts are surface-mounted by reflow soldering on the A side of the board, and then the solder of the electronic parts inserted from the A side is flow soldered to the electrodes by flow soldering on the B side of the board. In the connection mounting method, the solder used for reflow soldering on the A side is Sn- (1.5 to 3.5 wt%) Ag- (0.2 to 0.8 wt%) Cu- (0 to 4 wt. %) In- (0 to 2 wt%) Bi, which is a Pb-free solder having a composition of Sn- (0 to 3.5 wt%) Ag- (0. 2 to 0.8 wt%) Pb-free solder composed of Cu.

  In prior art 6, when performing flow soldering using a Pb-free solder having a eutectic composition having a melting point higher than that of conventional Sn-37Pb, a heat conductive material is provided between the component main body and the substrate to provide solder. It is described that the temperature difference between the organic substrate and the electronic component main body is not increased when the substrate is cooled after being attached.

JP-A-10-166178 JP 11-179586 A JP-A-11-221694 Japanese Patent Laid-Open No. 11-354919 JP 2001-168519 A JP 2001-36233 A

  As shown in Table 1, Sn-Ag-Cu-In solder often used as Pb-free solder can be reflowed at a lower temperature as the In content increases. Can be suppressed.

その反面、Ｓｎ−Ａｇ−Ｃｕ−Ｉｎ系はんだはＩｎの含有量に応じて温度サイクル寿命が短くなる傾向にあり、−５５℃〜１２５℃、１サイクル／時間の条件の温度サイクル試験における１５００サイクル程度の温度サイクル寿命といった高い接続信頼性を実現するためには、Ｉｎの含有量を５％程度を限度として低く抑える必要がある（Ｉｎを含まないＳｎ−３Ａｇ−０．５Ｃｕの温度サイクル寿命は１８００サイクル程度）。

On the other hand, Sn-Ag-Cu-In solders tend to have a short temperature cycle life depending on the In content, and 1500 cycles in a temperature cycle test at -55 ° C to 125 ° C and 1 cycle / hour. In order to realize high connection reliability such as a temperature cycle life of about, it is necessary to keep the In content as low as about 5% (the temperature cycle life of Sn-3Ag-0.5Cu not containing In is About 1800 cycles).

  Therefore, the present invention provides a low heat-resistant component even when a solder having a high reflow temperature such as a Sn-3Ag-0.5Cu solder not containing In or a Sn-Ag-Cu-In solder having a low In content is used. It is an object of the present invention to provide a mounting component soldering method and a heat shielding jig that can be mounted, and an electronic device manufacturing method using them.

  In order to achieve the above object, in the present invention, a heat shielding jig provided with a heat absorbing member is mounted on a surface mount component and soldered by loading and heating in a state where the heat absorption member is in contact with the surface mount component. A soldering method is provided. It is desirable that the heat shielding jig used in the present invention further includes a height defining jig provided on the surface of the heat absorbing member that contacts the surface-mounted component. The solder bump height after soldering is desirably 65% or more and 95% or less of the solder bump height after soldering without mounting the heat shielding jig.

  Furthermore, in this invention, the heat shielding jig for soldering provided with a heat absorption member and the height prescription | regulation jig | tool provided in one surface of the front and back of this heat absorption member is provided. The heat absorbing member used in the present invention is preferably made of aluminum or an aluminum alloy.

  The present invention further includes a component mounting step of mounting the surface mount component on the circuit board, and the component mounting step includes a step of soldering the surface mount component to the circuit substrate using the soldering method of the present invention described above. A method for manufacturing an electronic device is provided. Processes other than the component mounting process are not particularly limited, and normal processes can be applied as they are.

  According to the present invention, it is possible to mount a low heat resistant component having a heat resistant temperature of about 220 ° C. even when using a solder having a high reflow temperature.

  In the present invention, for example, in a reflow soldering process in which a surface mount component 12 including a low heat resistance component (heat resistant temperature 220 ° C.) for bump connection is soldered on a circuit board 15 using a solder paste 14, FIG. As shown in a), the heat-absorbing member 11 that is a bulk material having a large heat capacity is placed on the upper surface of the package of the surface-mounted component 12 to be bump-connected, and brought into contact with the surface-mounted component 12, so that the external connection terminals 13 of the surface-mounted component 12 are connected. After the reflow soldering is performed on the substrate 15, the height of the solder bumps 16 of the surface mount component 12 after the reflow soldering as shown in FIG. The average solder bump height is 65% to 95%.

  If it is less than 65%, the bumps are excessively crushed by the package, and it becomes difficult to relieve the strain that the bumps cause between the substrate and the package of the low heat resistant parts. The partial fracture life may be significantly reduced.

  On the other hand, if it exceeds 95%, the mounted heat absorbing member 11 is too light (that is, the heat capacity of the bulk material is too small), so that the temperature of the bulk material rises rapidly during reflow soldering and sufficient heat is generated. It is often impossible to shield. Even when the heat absorbing member 11 having a sufficient heat capacity is used by using a height regulating jig or the like, if the sinking of the bump is small as described above, the bump height during reflow soldering is used. When there is no local constant, there is a moment when the bulk material is separated from the package at the place where the bump height is the lowest, so the bulk material cannot fully absorb the heat of the package and the heat shielding is insufficient. There is a case.

  In order to realize a bump height of 65% to 95% when this heat absorbing member 11 is not used, the heat shielding jig 20 shown in FIG. 2 can be used in the present invention. The jig 20 is placed on the surface mount component 12 as shown in FIG. 3A and solder reflow is performed, so that the height of the solder bumps 16 of the surface mount component 12 after reflow soldering is predetermined. 3 (preferably about 65% to 95% of the average solder bump height after reflow soldering without loading the bulk material 11) is provided in the jig 20 as shown in FIG. The sinking of the package is suppressed by the end of the height regulating member 21 being in contact with the substrate 15. Accordingly, in the present invention, the bump height and the height of the upper surface of the mounting component can be kept constant, and the mounting component can be prevented from being inclined.

  When using the jig 20 provided with such a height regulating member 21, even when the bump height exceeds 95% of the case where the bump height is not used, the mounted heat absorbing member 11 is too light (that is, the heat capacity of the bulk material). Is not too small), so there is no problem in terms of heat capacity.

  The heat absorbing member 11 of the heat shielding jig 20 is desirably made of aluminum or an aluminum-based alloy from the viewpoint of heat capacity. This is because aluminum or an aluminum-based alloy has a relatively large specific heat among metal materials and can absorb a lot of heat from a low heat-resistant component. In general reflow furnaces, substrates and parts are heated by using both an infrared heater and hot air, but aluminum or aluminum-based alloys have a high infrared reflectance similar to gold and silver, and are not conductive to the surface of the material. Since the state is formed, the state of the surface is hardly changed, and the cost is mentioned as an advantage.

  In addition, many heat-resistant parts with a heat-resistant temperature of around 220 ° C are small and have a small heat capacity. In many cases, the maximum temperature is reached in the circuit board when reflow soldering is performed. There are cases where it is not possible. For this reason, it is desirable that the heat absorbing member 11 be a bulk material having a certain height and volume. Further, the heat absorbing member may be placed on the upper surface of the component 12 (the surface opposite to the substrate) so as not to hinder the hot air of the reflow furnace flowing between the surface-mounted component 12 and the substrate 15 that perform bump connection. desirable.

  Hereinafter, although an embodiment of the present invention is described in detail using a specific example, the present invention is not limited to this. In addition, here, soldering by solder reflow has been described as an example, but the present invention is not limited to this, and can also be applied to the case of using other mixed mounting methods such as flow soldering.

  Full grid BGA (heat resistant temperature: 220 ° C., component size: 17 mm × 17 mm, bump pitch: 1 mm, bump number: 256, bump solder composition: Sn-37Pb), which is a low heat resistant component, is packaged with solder paste (composition: Sn -3Ag-0.5Cu-5In, supply thickness: 0.15 mm) 14 is placed on a printed circuit board 15, and an aluminum bulk material 11 (as a heat shielding jig 20) is placed on the package portion of the full grid BGA. (Size: 17 mm × 17 mm, thickness: 4 mm) and reflow soldering. The reflow conditions were such that reflow was possible with Sn-3Ag-0.5Cu solder paste. It is known that the average bump height is 0.75 mm when reflow is performed without mounting the bulk material 11 on the full grid BGA.

  For comparison, (1) when the full grid BGA is completely covered and a non-contact aluminum cover type heat shield jig with a thickness of 1 mm is used for the BGA, and (2) when no heat shield jig is used. Also, reflow soldering was performed.

  During soldering, the temperature profile was adjusted before soldering so that the package portion of the low heat resistant component (full grid BGA) 12 did not exceed the heat resistant temperature of 220 ° C. Table 2 shows the temperature of each part around the part during reflow soldering.

これによれば、カバー型熱遮蔽治具の使用は、低耐熱部品（フルグリッドＢＧＡ）のバンプ部の温度をできるだけ低下させずにパッケージ部の温度を低下させる効果が殆ど無く、治具を使用しない場合と殆ど差がないことがわかった。

According to this, the use of a cover-type heat shield jig has little effect on lowering the temperature of the package part without reducing the temperature of the bump part of the low heat-resistant component (full grid BGA) as much as possible, and the jig is used. It was found that there was almost no difference from the case of not doing.

  Therefore, when the jig is not used or when the cover type heat shield jig is used, when reflow soldering is performed at a temperature of the package portion below the heat resistant temperature of 218 ° C. to 219 ° C., the bump portion to be soldered is performed. Can reach only 216 ° C. to 217 ° C., and only a margin of 1 ° C. to 2 ° C. can be secured with respect to 215 ° C. which is the lowest temperature at which Sn-3Ag-0.5Cu-5In can be soldered (Table 1).

  On the other hand, when the bulk heat shielding jig 20 is used, the bump portion to be soldered reaches 222 ° C. to 223 ° C., and a margin of 7 ° C. to 8 ° C. is obtained.

  When the bulk heat shielding jig 20 is used, the solder bump height of the surface mount component after reflow soldering is 70% of the average solder bump height after reflow soldering without loading the bulk material. Thus, it was also confirmed that a normal connection shape that does not cause a significant decrease in connection reliability can be obtained.

  Full grid BGA reflow soldering was performed in the same manner as in Example 1 except that the shape of the heat shielding jig used was different. As shown in FIG. 2, the heat shielding jig 20 used in the present embodiment includes four columnar height regulating members 21 at the four corners of the lower surface of the heat absorbing member 11. 2A is a perspective view seen from the side of the upper surface, that is, the surface that becomes upper when loaded, and FIG. 2B is a perspective view seen from the side of the lower surface, that is, the surface that contacts the mounted component when loaded. is there.

  Also in the present embodiment, as in the first embodiment, the package portion of the full grid BGA is thermally shielded by the bulk heat absorbing member 11 loaded thereon. Further, in the present embodiment, unlike the case of the first embodiment, since the heat shielding member 20 includes the height defining member 21, the solder bump height of the surface-mounted component after the reflow soldering is determined based on the bulk material. When the height reaches 90% of the average solder bump height after reflow soldering without being stacked, the end of the jig 21 comes into contact with the substrate 15 to suppress the sinking of the package.

  In this example, for comparison with the result obtained in the first embodiment, soldering is performed so that the package portion of the low heat resistant component (full grid BGA) 12 has a heat resistant temperature of 218 ° C. The temperature profile was adjusted before. Table 3 shows the temperature of each part around the component during reflow soldering in this example.

この表からわかるように、実施例１で得られた結果と同様、本実施例の高さ規定部材２１を備える熱遮蔽治具２０を使用しても、はんだ付けが行われるバンプ部は２２３℃に到達し、Ｓｎ−３Ａｇ−０．５Ｃｕ−５Ｉｎはんだ付け可能最低温度に対して、８℃のマージンが得られる。

As can be seen from this table, similarly to the result obtained in Example 1, even when the heat shielding jig 20 including the height regulating member 21 of this example is used, the bump portion to be soldered is 223 ° C. And a margin of 8 ° C. is obtained for the lowest solderable temperature of Sn-3Ag-0.5Cu-5In.

  Moreover, when using the heat shielding jig 20 of the present embodiment, the solder bump height of the surface mount component after reflow soldering is equal to the average solder bump height after reflow soldering without loading the bulk material. It was also confirmed that a normal connection portion shape that does not cause a significant decrease in connection reliability was obtained.

It is explanatory drawing which shows the mounting method of the surface mounting components in Example 1. FIG. It is a perspective view which shows the external appearance of the heat shielding jig | tool in Example 2. FIG. FIG. 10 is an explanatory diagram illustrating an example of mounting surface-mounted components in Example 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Heat absorption member, 12 ... Surface mount component, 13 ... External connection terminal (solder bump), 14 ... Solder paste, 15 ... Circuit board, 16 ... Solder bump, 20 ... Heat shielding jig, 21 ... Height-defining member .

Claims (7)

  A soldering method, comprising: mounting a heat shielding jig including a heat absorption member on a surface mount component in a state in which the heat absorption member is in contact with the surface mount component and heating. The heat shielding jig is
The soldering method according to claim 1, further comprising a height defining jig provided on a surface of the heat absorbing member that contacts the surface-mounted component.   The soldering method according to claim 1 or 2, wherein the heat absorbing member is made of aluminum or an aluminum alloy.   The solder bump height after soldering is 65% or more and 95% or less of the solder bump height after soldering without mounting the heat shielding jig. The soldering method as described in any one. A heat absorbing member;
A heat shielding jig for soldering, comprising: a height defining jig provided on one of the front and back surfaces of the heat absorbing member.   6. The heat shielding jig for soldering according to claim 5, wherein the heat absorbing member is made of aluminum or an aluminum alloy. It has a component mounting process for mounting surface mount components on a circuit board.
The component mounting process
A method for manufacturing an electronic device, comprising the step of soldering the surface-mounted component to the circuit board using the soldering method according to claim 1.

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