阅读说明：本技术 一种用于超小间距元件焊接的焊料及制备方法、焊接方法 (Solder for welding ultra-small-spacing element, preparation method and welding method ) 是由 潘明东 张中 陈益新 徐海 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种用于超小间距元件焊接的焊料及制备方法、焊接方法,焊料按重量份包括锡粉5～10份、普通助焊剂90-95份,焊接方法包括印刷、贴装、回流焊等步骤。本发明焊料中所含锡粉含量很少,焊接时能够有效降低短路风险,对超小间距元件表面贴装短路的改善有非常明显的效果,有效保证半导体产品封装,提升行业生产工艺能力。(The invention discloses a solder for welding an ultra-small spacing element, a preparation method and a welding method, wherein the solder comprises 5-10 parts of tin powder and 90-95 parts of common soldering flux by weight, and the welding method comprises the steps of printing, surface mounting, reflow soldering and the like. The solder contains less tin powder, can effectively reduce the short circuit risk during welding, has very obvious effect on improving the surface mounting short circuit of the ultra-small spacing element, effectively ensures the packaging of a semiconductor product, and improves the production process capability of the industry.)

1. The solder for welding the ultra-small spacing element is characterized by comprising 5-10 parts of tin powder and 90-95 parts of common soldering flux by weight.

2. The solder for ultra-small spacing element soldering of claim 1, wherein the tin powder is one or more of Sn96.6Ag3Cu0.5 and Sn96.5Ag3.5 alloys.

3. The solder for welding the ultra-small spacing element according to the claim 1 or 2, characterized in that the common soldering flux comprises 10-20 parts of resin, 5-10 parts of wetting agent, 2-10 parts of thixotropic agent, 40-70 parts of solvent, 10-15 parts of lactic acid-glycolic acid copolymer and 3-6 parts of phosphate monoester according to the weight part.

4. Solder for ultra-small pitch component soldering according to claim 1 or 2, wherein the solder is used for component pitch of 70 um.

5. A preparation method of solder for welding ultra-small-spacing elements is characterized in that 5-10 parts by weight of tin powder is added into 90-95 parts by weight of common soldering flux and uniformly stirred.

6. A soldering method using the solder for ultra-fine pitch component soldering of any one of claims 1 to 4, comprising the steps of:

the method comprises the following steps: printing the solder for welding the ultra-small spacing element on a welding pad of the circuit board by using a printing steel mesh with the thickness of 20-40 um;

step two: mounting the surface component at a designated printing position;

step three: and (3) completing the welding between the component and the welding pad by adopting a reflow soldering process, wherein the maximum temperature of the reflow soldering is set to be 240-250 ℃.

7. The welding method according to claim 6, wherein in the first step, the thickness of the printing steel net is 30 um.

Technical Field

The invention belongs to the technical field of semiconductor sealing and testing, and particularly relates to a manufacturing method of a welding flux for welding an ultra-small-spacing element and a welding method thereof.

Background

With the miniaturization of surface element distance in the semiconductor encapsulation industry along with the development of science and technology, the solder paste is adopted as the solder, and short circuit becomes a main defect after reflow.

The existing surface mounting process comprises the following steps: firstly, printing solder paste; secondly, mounting the surface mounting element at a position corresponding to the printing solder paste; and thirdly, welding the surface mounting element and the substrate welding pad by adopting a reflow soldering process. The tin paste used in the prior art mainly comprises tin powder and soldering flux, wherein the content of the tin powder is about 85-90%, and the tin powder is one of alloys such as Sn96.6Ag3Cu0.5 and Sn96.5Ag3.5; the flux content is about 10% to 15%.

When the pitch between the surface mount components is less than 75 μm, the solder paste is easily attached due to tension in a melted state due to a high content of the solder powder in the solder paste, thereby causing a short circuit.

Disclosure of Invention

The purpose of the invention is as follows: the invention provides a solder for welding an ultra-small spacing element, a preparation method and a welding method, aiming at solving the problem that the ultra-small spacing element is easy to cause short circuit in the welding process in the prior art.

The technical scheme is as follows: the solder for welding the ultra-small spacing element comprises 5-10 parts of tin powder and 90-95 parts of common soldering flux by weight.

Further, the tin powder is one or more of Sn96.6Ag3Cu0.5 and Sn96.5Ag3.5 alloys.

Further, the common soldering flux comprises, by weight, 10-20 parts of resin, 5-10 parts of a wetting agent, 2-10 parts of a thixotropic agent, 40-70 parts of a solvent, 10-15 parts of a lactic acid-glycolic acid copolymer and 3-6 parts of a phosphate monoester.

Further, the welding method is used for welding the element spacing of 70 um.

A preparation method of solder for welding ultra-small-spacing elements is characterized in that 5-10 parts by weight of tin powder is added into 90-95 parts by weight of common soldering flux and uniformly stirred.

A welding method using the solder for welding the ultra-small spacing element comprises the following steps:

the method comprises the following steps: printing the solder for welding the ultra-small spacing element on a welding pad of the circuit board by using a printing steel mesh with the thickness of 20-40 um;

step two: mounting the surface component at a designated printing position;

step three: and (3) completing the welding between the component and the welding pad by adopting a reflow soldering process, wherein the maximum temperature of the reflow soldering is set to be 240-250 ℃.

Further, in the first step, the thickness of the printing steel mesh is 30 um.

Has the advantages that: compared with the prior art, the solder for welding the ultra-small spacing element, and the manufacturing method and the welding method thereof provided by the invention have the advantages that the content of tin powder contained in the solder is less, the short circuit risk can be effectively reduced during welding, the effect of improving the surface mounting short circuit of the ultra-small spacing element is very obvious, the semiconductor product packaging is effectively ensured, and the industrial production process capability is improved.

Drawings

FIG. 1 is a flow chart of a welding method according to an embodiment;

FIG. 2 illustrates the soldering effect of the solder used for soldering of ultra-fine pitch components according to an embodiment;

fig. 3 is a graph comparing the soldering effect using the conventional solder paste.

Detailed Description

The invention is further explained below with reference to the figures and the embodiments.

The first embodiment is as follows:

the solder for welding the ultra-small spacing element comprises 5 parts of tin powder and 95 parts of common soldering flux by weight.

The tin powder is one or a mixture of several of Sn96.6Ag3Cu0.5, Sn96.5Ag3.5 and other alloys.

The common soldering flux comprises, by weight, 10-20 parts of resin, 5-10 parts of wetting agent, 2-10 parts of thixotropic agent, 40-70 parts of solvent, 10-15 parts of lactic acid-glycolic acid copolymer and 3-6 parts of phosphate monoester.

The solder terminals of the individual components cannot provide enough solder, and the solder can be complemented by the trace tin powder added in the solder provided by the application.

The resin is extracted from the secretion of trees, belongs to a natural product without corrosivity, and has activity in a liquid state to play a role in assisting welding.

The wetting agent can reduce the surface tension of the soldering flux and increase the wettability of the soldering flux to the soldering powder and the soldering pad.

The thixotropic agent can endow the soldering flux with certain thixotropic property, and the viscosity of the soldering flux is reduced under a stressed state so as to facilitate printing.

The solvent can dissolve solid components in the soldering flux to form a uniform solution.

The lactic acid-glycolic acid copolymer is capable of removing oxides on the bond pads and oxides on the bond tips of the fused component.

The phosphoric monoester has moisturizing and activity increasing effects.

The manufacturing method of the solder for welding the ultra-small spacing element comprises the following steps: and adding 5 parts by weight of tin powder into 95 parts by weight of common soldering flux, and uniformly stirring. Namely, the trace tin powder is added on the basis of the common soldering flux, and the manufacturing method is extremely simple.

A soldering method using the above solder for ultra-fine pitch component soldering, as shown in fig. 1, comprising the steps of:

s1: and printing the solder for welding the ultra-small-spacing element on a welding pad of the circuit board by using a printing steel mesh with the thickness of 20-40 um. Considering that the solder is diffused greatly during reflow, the thickness of the steel mesh can be reduced to reduce the consumption of the solder, and the diffusion range during reflow is reduced, so that the used printing steel mesh is thinner than the common solder paste printing steel mesh.

S2: surface components (such as resistors, capacitors, inductors, etc.) are mounted at designated printing positions.

S3: and (3) completing the welding between the component and the welding pad by adopting a reflow soldering process, wherein the highest temperature of the reflow soldering is set to be 240-250 ℃, and is reduced by about 15 ℃ compared with the highest temperature of the general reflow soldering. Because the solder contains less tin powder, the temperature required during welding is 15 ℃ lower than that of the solder paste, and the welding between the component and the welding pad can be realized.

The tin powder is in a molten state at the reflow soldering temperature, the higher the content of the tin powder is, the better the fluidity of the tin paste is, the larger the flow range of the tin paste with the same weight is, and under the condition of smaller spacing, the tin pastes with high tin powder content and good fluidity are in mutual contact and easily cause short circuit. The lower the content of the tin powder, the poorer the fluidity of the tin paste, and the less likely a short circuit will be caused. Too little tin powder content can result in weak or no solder joint. Experiments prove that when the content of the tin powder is 5-10%, short circuit is not easy to occur, and a good welding effect can be guaranteed.

The high integration product has 4 01005 elements in actual head to head mode and the elements are at ultra-small spacing (70 um), the solder of the example is used, the experiment is carried out by adopting a printing steel mesh with the thickness of 40um through the welding method of the embodiment, the actual production welding short circuit is reduced to be below 10ppm, and the welding effect is shown in fig. 2.

The contrast experiment adopts current No. 6 powder tin cream collocation 40um thickness steel sheet printing, and production welding short circuit is more than 10000ppm, and the welding effect is as shown in figure 3.

Example two:

the difference between the second embodiment and the first embodiment is that the solder for welding the ultra-small spacing element comprises 10 parts of tin powder and 90 parts of common soldering flux by weight. The manufacturing method comprises the following steps: adding 10 parts by weight of tin powder into 90 parts by weight of common soldering flux, and uniformly stirring. The other parts are the same as the first embodiment. The high integration product has 4 01005 elements in actual head to head mode and the elements are in ultra-small space (70 um), and the welding short circuit in actual production is reduced to below 10ppm by using the solder of the example and adopting a printing steel net with the thickness of 40um to carry out experiments through the welding method of the embodiment.

Example three:

the difference between the third embodiment and the first embodiment is that the solder for welding the ultra-small spacing element comprises 7 parts of tin powder and 93 parts of common soldering flux by weight. The manufacturing method comprises the following steps: and adding 7 parts by weight of tin powder into 93 parts by weight of common soldering flux, and uniformly stirring. The other parts are the same as the first embodiment. The high integration product has 4 01005 elements in actual head to head mode and the elements are in ultra-small space (70 um), and the welding short circuit in actual production is reduced to below 10ppm by using the solder of the example and adopting a printing steel net with the thickness of 40um to carry out experiments through the welding method of the embodiment.

Example four:

the difference between the fourth embodiment and the first embodiment is that the solder used for welding the ultra-small spacing element comprises 8 parts of tin powder and 92 parts of common soldering flux by weight. The manufacturing method comprises the following steps: adding 8 parts by weight of tin powder into 92 parts by weight of common soldering flux, and uniformly stirring. The other parts are the same as the first embodiment. The high integration product has 4 01005 elements in actual head to head mode and the elements are in ultra-small space (70 um), and the welding short circuit in actual production is reduced to below 10ppm by using the solder of the example and adopting a printing steel net with the thickness of 20um to carry out experiments by the welding method of the embodiment.

Example five:

the difference between the fourth embodiment and the first embodiment is that the solder used for welding the ultra-small spacing element comprises 9 parts of tin powder and 91 parts of common soldering flux by weight. The manufacturing method comprises the following steps: adding 9 parts by weight of tin powder into 91 parts by weight of common soldering flux, and uniformly stirring. The other parts are the same as the first embodiment. The high integration product has 4 01005 elements in actual head to head mode and the elements are in ultra-small space (70 um), and the welding short circuit in actual production is reduced to below 10ppm by using the solder of the example and adopting a printing steel net with the thickness of 30um for carrying out experiments by the welding method of the embodiment.