阅读说明：本技术 一种提高引线框架与塑封料结合力的方法 (Method for improving bonding force of lead frame and plastic package material ) 是由 陈中洲 方兆国 王子相 于 2021-09-07 设计创作，主要内容包括：本发明公开了一种提高引线框架与塑封料结合力的方法,属于半导体集成电路封装测试领域。包括以下步骤：步骤一、通过电火花将陶瓷劈刀中的键合丝末端熔融成球体；步骤二、通过键合压力,将所得球体于引线框架载体表面镀银层或内引脚镀银层上压扁,使焊点成型；通过超声电流处理,在焊点上产生促进键合的超声功率,使焊点与引线框架载体表面镀银层或内引脚镀银层形成键合界面；步骤三、将球体与键合丝的连接处切断,在引线框架载体表面镀银层或内引脚镀银层上形成焊点。其中,重复步骤一至步骤三,在引线框架载体表面镀银层上形成焊点阵列。本发明有效,解决了现有加工和使用过程中,容易出现分层进而导致器件失效的问题。(The invention discloses a method for improving the binding force of a lead frame and a plastic package material, and belongs to the field of semiconductor integrated circuit packaging test. The method comprises the following steps: firstly, fusing the tail end of a bonding wire in a ceramic cleaver into a sphere through electric sparks; secondly, flattening the obtained ball on the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin through bonding pressure to form a welding spot; generating ultrasonic power for promoting bonding on the welding spot through ultrasonic current treatment, so that a bonding interface is formed between the welding spot and the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin; and step three, cutting off the joint of the ball body and the bonding wire, and forming a welding spot on the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin. And repeating the first step to the third step to form a welding spot array on the silver coating on the surface of the lead frame carrier. The invention is effective, and solves the problem that the device is easy to be layered and further to be invalid in the existing processing and using processes.)

1. A method for improving the bonding force of a lead frame and a plastic package material is characterized by comprising the following steps:

firstly, fusing the tail end of a bonding wire in a ceramic cleaver into a sphere by electric sparks in a protective gas atmosphere;

flattening the obtained ball on the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin through bonding pressure to form a welding spot, and generating ultrasonic power for promoting bonding on the welding spot through ultrasonic current treatment to enable the welding spot and the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin to generate interface physical and chemical reaction to form a bonding interface;

and step three, cutting off the joint of the ball body and the bonding wire, and forming a welding spot on the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin.

2. The method of claim 1, wherein the steps one through three are repeated to form an array of solder bumps on the silver plating on the surface of the leadframe carrier or the silver plating on the inner leads.

3. The method for improving the bonding force of the lead frame and the plastic package material according to claim 2, wherein the array mode of the welding spot array can be square array or parallelogram array;

and locally arraying welding spots at fixed layered positions of the plastic package product or completely arraying welding spots at unfixed layered positions of the plastic package product.

4. The method of claim 2, wherein the leadframe carrier is de-oxidized after the array of pads is completed.

5. The method for improving the bonding force between the lead frame and the plastic package material according to claim 1, wherein in the first step, the current time parameter for fusing the end of the bonding wire in the ceramic cleaver into a sphere by electric spark comprises: the ball firing current is 60-65 mA, and the ball firing time is 350-380 mus.

6. The method for improving the bonding force between the lead frame and the plastic package material according to claim 1, wherein in the second step, the bonding pressure is 18-22 g.

7. The method for improving the bonding force between the lead frame and the plastic package material according to claim 1, wherein in the second step, the ultrasonic current is 75 to 85mA, and the time is 10 to 15 ms.

8. The method of claim 1, wherein the bonding wire is a copper wire.

9. The method for improving the bonding force of the lead frame and the plastic package material according to claim 1, wherein the method for improving the bonding force of the lead frame carrier or the inner pin and the plastic package material is performed by a K & S press welder.

Technical Field

The invention belongs to the field of semiconductor integrated circuit packaging test, and relates to a method for improving the binding force of a lead frame and a plastic packaging material.

Background

In the packaging process of semiconductor integrated circuit lead frame products, silver is generally plated on the surface of a copper lead frame in order to meet the lead bonding requirement, after a chip is bonded on the lead frame, a bonding wire is used for bonding a chip bonding pad and the silver plated layer of the lead frame to realize an electric path, and finally plastic packaging, electroplating, laser marking and molding are carried out.

However, due to the weak bonding force between silver and the plastic package material, delamination is likely to occur between the silver coating layer of the lead frame type plastic package product and the plastic package material under the action of stress in the subsequent product processing and using processes and the stress of the plastic package body, and once delamination occurs, the delamination becomes a path for moisture intrusion or a source of delamination expansion, and finally the plastic package device fails.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a method for improving the bonding force between a lead frame and a plastic package material, and solves the problem that the device is easy to be delaminated and further fails in the existing processing and using processes.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

the invention discloses a method for improving the binding force of a lead frame and a plastic package material, which comprises the following steps:

firstly, fusing the tail end of a bonding wire in a ceramic cleaver into a sphere by electric sparks in a protective gas atmosphere; flattening the obtained ball on the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin through bonding pressure to form a welding spot, and generating ultrasonic power for promoting bonding on the welding spot through ultrasonic current treatment to enable the welding spot and the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin to generate interface physical and chemical reaction to form a bonding interface; and step three, cutting off the joint of the ball body and the bonding wire, and forming a welding spot on the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin.

Preferably, the first step to the third step are repeated, and the welding spot array is formed on the silver coating on the surface of the lead frame carrier or the silver coating on the inner pin.

Further preferably, the array mode of the welding spot array can be a square array or a parallelogram array; and locally arraying welding spots at fixed layered positions of the plastic package product or completely arraying welding spots at unfixed layered positions of the plastic package product.

Further preferably, the leadframe carrier is subjected to a de-oxidation treatment after the array of solder joints is completed.

Preferably, in the first step, the current time parameter for fusing the end of the bonding wire in the ceramic cleaver into a sphere by the electric spark comprises: the ball firing current is 60-65 mA, and the ball firing time is 350-380 mus.

Preferably, in the second step, the bonding pressure is 18-22 g.

Preferably, in the second step, the ultrasonic current is 75-85 mA, and the time is 10-15 ms.

Preferably, the bonding wire is a copper wire.

Preferably, the method for bonding the lead frame carrier or the inner pin and the plastic package material is performed by a K & S press welder.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses a method for improving the binding force of a lead frame and a plastic package material, which is characterized in that a welding spot array is added on the interface of the original plastic package material and a silver coating on the surface of a lead frame carrier, thereby being beneficial to improving the binding force of the silver coating on the surface of the lead frame and the plastic package material. The welding spot array is added on the silver plating layer on the surface of the lead frame, so that the structure of a bonding interface between the lead frame and the plastic package material is changed, the strength of the bonding interface is improved, the layering problem between the copper lead frame and the plastic package material can be effectively improved, and the plastic package reliability is improved. In the process of array welding spots, the positions of the array welding spots can be flexibly selected, the welding spots are pertinently arrayed at fixed layered positions, the welding spots can avoid a chip bonding area and a lead bonding area, and the device is high in use flexibility and strong in adaptability. The method improves the bonding interface between the lead frame or the inner pin and the plastic package material by implanting welding spots on the lead frame carrier or the inner pin silver coating layer. Therefore, the method solves the problem that the device is easy to be layered and further fails in the existing processing and using processes.

Furthermore, the bonding wire is a copper wire, the bonding force between copper and the plastic packaging material is higher than that between silver and the plastic packaging material, and the bonding area can be increased by planting balls, so that the occurrence of layering is reduced finally, and the reliability of the product is improved.

Drawings

FIG. 1 is a schematic diagram of a ball firing link according to the present invention;

FIG. 2 is a schematic diagram of the process of forming a copper solder joint by bonding the copper solder ball interface according to the present invention; wherein, (a) is ball burning, (b) is positioning, (c) is molding, and (d) is cutting;

FIG. 3 is a schematic illustration of an array of braze spots (a partially square array of leadframe carriers) of example 1;

FIG. 4 is a schematic illustration of an array of braze dots (a partial parallelogram array of leadframe carriers) of example 1;

FIG. 5 is a schematic view of an array of braze joints (lead frame carrier in its entirety) of example 2;

fig. 6 is a schematic cross-sectional view of an array brazed ball molding of the present invention.

Wherein: 1-copper solder ball, 2-cleaver, 3-bonding wire, 4-copper lead frame carrier, 5-chip and 6-copper welding spot.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention is described in further detail below with reference to the accompanying drawings:

referring to fig. 1 to 2, the method for improving the bonding force between the silver coating on the surface of the lead frame and the molding compound disclosed by the invention comprises the following steps:

step 1, melting a reserved copper wire (bonding wire 3) of a ceramic chopper 2 into a copper solder ball 1 by electric sparks in a protective gas atmosphere for a certain current time;

step 2, flattening the copper solder ball 1 on the silver plating layer on the surface of the copper lead frame carrier 4 or on the silver plating layer of the inner pin under certain bonding pressure by adopting a ceramic cleaver 2 to form a copper solder joint 6; meanwhile, a certain ultrasonic current is applied to generate ultrasonic power for promoting bonding on the copper welding points 6, so that the copper welding points 6 and the silver coating on the surface of the copper lead frame carrier 4 or the silver coating on the inner pin generate interface physical and chemical reaction to generate intermetallic compounds to form a bonding interface;

step 3, cutting off a copper wire (bonding wire 3) along the tail part of the copper solder ball 1 by adopting a ceramic cleaver 2, and forming a copper welding spot 6 on the silver coating on the surface of the copper lead frame carrier 4 or the silver coating on the inner pin;

step 4, repeating the step 1, the step 2 and the step 3 to form a copper welding spot 6 array, wherein chip bonding and lead bonding positions are required to be reserved for copper welding spots 6 of the array; the copper welding point 6 array can increase the bonding area of the plastic packaging material and the lead frame interface, and copper with stronger bonding force with the plastic packaging material is used for partially replacing silver and forming the bonding interface with the plastic packaging material, so that the bonding force of the lead frame and the plastic packaging material can be finally improved.

Step 5, if the copper lead frame carrier 4 is excessively oxidized in the process of forming the copper welding spots 6, the copper lead frame carrier 4 can be subjected to deoxidation treatment;

step 6, carrying out chip bonding, plasma cleaning, lead bonding, plasma cleaning, plastic packaging, electroplating, laser marking and molding;

preferably, in the step 1, the copper solder ball is obtained by ball firing, the ball firing current is 60-65 mA, and the ball firing time is 350-380 mus.

Preferably, in the step 2, the bonding pressure is 18-22 g.

Preferably, in the step 2, the ultrasonic current for interface bonding is 65-75 mA, and the bonding time is 10-15 ms.

Preferably, in step 3, the array mode of the copper welding spots 6 array can be a square array or a parallelogram array. Among them, the area ratio of the rhomboid array circle which can form an angle of 60 ° is the largest, and the array is the densest parallelogram array.

Preferably, in step 3, the copper solder points 6 may be arrayed locally at the fixed layering positions of the plastic packaged product or not at the fixed layering positions.

Preferably, the processes described in step 1 to step 4 are performed on a K & S press welder.

Referring to fig. 3, it can be seen that when the invention is applied, a silver layer can be plated on the surface of the lead frame carrier to partially array square array welding spots so as to solve the problem of fixing and layering of the plastic package product.

Referring to fig. 4, it can be seen that when the invention is applied, a silver layer can be plated on the surface of the lead frame carrier to partially array the parallelogram array welding spots so as to solve the problem of fixing and layering of the plastic package product.

Referring to fig. 5, it can be seen that when the present invention is applied, all the array solder joints can be formed after the chip position is reserved on the silver coating layer on the surface of the lead frame carrier to solve the problem of non-fixed position delamination on the surface of the lead frame carrier of the plastic package product.

Referring to fig. 6, it can be seen that, due to the existence of the solder joints, the bonding area of the molding compound and the lead frame interface is increased, and the bonding force of the molding compound and the lead frame interface can be effectively improved.

The present invention is described in further detail below with reference to specific examples:

example 1:

for a certain model number LQFP48L (with chip attach carrier size 5.2*5.2mm²Chip size 3.2 x 4.2mm²And the carrier at the upper left corner of the chip is easy to layer) and the specific implementation conditions are as follows by utilizing the invention:

step 1: copper welding points 6 are arranged on the array of the upper left corner of the copper lead frame carrier 4, and the interval between the copper welding points 6 is 80 microseconds; this example produced a square array.

Specifically, the current time parameter for fusing the tail end of the bonding wire in the ceramic cleaver into a sphere through electric sparks is 60mA of sphere burning current, and the sphere burning time is 350 mu s; the parameter of the bonding pressure in the bonding process is 18 g; the operating parameters of the ultrasonic current treatment are ultrasonic current 65mA and ultrasonic time 10 ms.

Step 2: bonding the chip to be packaged to the designated position of the chip bonding carrier of the copper lead frame carrier 4;

and step 3: carrying out plasma cleaning on a circuit to be bonded, and then carrying out wire bonding according to a bonding diagram;

and 4, step 4: and (3) carrying out plasma cleaning on the bonded circuit, and carrying out plastic package by using a plastic package material for a plastic packaging machine to form a plastic package body.

And 5: and curing the plastic package body in an oven at 175 ℃ for 8-9 hours, and sequentially performing rib cutting, electrotinning, laser marking and forming on the plastic package body to obtain a finished plastic package part.

Example 2:

for a certain model LQFP44L (with chip bonding carrier size of 5.2 x 5.2 mm)²Chip size 5.2 x 5.2mm²And the carrier at the upper left corner of the chip is a product easy to layer), the specific implementation conditions are as follows by utilizing the invention:

step 1: reserving chip bonding positions on the carrier, and then arranging copper welding points 6 on all the arrays, wherein the distance between the copper welding points 6 is 100 mu s; in the embodiment, the copper welding spots 6 are locally arrayed at the fixed layered positions of the plastic package product to obtain a parallelogram array.

Specifically, the current time parameter for fusing the tail end of the bonding wire in the ceramic cleaver into a sphere through electric sparks is ball burning current 62mA, and the ball burning time is 360 mu s; the parameter of the bonding pressure during bonding was 19 g; the operating parameter of the ultrasonic current treatment is ultrasonic current 68mA and ultrasonic time 12 ms.

Step 2: bonding the chip to be packaged to the designated position of the chip bonding carrier of the copper lead frame carrier 4;

and step 3: carrying out plasma cleaning on a circuit to be bonded, and then carrying out wire bonding according to a bonding diagram;

and 4, step 4: and (3) carrying out plasma cleaning on the bonded circuit, and carrying out plastic package by using a plastic package material for a plastic packaging machine to form a plastic package body.

And 5: and (3) curing the plastic package body in an oven at 175 ℃ for 8-9 hours, and sequentially carrying out electrotinning, laser marking and rib cutting forming on the plastic package body to obtain a finished plastic package part.

Example 3:

for a certain model SOP8L (with chip bonding carrier size 2.4 x 3.3 mm)²Chip size 1.76 x 1.46mm²) The product, utilizing the invention, has the following concrete implementation conditions:

step 1: reserving chip bonding positions on the carrier, and then arranging copper welding points 6 on all the arrays, wherein the distance between the copper welding points 6 is 100 mu s; this example produced a square array.

Specifically, the current time parameter for fusing the tail end of the bonding wire in the ceramic cleaver into a sphere through electric sparks is ball burning current 65mA, and the ball burning time is 380 mu s; the parameter of the bonding pressure in the bonding process is 22 g; the operating parameters of the ultrasonic current treatment are ultrasonic current 75mA and ultrasonic time 15 ms.

Step 2: bonding the chip to be packaged to the designated position of the chip bonding carrier of the copper lead frame carrier 4;

and step 3: carrying out plasma cleaning on a circuit to be bonded, and then carrying out wire bonding according to a bonding diagram;

and 4, step 4: and (3) carrying out plasma cleaning on the bonded circuit, and carrying out plastic package by using a plastic package material for a plastic packaging machine to form a plastic package body.

And 5: and (3) curing the plastic package body in an oven at 175 ℃ for 8-9 hours, and sequentially carrying out electrotinning, laser marking and rib cutting forming on the plastic package body to obtain a finished plastic package part.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.