JPH08222840A - Circuit board with electrode pad and its manufacture - Google Patents

Abstract

PURPOSE: To improve the adhesion between solder bumps and electrode pads to prevent insufficient connection even when a large heat cycle load acts on the bumps or pads by specifying the size of the central recessed sections of the pads. CONSTITUTION: After a photoresist layer 12 is formed over the entire surface of a ceramic substrate 11, recessed sections 15 >=3μm deep are formed on the layer 12 in an electrode pad forming pattern 18 and filled with conductor paste 16. Then only the dried bodies 17 of the conductor paste are left on the substrate 11 and the pattern 18 is formed by baking the dried bodies 17. After forming the pattern 18, electroless-plated layers 19 are formed as electrode pads 20. Finally, an LSI is connected to the substrate 11 through the pads 20 and conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board with an electrode pad and a method for manufacturing the same, and more particularly to a circuit board with an electrode pad which is excellent in connecting LSIs by a flip chip method and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, electronic devices have become higher in performance, smaller in size, and higher in density, and semiconductor devices mounted on these electronic devices are rapidly becoming multi-pin and multi-chip. . Accordingly, as the LSI bonding method, a wire bonding method or a TAB (Tape Au) method is used.
The flip chip method has been adopted more often than the tomated bonding method.
The flip chip method is a method in which a solder bump is further formed on a pad formed on one principal surface of an LSI and is connected to an electrode pad on the substrate side. (1) The connection length can be shortened and the electrical characteristics are good. . (2) Many pads can be formed without using a narrow pitch. (3) The ratio of LSI area / package area can be increased. (4) It has an advantage that the mounting thickness can be reduced.

As a method of forming the electrode pads for solder bump connection in the flip chip method on the ceramic substrate, there is a method of applying a conductor paste to the electrode pad forming portion by a screen printing method and performing a plating step after firing. In general, there is also a method of forming by a sputtering method, but the equipment cost and the production cost are extremely high, and are not actually used so much.

FIG. 3 is a schematic sectional view showing a state in which an LSI and a substrate are connected by a conventional flip chip method, and 23 in the drawing indicates a solder bump. The solder bump 23 is formed on the LSI 24 side,
Is the substrate 21 via the solder bumps 23 and the electrode pads 22.
It is connected with and is conducting. In this flip-chip connection process, the solder bump 23 is formed on the L
It includes a step of aligning the SI 24 so that the solder bump 23 is on the electrode pad 22 formed on the substrate 21, temporarily attaching it with a flux (not shown), and then melting the solder by a reflow process.

[0005]

The solder bumps 23 formed on the LSI 24 are melted and adhered to the LSI 24. However, due to the surface tension when the solder bumps 23 are melted, the shape of the solder bumps 23 is as shown in FIG. It becomes hemispherical (convex) as shown.

On the other hand, the electrode pad 22 on the substrate 21 is formed by the screen printing method, and also has a convex shape as shown in FIG.

Therefore, when the solder bumps 23 formed on the LSI 24 and the electrode pads 22 on the substrate 21 are temporarily attached to each other, there is a problem that the convex shapes collide with each other and the positions of the two easily shift. . Further, when the reflow process is performed in a state where the two are deviated from each other, the LSI 24 and the substrate 21 are connected in the state in which the positional deviation is left,
There is a problem that solder cracks may occur in the solder bumps 23 due to the temperature cycle, or cracks may occur in an electrode portion (not shown) on the LSI 24 side. Further, since the electrode pad 22 is formed by the screen printing method, there is a problem that the height of the electrode pad 22 is likely to vary and a connection failure with the solder bump 23 is likely to occur.

The present invention has been made in view of the above problems, and improves the adhesiveness between a solder bump and an electrode pad so that a defective connection portion between the solder bump and the electrode pad occurs even when a large thermal cycle load is applied. It is an object of the present invention to provide a circuit board with an electrode pad that can eliminate the problem and a method for manufacturing the same.

[0009]

In order to achieve the above object, a circuit board with an electrode pad according to the present invention is characterized in that it has an electrode pad having a recess of 3 μm or more in the central portion of the electrode pad. (1).

A method of manufacturing a circuit board with an electrode pad according to the present invention is the method of manufacturing a circuit board with an electrode pad described in (1) above, in which a photoresist layer is formed on a ceramic substrate or a ceramic green sheet. A photoresist layer forming step, a concave portion forming step of forming a concave portion in the photoresist layer in an electrode pad forming pattern, a conductor paste filling step of filling the concave portion with a conductor paste, and a conductor in the conductor paste by firing. And a baking step of baking the components on the ceramic substrate or on the ceramic green sheet.

A method of manufacturing a circuit board with an electrode pad according to the present invention will be described below with reference to FIGS.

First, as a photoresist layer forming step, a positive photoresist layer 12 is formed on a ceramic substrate 11 using a liquid photoresist (FIG. 1).
(A)).

The ceramic substrate 11 used in the present invention is not particularly limited as long as it can be used as a wiring substrate, and in addition to the alumina ceramic substrate usually used as a ceramic substrate, for example, a mullite ceramic substrate, glass, etc. Examples of the substrate include a ceramics substrate and an aluminum nitride ceramics substrate, which may be a substrate having wirings formed therein.

The ceramic green sheet used in the present invention can be formed by mixing the raw material powder of the ceramic substrate 11 with a resin, a solvent, a plasticizer, etc., and wiring etc. are formed inside. The ceramic green sheet may be used.

The photoresist layer 12 formed on the ceramic substrate 11 or the ceramic green sheet may be either a negative type or a positive type. When forming the positive type photoresist layer 12, first, a liquid positive type photoresist is formed on the surface of the ceramic substrate 11 or the ceramic green by a method such as a roll coater method, a bar coater method, a dip method or a Wheeler method (spinner method). After applying on the surface of the sheet, put the ceramic substrate 11 or the ceramic green sheet in an oven for about 87-90.
The photoresist is dried and solidified by heating in an oven or the like at 30 ° C. for about 30 to 40 minutes to form a positive photoresist layer 12. As the liquid photoresist,
For example, AZ4903, AZ46 manufactured by Hoechst Japan
20A, OP resists manufactured by Tokyo Ohka Kogyo Co., Ltd., Accutrace manufactured by Tokyo Electron, and Probimar manufactured by Ciba-Geigy Japan.

The photoresist layer 12 has a thickness of 10 to 50.
μm is preferred. The thickness of the photoresist layer 12 is 10μ
When the thickness is less than m, it becomes difficult to fill the conductive paste 16 in the recess 15 formed in the photoresist layer 12 in the subsequent step, while the thickness of the photoresist layer 12 is 50.
If the thickness exceeds μm, it becomes difficult to form a fine electrode pad pattern when the development process is performed in a later step. In order to uniformly form the 10 μm to 50 μm photoresist layer 12 on the ceramic substrate 11 using the liquid photoresist, the roll coater method or the bar coater method is more preferable among the coating methods. By using the liquid photoresist, the photoresist layer 12 formed on the ceramic substrate 11 is not significantly affected by the unevenness of the ceramic substrate, and the photoresist layer 12 having high flatness can be formed.

When forming the negative type photoresist layer 12, a liquid type negative type photoresist is used and the photoresist layer 12 is used in the same manner as in the case of the positive type photoresist.
Can be formed.

A dry film resist may be laminated on the ceramic substrate 11 or the ceramic green sheet. The dry film resist can be laminated by heating the ceramic substrate 11 or the ceramic green sheet to about 100 ° C. and thermocompressing the dry film resist. As the dry film resist, DuPont's product name Liston, Mitsubishi Rayon product Great dialon and so on.

Among the above photoresists, the liquid positive photoresist is most preferable because of its excellent resolution, no swelling in the developing process, and excellent adhesiveness to the ceramic substrate and the ceramic green sheet. .

Next, as a recess forming step, a method of forming the recess 15 in the photoresist layer 12 will be described.

Photoresist layer 1 formed on ceramic substrate 11 or ceramic green sheet
As a method of forming the concave portion 15 in 2, there are a method of using a photolithography method and a method of decomposing and eliminating the photoresist layer 12 by irradiation of a laser beam, but the size of the electrode pad 20 is usually 30 μm to 20 μm.
Since it is about 0 μm, a photolithography method capable of collectively forming recesses having a size in this range by a simple process is preferable. Here, the case of performing the photolithography method will be described.

The photoresist layer 12 is exposed to ultraviolet rays 14 or the like through a photomask 13 having a predetermined electrode pad forming pattern 18, and then is developed to form an electrode pad forming pattern 18 on the photoresist layer 12. The concave portion 15 is formed in a circular shape (FIG. 1C).

The condition of the exposure treatment with the ultraviolet rays 14 is not particularly limited, but the exposure amount is usually 700 to 800 mJ /
cm ² is preferred. The exposure dose is difficult to completely form the recess 15 reaching the surface of the ceramic substrate 11 by development is less than 700 mJ / cm ^2, happens when the other said exposure amount is more than 800 mJ / cm ² and over-exposure, the recess 15 This is not preferable because the cross-sectional shape of is an inverted trapezoid.

The conditions of the developing treatment are not particularly limited, and the developing treatment can be carried out by a commonly used method such as a spray method or an immersion rocking method.

After that, the photoresist layer 12 is heated at about 87 to 90 ° C. for 30 minutes so that the concave portion 15 of the photoresist layer 12 is not deformed when the conductive paste 16 is filled in a later step.
It is preferable to heat for about 40 minutes.

Next, as a conductor paste filling step, a conductor paste 16 for forming an electrode pad is filled in the recess 15 formed in the photoresist layer 12 (FIG. 1 (d)).

The conductor paste 16 for forming the electrode pad is composed of conductor powder, inorganic binding powder, resin and solvent, and the conductor component in the conductor paste 16 is a conductor powder known as an electrode material for ceramic wiring boards. However, specific examples thereof include Au, Ag, and Ag.
/ Pd, Cu, Ni, Mo, W and the like. Also,
The inorganic binding powder may be any one that has a function of adhering the electrode pad 20 to the ceramic substrate 11, and examples thereof include glass powder, ceramic powder, and metal oxide powder. Further, the above-mentioned resin may be a known resin used for ordinary conductor pastes, but when the photoresist layer 12 is removed by dissolution, a water-insoluble resin that does not dissolve during the dissolution removal is preferable. Specific examples of the resin include ethyl cellulose, acrylic resin, methacrylic resin and the like.

Further, as the solvent of the conductor paste 16, it is necessary to use one that does not dissolve the photoresist layer 12.
This is because when the conductor paste 16 is prepared using a solvent that dissolves the photoresist layer 12,
This is because when the second concave portion 15 is filled with the conductive paste 16, the positive photoresist layer 12 is dissolved in the solvent and the shape of the concave portion 15 is destroyed. Examples of the solvent that does not dissolve the photoresist layer 12 include hydrocarbon solvents having a low dielectric constant, such as toluene, xylene, camphor oil, turpentine oil, pine oil, phenylcyclohexane and dodecylbenzene.

The conductor paste 16 is applied to the photoresist layer 12
It is preferable that a squeegee (not shown) is used to fill the recess 15 and the conductor paste 16 is directly imprinted in the recess 15. The material of the squeegee is preferably rubber or Teflon. When the conductor paste 16 is left on the surface layer of the photoresist layer 12 other than the concave portion 15, it can be almost removed by scraping it off with a squeegee to which the conductor paste 16 is not attached. Further, when there is an extremely thin layer of the conductor paste 16 which cannot be removed by the above-mentioned operation, the conductor paste 16 is dried, and then a lapping film (alumina particles having a grain size of about 1 μm are adhered) is used. It may be removed by using. Further, when the filling failure of the conductor paste 16 occurs in the concave portion 15, the filling direction can be completely filled by converting the filling direction by 90 degrees from the initial filling direction and filling again.

The drying treatment after filling the conductor paste 16 is preferably carried out under the condition that the solvent is completely volatilized.
A heat treatment at 7 to 90 ° C. for about 10 to 20 minutes is preferable.

Next, a baking process is performed for the ceramic substrate 11 or the ceramic green sheet and the conductor formed in the electrode pad forming pattern 18 thereon. Before that, the photoresist layer 12 is erased. It is preferable to keep. Although it is possible to remove the photoresist layer 12 by burning it during the baking step, the photoresist layer 12 is difficult to burn, so that an unburned portion may remain after burning. The disappearance step of the photoresist layer 12 may be carried out by developing it with a solution that dissolves the photoresist layer 12 to dissolve and remove it. Examples of the solution for dissolving the photoresist layer 12 include alkaline aqueous solutions such as caustic soda water.

Although the case where the photoresist layer 12 is a positive type has been described above, when the photoresist layer 12 is a negative type, the photoresist layer 12 is formed on the ceramic substrate 11 or the ceramic green sheet by using a liquid negative type photoresist. It suffices to apply or laminate a negative dry film resist, and the filling of the conductor paste 16 can be performed by the same method and conditions as in the case of using the positive photoresist described above. Further, the step of eliminating the photoresist layer 12 is performed by treating the photoresist layer 12 filled with the conductor paste 16 with an alkaline solution to dissolve the photoresist layer 12 and removing the photoresist layer 12. The alkaline solution may be the same as when a positive photoresist is used.

By the above steps,
Only the dried body 17 of the conductor paste 16 remains on the ceramic substrate 11 or the ceramic green sheet (FIG. 1E). By baking this, the resin in the conductor paste 16 on the ceramic substrate 11 decomposes and disappears, the conductor powder contained in the conductor paste 16 sinters, and a predetermined electrode pad is formed on the ceramic substrate 11. The formation pattern 18 is formed (FIG. 1F). In addition, the conductor paste 16 on the ceramic green sheet
When the dried body 17 is formed, the ceramic green sheet and the conductor are simultaneously sintered, and a predetermined electrode pad forming pattern 18 is formed on the ceramic substrate 11. At this time, in addition to the electrode pad forming pattern 18, a signal line pattern, a ground pattern, a power pattern, etc. may be formed at the same time.

The firing conditions may be ordinary firing conditions. That is, the electrode pad forming pattern 18 made of the dried body 17 of the conductor paste 16 is formed on the ceramic substrate 11.
In the case of forming the conductor, the firing conditions for sintering the conductor are appropriate, and the conductor paste 16 is formed on the ceramic green sheet.
When the electrode pad forming pattern 18 made of the dried body 17 is formed, the firing condition in which the sintering of the ceramic green sheet and the sintering of the conductor are simultaneously performed is appropriate.

Further, the electrode pad forming pattern 18 is plated with Ni and Au (FIG. 1 (g)).
Is preferred. The plating method may be an electrolytic plating method or an electroless plating method. However, in the electrolytic plating method, it is necessary to previously form a lead wire for energizing the electrode pad forming pattern 18, and further, a step of cutting the lead wire after plating is required. Therefore, it is preferable to perform plating on the fine electrode pad forming pattern 18 by electroless plating. The electroless plating treatment can be performed by a known method and is not particularly limited.

[0036]

The circuit board with electrode pads according to the present invention has the electrode pad having a recess of 3 μm or more in the central portion of the electrode pad. Therefore, when connecting to the LSI by the flip chip method, The hemispherical solder bump can be easily aligned with the central portion of the electrode pad. Therefore, unlike the conventional case, the solder bumps are not connected while being displaced from the center of the electrode pads formed on the substrate side, and even if a large thermal cycle load is applied, the solder bumps and the electrode pads are not separated from each other. The connection will not be defective.

Further, since the shape of the electrode pad is concave, the contact area between the electrode pad and the solder bump is increased and the adhesiveness is improved.

Further, in the method for manufacturing a circuit board with electrode pads according to the present invention, the recess forming step of forming the recesses in the photoresist layer in the electrode pad forming pattern, and the conductor in the recesses. And a conductor paste filling step of filling a paste, when the conductor paste is filled in the recess formed in the photoresist layer, the central portion of the filling portion due to the surface tension of the conductor paste. And the central portion of the filling portion is further recessed when the solvent, which is a liquid component in the conductor paste, is volatilized, so that the shape of the electrode pad, which is a dried body of the conductor paste, is recessed. Therefore, the shape of the electrode pad is concave after the firing and the plating, and the circuit board with the electrode pad having the concave central portion according to the present invention can be manufactured.

Furthermore, since the thickness of the photoresist layer is uniform, there is almost no variation in the height of the electrode pad, and there is no defective connection with the solder bump.

[0040]

EXAMPLES AND COMPARATIVE EXAMPLES Circuit boards with electrode pads according to the embodiments of the present invention and methods for manufacturing the same will be described below with reference to the drawings.

Example 1 First, a liquid positive photoresist (AZ4903 manufactured by Hoechst Japan Co., Ltd.) was applied on the entire surface of a square (alumina) ceramic substrate 11 having a thickness of 2 mm and a side length of 50 mm by a bar coater method. Then, as a pre-baking treatment, this was put in an oven kept at 90 ° C. and dried for 30 minutes to form a photoresist layer 12 (FIG. 1A). The film thickness of the photoresist layer 12 after drying was 25 μm.

Next, a photomask 13 having a predetermined electrode pad pattern (diameter: circular shape of 100 μm, pitch between electrode pads; 250 μm) on the photoresist layer 12.
Through the UV, an exposure treatment with ultraviolet rays 14 was performed under the condition that the exposure amount was 700 mJ / cm ² (FIG. 1 (b)).

Next, a developing solution (40 made by Hoechst Japan)
Alumina ceramics substrate 11 having photoresist layer 12 in a solution in which 0K and water are mixed at a ratio of 1: 4)
Was dipped and developed by the dipping rocking method to form a recess 15 having an electrode pad forming pattern 18 in the photoresist layer 12 (FIG. 1C).

Next, as a conductive material, 85 wt% of copper powder, 3 wt% of lead borosilicate glass powder, and 3 wt of acrylic resin were used.
%, A (copper) conductor paste 16 containing 9 wt% of a solvent (pine oil) is used, and a small amount of this conductor paste 16 is placed on the photoresist layer 12 in which the concave portions 15 are formed, and a squeegee made of Teflon (size: 50 mm in length) , Width 100 mm,
(Thickness 3 mm) (not shown) is moved horizontally while being in contact with the surface of the photoresist layer 12, and the concave portion 15 of the photoresist layer 12 is rubbed and filled with the conductive paste 16 (FIG. 1D). . The squeegee moving speed at this time was set to 2.5 mm / sec. When the copper conductor paste 16 remained on the surface of the positive photoresist layer 12 other than the concave portions 15, it was scraped off with a Teflon squeegee to which the copper conductor paste 16 was not attached.

After that, the ceramics substrate 11 that has undergone the above-mentioned steps is put in an oven, and the conductor paste 16 filled in the recesses 15 is heated at 90 ° C. for 10 minutes to be dried, so that the solvent is volatilized and the conductor paste 16 in the conductor paste 16 is contained. The raw material powder was bound to the ceramic substrate 11. For the excess conductor paste (for example, a thickness of about 2 μm) that could not be removed by scraping with a Teflon squeegee, a photoresist layer was then used with a wrapping film (alumina having a grain size of 1 μm adhered as abrasive grains). The surface of 12 was polished and removed for about 10 seconds.

Next, the ceramic substrate 11 which has undergone the above-mentioned steps
Was immersed in a 3% aqueous solution of NaOH at room temperature for 1 minute and rocked to develop the photoresist layer 12 to dissolve and disappear, leaving only the dried body 17 of the conductor paste on the ceramic substrate 11 (see FIG. e)).

Next, the ceramic substrate 11 which has undergone the above-mentioned steps
By baking at 900 ° C. in a pure nitrogen gas atmosphere to decompose and eliminate the resin in the dried body 17 of the conductor paste, and burn the conductor on the ceramic substrate 11 to form the electrode pad forming pattern 18 (FIG. 1 (f)).

Next, on the surface of the electrode pad forming pattern 18, a Ni plating layer of 3.5 μm and an Au plating layer of 0.
Ni, A by electroless plating to 8 μm
An u electroless plating layer 19 was formed to form an electrode pad 20 (FIG. 1 (g)).

The plating layer forming step was performed by successively immersing the plating layer in a sensitizing solution and an activating solution, which are pretreatment solutions for plating, a Ni plating solution, and an Au plating solution. The samples taken from each solution were thoroughly washed with water and immersed in the next solution.

Example 2 (Alumina) green sheet was used in place of (Alumina) ceramic substrate 11,
The electrode pad 20 was formed in the same manner as in Example 1 except that a tungsten conductor paste was used as the conductor paste 16 and the firing temperature was set to 1550 ° C. in a nitrogen-hydrogen-steam atmosphere.

FIG. 2 shows Example 1 thus obtained.
7 is a schematic cross-sectional view showing a state in which an LSI is connected to the circuit board with electrode pads according to the second embodiment. The solder bumps 23 are formed on the LSI 24 side, and the LSI 24 is
It is connected to the ceramic substrate 11 via the solder bumps 23 and the electrode pads 20 to establish electrical continuity. When the shape of the electrode pad 20 was measured with a surface roughness meter, the depression in the central portion was 3 μm or more. The height variation of the electrode pad 20 was within ± 0.5 μm.

Here, the variation in the height of the electrode pad 20 is as follows. First, the height of the electrode pad 20 formed on each of the 20 samples manufactured according to the above-described example (made by Tokyo Seimitsu Co., Ltd.
The difference between the maximum value and the minimum value of the obtained electrode pad heights is obtained by measurement with the surfcoml 12B).

Next, the solder bump 2 made of Pb-5Sn
3 (bump height 100 μm), the LSI (chip size 9 mm × 9 mm) 24 is temporarily attached to the circuit board with electrode pads according to Example 1 and Example 2, and then reflow treatment (heating temperature 360 ° C.) is performed. Connected (Fig. 2).
On the other hand, as a heat cycle test, -45 ° C to 1
The relationship between the chip cumulative defect rate due to the increase in the connection resistance value and the test time was found under the temperature cycle of 1 cycle / 1 hour in the atmosphere of 00 ° C. As a result, the chip cumulative defect rate was 0% even after 5000 cycles. Met. In addition,
As a judgment of the chip failure, if even one of the solder bumps 23 in the LSI 24 observed a resistance increase of 0.05Ω or more (measurement current 1 mA), the LSI 24 was considered to be defective.

Comparative Example 1 On the other hand, in order to specifically compare with the case where the electrode pad is formed by the conventional method, as a comparative example, the electrode pad 22 is directly formed on the ceramic substrate 21 by the screen printing method. The one that formed is adopted.

That is, in Comparative Example 1, the conductor paste 16 used in Example 1 was used to form a pattern of the conductor paste 16 on the ceramic substrate 11 used in Example 1 by screen printing, and after firing, As in the case of No. 1, Ni plating and Au plating were applied.

The shape of the electrode pad 22 of the circuit board with electrode pads according to Comparative Example 1 thus obtained was measured with a surface roughness meter, and it was found that the central portion was 3 μm thicker than the peripheral portion.
It was raised and convex. The height variation of the electrode pad 22 was ± 3 μm.

When a thermal cycle test similar to that in Example 1 was conducted, the cumulative defective rate reached 100% by 1000 cycles.

Comparative Example 2 In Comparative Example 2, the pattern of the conductor paste 16 was formed on the green sheet used in Example 2 by the screen printing method using the tungsten paste used in Example 2, and after firing. In the same manner as in Example 2, Ni plating and Au plating were performed.

When the shape of the electrode pad 22 of the circuit board with electrode pads according to Comparative Example 2 thus obtained was measured with a surface roughness meter, the central portion was 2 μm thicker than the peripheral portion.
It was raised and convex. The height variation of the electrode pad 22 was ± 3 μm.

When a thermal cycle test similar to that in Example 1 was conducted, the cumulative defective rate reached 100% by 1000 cycles.

Comparative Example 3 In Comparative Example 3, titanium + molybdenum + is formed on the ceramic substrate 11 used in Example 1.
Using a sample made of copper, a conductor pattern was formed by a sputtering method, and Ni plating and Au plating treatment were performed as in the case of Example 1.

The shape of the electrode pad 22 of the circuit board with electrode pads according to Comparative Example 3 thus obtained was measured with a surface roughness meter, and the surface roughness was a rectangle having a smoothness of ± 0.5 μm or less. It was in shape.

When a thermal cycle test similar to that of Example 1 was conducted, the cumulative defective rate reached 100% by 3000 cycles.

As described above, in the circuit boards with electrode pads according to Examples 1 and 2, the height variation of the electrode pads 20 is uniformized to ± 0.5 μm, and even after a thermal cycle load is applied. The chip cumulative defect rate was 0%, and the connection with the solder bumps 23 was excellent. On the other hand, in the circuit boards with electrode pads according to Comparative Examples 1 and 2, since the electrode pads 22 are directly formed by the conventional screen printing method, the height variation of the electrode pads 22 is ± 3 μm.
m is large, and all those relating to Comparative Examples 1 to 3 are 10
The cumulative defective rate reached 100% in the cycle of 00 to 3000.

[0065]

As described above in detail, the circuit board with electrode pads according to the present invention has an electrode pad having a recess of 3 μm or more in the central portion of the electrode pad. When connecting with, it becomes easy to align the hemispherical solder bump with the central portion of the electrode pad. For this reason, the solder bumps are not displaced from the centers of the electrode pads formed on the substrate side and connected as in the conventional case, and the occurrence of a defective connection between the solder bumps and the electrode pads is prevented even during a thermal cycle load. be able to.

Further, since the shape of the electrode pad is concave, the contact area between the electrode pad and the solder bump can be increased and the adhesiveness can be improved.

In the method of manufacturing a circuit board with electrode pads according to the present invention, a recess forming step of forming recesses in the photoresist layer in the form of an electrode pad forming pattern, and filling the recess with a conductive paste. It includes a conductor paste filling step, and when the conductor paste is filled in the recess formed in the photoresist layer, the central portion of the filled portion is recessed due to the surface tension of the conductor paste,
Even when the solvent, which is a liquid component in the conductor paste, is volatilized, the central portion of the filling portion is further recessed, so that the shape of the electrode pad made of a dried body of the conductor paste is recessed. Therefore, the shape of the electrode pad is concave after the firing and the plating, and the circuit board with an electrode pad having a concave center portion according to the present invention having these characteristics can be manufactured.

Furthermore, since the thickness of the photoresist layer is uniform, there is almost no variation in the height of the electrode pad, and it is possible to eliminate any defective connection with the solder bump.

[Brief description of drawings]

1A to 1G are schematic cross-sectional views showing a method of manufacturing a circuit board with an electrode pad according to an embodiment of the present invention in the order of steps.

FIG. 2 shows an LSI for a circuit board with electrode pads according to an embodiment.
FIG. 3 is a schematic cross-sectional view showing a state in which is mounted.

FIG. 3 shows an LSI on a circuit board with electrode pads according to a comparative example.
FIG. 3 is a schematic cross-sectional view showing a state in which is mounted.

[Explanation of symbols]

 11 Ceramics Substrate 12 Photoresist Layer 15 Recess 16 Conductor Paste 18 Electrode Pad Forming Pattern 20, 22 Electrode Pad

Front Page Continuation (72) Inventor Kazushige Tanaka 2701-1 Iwakura, East Branch, Omine Town, Mine City, Yamaguchi Prefecture Sumitomo Metal Ceramics Co., Ltd.

Claims (2)

[Claims] 1. A circuit board with an electrode pad, comprising an electrode pad having a recess of 3 μm or more in the central portion of the electrode pad. 2. A photoresist layer forming step of forming a photoresist layer on a ceramic substrate or a ceramic green sheet; a concave forming step of forming concave portions in the photoresist layer in an electrode pad forming pattern; 2. The electrode pad according to claim 1, comprising a conductor paste filling step of filling a conductor paste, and a baking step of baking the conductor components in the conductor paste on the ceramic substrate or a ceramic green sheet by baking. Circuit board manufacturing method.