CN113923890B

CN113923890B - Circuit board mounting method and circuit board

Info

Publication number: CN113923890B
Application number: CN202111086236.8A
Authority: CN
Inventors: 杨磊磊; 胡珂珂; 梁如意
Original assignee: Kinwong Electronic Technology Longchuan Co Ltd
Current assignee: Kinwong Electronic Technology Longchuan Co Ltd
Priority date: 2021-09-16
Filing date: 2021-09-16
Publication date: 2022-09-27
Anticipated expiration: 2041-09-16
Also published as: CN113923890A

Abstract

The invention relates to the technical field of circuit board production, and provides a circuit board mounting method, which comprises the following steps: providing a substrate, wherein a first bonding pad and a second bonding pad are arranged on the substrate; mounting a nickel sheet on the first bonding pad; carrying out primary reflow soldering on the substrate; riveting the nickel sheet and the first bonding pad together; mounting an electronic component on the second bonding pad; and carrying out secondary reflow soldering on the substrate. The invention also provides a circuit board. According to the circuit board mounting method, the nickel sheet and the first bonding pad are riveted together before the substrate is subjected to secondary reflow soldering, so that the nickel sheet can be prevented from deviating due to movement of the nickel sheet, the weakening of the soldering strength of the nickel sheet and the first bonding pad can be prevented, and the failure of a soldering point between the nickel sheet and the first bonding pad can be avoided. The circuit board of the invention can effectively avoid the deviation of the nickel sheet and has higher quality of the finished circuit board.

Description

Circuit board mounting method and circuit board

Technical Field

The invention relates to the technical field of circuit board production, in particular to a circuit board mounting method and a circuit board.

Background

The lithium ion battery is considered as the most ideal power source of the new energy automobile due to the characteristics of high charge density and low weight. Because the lithium ion battery for the automobile is large in size and unstable in working property, and most of the lithium ion batteries are single batteries combined into a plurality of battery packs, the voltage and current working conditions of the lithium ion batteries need to be monitored. On the other hand, in order to obtain the maximum efficiency of the battery pack, it is necessary to fully charge and discharge all the batteries at the same time under the same voltage, so the time node of charging and the monitoring of the instantaneous power of the batteries are also necessary. Therefore, a special battery management system needs to be provided.

The battery management system is mainly responsible for detecting the voltage of each battery unit and the temperature of the battery pack, because both overvoltage and undervoltage conditions can cause thermal faults of the battery, once an overheating condition is detected, the control system needs to stop regenerative charging to reduce the power consumption of the battery pack, so that the temperature of a single battery is restored to a safe control range. In order to achieve the purpose, in the current new battery management system, a circuit board and an electronic component are often used as sensors to achieve the functions of voltage monitoring and temperature monitoring.

In the related art, a circuit board of an automobile battery management system needs to be provided with a nickel plate and electronic components, the nickel plate is used for being communicated with interfaces of different battery packs, and the components can play a role in adjustment and control. Due to the limitation of the circuit board structure, the nickel sheet needs to be mounted on the circuit board first, and the electronic component needs to be mounted on the circuit board through the first reflow soldering and then the second reflow soldering, so that the soldering strength between the nickel sheet and the circuit board is poor during the second reflow soldering, and the solder joint between the nickel sheet and the circuit board is seriously or even fails.

Disclosure of Invention

The invention provides a circuit board mounting method and a circuit board, which aim to solve the problems that when an electronic component is mounted on the circuit board through secondary reflow soldering, the soldering strength between a nickel sheet and the circuit board is poor, and even a soldering point is invalid.

An embodiment of the first aspect of the present application provides a circuit board mounting method, including:

providing a substrate, wherein a first bonding pad and a second bonding pad are arranged on the substrate;

mounting a nickel sheet on the first bonding pad;

performing primary reflow soldering on the substrate;

riveting the nickel sheet and the first bonding pad together;

mounting an electronic component on the second bonding pad;

and carrying out secondary reflow soldering on the substrate.

In some embodiments, a first through hole is disposed on the first pad on the substrate, and a second through hole is disposed on the nickel sheet; and riveting the nickel sheet and the first bonding pad together through riveting pieces penetrating through the first through hole and the second through hole.

In some of these embodiments, the rivet is electrically conductive.

In some embodiments, before mounting an electronic component on the second pad, the substrate is placed on a first carrier, the second pad is located on a side of the substrate away from the first carrier, and a first avoiding portion for accommodating an end of the rivet is provided on the first carrier.

In some embodiments, before the substrate is subjected to one reflow soldering, a reinforcing sheet is attached to a side surface of the substrate away from the first pad, and the shape and the position of the reinforcing sheet correspond to those of the first pad.

In some embodiments, attaching a reinforcing sheet to a side of the substrate away from the first pad includes:

coating thermosetting adhesive on the reinforcing sheet or the side surface of the substrate far away from one side of the first bonding pad, wherein the edge of the thermosetting adhesive is positioned inside the edge of the reinforcing sheet, and the distance between the edge of the reinforcing sheet and the edge of the substrate is greater than or equal to 0.1 mm;

attaching the reinforcing sheet to the side face of the substrate far away from one side of the first welding disc;

and pressing the reinforcing sheet and the substrate and curing at high temperature.

In some embodiments, before the nickel plate is mounted on the first pad, the substrate is placed on a second carrier, the first pad is located on a side of the substrate away from the second carrier, and a second avoiding portion for accommodating the reinforcing plate is arranged on the second carrier.

In some embodiments, the substrate is baked before a nickel plate is mounted on the first bonding pad.

In some embodiments, before the substrate is subjected to secondary reflow soldering, a cover plate is covered on the substrate, a groove is formed in the cover plate, the nickel plate and the first pad are both located in the groove, and the electronic component and the second pad are both located outside the groove.

Embodiments of the second aspect of the present application provide a circuit board manufactured by the circuit board mounting method according to the first aspect.

The circuit board mounting method provided by the embodiment of the invention has the beneficial effects that: because before carrying out secondary reflow soldering to the base plate, earlier nickel piece and first pad riveting together, so both can prevent that the nickel piece from taking place to remove the nickel piece off normal that leads to when the tin cream that once reflow soldering used melts once again between nickel piece and first pad, can prevent again that the tin cream that once reflow soldering used from taking place irregular flow after melting and arousing the soldering tin area not enough, lead to the welding strength weak of nickel piece and first pad, in addition, can also avoid the tin cream that once reflow soldering used to melt once again and take place the cold solidification, lead to the local too thick or local lack of tin cream on the first pad and make the solder joint between nickel piece and the first pad inefficacy.

According to the circuit board provided by the embodiment of the invention, the nickel sheet and the first bonding pad are riveted together in the manufacturing process, and then the substrate is subjected to secondary reflow soldering, so that the deviation of the nickel sheet is effectively avoided, the soldering strength of the nickel sheet and the first bonding pad is improved, and the quality of a finished product circuit board is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is a flow chart of a method of circuit board mounting in one embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a substrate without a nickel plate and electronic components mounted thereon according to an embodiment of the present invention;

fig. 3 is a cross-sectional view of the substrate at the first pad after riveting the nickel plate and the first pad together in one embodiment of the invention.

The designations in the figures mean:

10. a substrate; 11. a first pad; 111. a first through hole; 12. a second pad; 20. a nickel sheet; 21. a second through hole; 30. riveting the fastener; 40. a first carrier; 41. a first avoidance portion; 50. a reinforcing sheet; 60. tin paste; 70. a cover plate; 71. and (4) a groove.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings, which are examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In order to explain the technical solution of the present invention, the following description is made with reference to the specific drawings and examples.

Referring to fig. 1, fig. 2 and fig. 3, an embodiment of a first aspect of the present application provides a circuit board mounting method, including:

s10: a substrate 10 is provided, on which substrate 10 a first pad 11 and a second pad 12 are provided.

Specifically, the substrate 10 may be a flexible circuit board, and the first pad 11 and the second pad 12 are reserved on the substrate 10 during processing.

It is to be understood that one, two, or more than two of the first pads 11 and the second pads 12 may be provided.

As an implementation manner, a plurality of pads are disposed on the substrate 10, wherein a part of the pads are first pads 11, and another part of the pads are second pads 12, the first pads 11 are pads on which the nickel plate 20 is to be mounted, and the second pads are pads on which the electronic component is to be mounted.

S20: a nickel plate 20 is mounted on the first pad 11.

Specifically, the SMT (Surface mount Technology) solder paste 60 printer may be used to brush the solder paste 60 on the first pad 11, and then the automatic chip mounter is used to attach the nickel plate 20 to the first pad 11, where the solder paste 60 is located between the first pad 11 and the nickel plate 20, and a plurality of connection points are generated between the first pad 11 and the nickel plate 20, and these connection points may be used as subsequent solder joints.

Optionally, before the nickel plate 20 is mounted on the first bonding pad 11, the substrate 10 is baked to remove moisture absorbed by the substrate 10 during a previous processing procedure, so as to prevent the substrate from being exploded due to evaporation of the moisture in a reflow furnace after subsequent soldering.

Further, the nitrogen oven substrate 10 is used for baking treatment, and baking parameters are as follows: the baking temperature is 150-160 ℃, and the baking time is 90-120 min, for example, the baking temperature is 150 ℃, and the baking time is 120 min; or the baking temperature is 155 ℃, and the baking time is 105 min; or the baking temperature is 160 ℃, the baking time is 90min and the like.

Preferably, the baking temperature is 160 ℃ and the baking time is 120 min.

S30: the substrate 10 is subjected to one reflow soldering.

Specifically, the substrate 10 with the nickel sheet 20 mounted thereon is cured in a reflow tunnel oven, so that the solder joints between the first pads 11 and the nickel sheet 20 are reinforced.

Furthermore, the reflow tunnel furnace uses a nitrogen reflow tunnel, the nitrogen content is less than 1000PPM, such as 800PPM, 850PPM, 900PPM or 950PPM, the temperature of the constant temperature zone of the reflow furnace is controlled at 120-160 ℃, such as 120 ℃, 130 ℃, 140 ℃, 150 ℃ or 160 ℃, the time is 60-120 s, such as 60s, 70s, 80s, 90s, 100s, 110s or 120s, the time of the reflow zone is more than 200 ℃ for 15s-30s, such as 15s, 20s, 25s or 30s, the peak temperature of the temperature curve is 210-230 ℃, such as 210 ℃, 215 ℃, 220 ℃, 225 ℃ or 230 ℃, and the reflow curing effect is better.

S40: the nickel plate 20 and the first pad 11 are riveted together.

Specifically, after the nickel sheet 20 and the first bonding pad 11 are riveted together, relative movement between the nickel sheet 20 and the first bonding pad 11 in subsequent processes can be effectively avoided, dislocation of the nickel sheet 20 is avoided, irregular flowing of the solder paste 60 for one-time reflow soldering after melting can be prevented from causing insufficient solder area, the welding strength between the nickel sheet 20 and the first bonding pad 11 is weakened, in addition, cold solidification of the solder paste 60 for one-time reflow soldering after melting can be avoided, and the solder paste 60 on the first bonding pad 11 is locally too thick or locally lacks tin to cause failure of a welding point between the nickel sheet 20 and the first bonding pad 11.

As one practical way, the first pad 11 on the substrate 10 is provided with a first through hole 111, and the nickel sheet 20 is provided with a second through hole 21; the nickel sheet 20 and the first bonding pad 11 are riveted together by the riveting member 30 penetrating through the first through hole 111 and the second through hole 21, the structure is simple, and the nickel sheet 20 and the first bonding pad 11 can be tightly connected.

Specifically, the first through hole 111 can be processed by a punching device, and the second through hole 21 can be processed by a corresponding punching die, so that the process is simple and the processing is convenient.

Optionally, the apertures of the first through hole 111 and the second through hole 21 are both 2.0mm-2.2mm, such as 2.0mm, 2.1mm or 2.2mm, which can prevent the structure damage or strength reduction of the first bonding pad 11 and the nickel plate 20 caused by the too large apertures of the first through hole 111 and the second through hole 21, and can prevent the riveting member 30 with a larger diameter from being penetrated by the too small apertures of the first through hole 111 and the second through hole 21, resulting in the lower strength of the nickel plate 20 and the first bonding pad 11.

Further, the riveting member 30 has conductivity, so that the nickel plate 20 and the first bonding pad 11 can be tightly riveted, the electrical communication performance between the nickel plate 20 and the first bonding pad 11 can be enhanced, and the conduction characteristic from the nickel plate 20 to the first bonding pad 11 is enhanced.

Alternatively, the rivet 30 is an aluminum rivet or other similar conductive rivet.

S50: an electronic component is mounted on the second pad 12.

Specifically, the solder paste 60 may be applied to the second pad 12 by using an SMT (Surface mount Technology) solder paste printer, and then the electronic component may be attached to the second pad 12 by using an automatic placement machine, where the solder paste 60 is located between the second pad 12 and the electronic component, and a plurality of connection points are generated between the second pad 12 and the electronic component, and these connection points may be used as subsequent solder points.

Optionally, before mounting the electronic component on the second pad 12, the substrate 10 is placed on the first carrier 40, the second pad 12 is located on one side of the substrate 10 away from the first carrier 40, the first carrier 40 is provided with a first avoiding portion for accommodating the end of the riveting member 30, and the first avoiding portion 41 can be a groove or a hole, so that the smoothness of the substrate 10 can be ensured, the flatness of the surface of the substrate 10 when the electronic component is mounted is facilitated, and the accuracy of mounting the electronic component is improved.

S60: the substrate 10 is subjected to secondary reflow soldering.

Specifically, the substrate 10 with the electronic component mounted thereon is cured in a reflow tunnel oven, so that the solder joints between the second pads 12 and the electronic component are reinforced.

Furthermore, the temperature of the constant temperature area of the reflow oven is controlled to be 130-170 ℃, such as 130 ℃, 140 ℃, 150 ℃, 160 ℃ or 170 ℃, the time is 80-140 s, such as 80s, 90s, 100s, 110s, 120s, 130s or 140s, the time of the reflow area above 200 ℃ is 20s-35s, such as 20s, 25s, 30s or 35s, the peak temperature of the temperature curve is 210-230 ℃, such as 210 ℃, 215 ℃, 220 ℃, 225 ℃ or 230 ℃, and the reflow curing effect is better.

Because the substrate 10 is solidified in the reflow tunnel furnace, there is up-and-down hot air (as shown by the arrow in fig. 3), optionally, before performing the secondary reflow soldering on the substrate 10, the cover plate 70 is covered on the substrate 10, the cover plate 70 is provided with the groove 71, the nickel sheet 20 and the first pad 11 are both located in the groove 71, and the electronic component and the second pad 12 are both located outside the groove 71, so that the cover plate 70 can resist the high temperature on the front side of the substrate 10, thereby protecting the solder joint between the nickel sheet 20 and the first pad 11 from being melted by the secondary reflow high temperature, and avoiding the poor position deviation of the nickel sheet 20.

Alternatively, the cover plate 70 may be made of synthetic stone.

According to the circuit board mounting method provided by the embodiment of the invention, the nickel sheet 20 and the first bonding pad 11 are riveted together before the substrate 10 is subjected to secondary reflow soldering, so that the deviation of the nickel sheet 20 caused by the movement of the nickel sheet 20 when the tin paste 60 for primary reflow soldering between the nickel sheet 20 and the first bonding pad 11 is melted again can be prevented, the insufficient soldering tin area caused by irregular flowing after the tin paste 60 for primary reflow soldering is melted can be prevented, the soldering strength of the nickel sheet 20 and the first bonding pad 11 is weakened, and the cold solidification caused by the partial over-thickness or partial lack of tin of the tin paste 60 on the first bonding pad 11 to cause the failure of the welding point between the nickel sheet 20 and the first bonding pad 11 can be avoided.

Referring to fig. 1, fig. 2 and fig. 3 again, in some embodiments, before the substrate 10 is subjected to the reflow soldering, the reinforcing sheet 50 is attached to the side surface of the substrate 10 away from the first pad 11, and the shape and the position of the reinforcing sheet 50 correspond to the shape and the position of the first pad 11, that is, the shape of the reinforcing sheet 50 corresponds to the shape of the first pad 11, and the position of the reinforcing sheet 50 corresponds to the position of the first pad 11.

By adopting the above scheme, the substrate 10 can be reinforced to make strength support for subsequent high-temperature welding.

Optionally, the material of the reinforcing sheet 50 is FR4 (glass fiber epoxy resin), the thickness is 0.3mm, and the glass fiber epoxy resin sheet is cut into a predetermined size by using an automatic cutting machine, so as to obtain the reinforcing sheet 50.

As one practical aspect, the step of attaching the reinforcing sheet 50 to the side of the substrate 10 away from the first pad 11 includes:

firstly, thermosetting adhesive is coated on the reinforcing sheet 50 or the side surface of the substrate 10 far away from the first pad 11, the edge of the thermosetting adhesive is positioned inside the edge of the reinforcing sheet 50, and the distance between the edge of the reinforcing sheet 50 and the edge of the reinforcing sheet is greater than or equal to 0.1mm, so that the thermosetting adhesive is prevented from overflowing the edge of the reinforcing sheet 50 and being adhered to the substrate 10 after subsequent high-temperature pressing.

Specifically, the thermosetting adhesive can be made of acrylic acid and has a thickness of 50 μm, so as to prevent the thermosetting adhesive from overflowing the FR4 reinforcing shape after high-temperature pressing and adhering to the FPC.

Next, the reinforcing sheet 50 is attached to the side of the substrate 10 on the side away from the first pad 11.

Specifically, the reinforcing sheet 50 may be adhered to the side of the substrate 10 away from the first pad 11 and opposite to the first pad 11 by an automatic mounting machine.

Finally, the reinforcing sheet 50 and the base plate 10 are pressed and cured at high temperature.

Specifically, the reinforcing sheet 50 and the base plate 10 can be press-bonded using a fast press, wherein the temperature of the fast press is 160 ℃ to 180 ℃, such as 160 ℃, 165 ℃, 170 ℃, 175 ℃, or 180 ℃, the pressure is 100kg/c square meter-120 kg/c square meter, such as 100kg/c square meter, 105kg/c square meter, 110kg/c square meter, 115kg/c square meter, or 120kg/c square meter, and the pressing time is 120s to 150s, such as 120s, 125s, 130s, 135s, 140s, 145s, or 150 s.

The laminated reinforcing sheet 50 and the substrate 10 may be baked and cured at a high temperature by using an oven, wherein the baking and curing parameters are 150-160 ℃, such as 150 ℃, 152 ℃, 154 ℃, 156 ℃ or 160 ℃, and the curing time is 40-60 min, such as 40min, 45min, 50min, 55min or 60 min.

Optionally, a third through hole is formed in the reinforcing plate 50, and a fourth through hole is formed in the thermosetting adhesive, so that the rivet 30 is avoided.

Further, the aperture of third through-hole and fourth through-hole all is greater than the aperture of first through-hole 111 and second through-hole 21, if when the aperture of first through-hole 111 and second through-hole 21 was 2.0mm, the aperture of third through-hole and fourth through-hole was 2.2mm, so, conveniently penetrate first through-hole 111, second through-hole 21, third through-hole and fourth through-hole with rivet 30.

In addition, in order to ensure that the substrate 10 has good flatness when the nickel plate 20 is mounted subsequently, before the nickel plate 20 is mounted on the first bonding pad 11, the substrate 10 is placed on a second carrier, the first bonding pad 11 is located on one side of the substrate 10 away from the second carrier, and a second position-avoiding portion for accommodating the reinforcing plate 50 is arranged on the second carrier, and the second position-avoiding portion may be a hole or a groove.

Further, the second carrier is made of an aluminum alloy material, the thickness of the second carrier is 1.0 mm, and the width of the second carrier is consistent with the width of the conveyor line body of the reflow oven when the nickel sheet 20 is mounted.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.

Claims

1. A circuit board mounting method is characterized by comprising the following steps:

mounting a nickel sheet on the first bonding pad;

performing primary reflow soldering on the substrate;

riveting the nickel sheet and the first bonding pad together;

mounting an electronic component on the second bonding pad;

and carrying out secondary reflow soldering on the substrate.

2. The board mounting method according to claim 1, wherein a first through hole is provided on the first pad on the substrate, and a second through hole is provided on the nickel plate; and riveting the nickel sheet and the first bonding pad together through riveting pieces penetrating through the first through hole and the second through hole.

3. The method as claimed in claim 2, wherein the rivet is conductive.

4. The method as claimed in claim 2, wherein before the electronic component is mounted on the second pad, the substrate is placed on a first carrier, the second pad is located on a side of the substrate away from the first carrier, and the first carrier is provided with a first avoiding portion for accommodating an end of the rivet.

5. The method of claim 1, wherein a stiffener is attached to a side of the substrate away from the first pad before the substrate is subjected to the reflow soldering, and a shape and a position of the stiffener correspond to a shape and a position of the first pad.

6. The method for mounting a circuit board according to claim 5, wherein the step of attaching a reinforcing sheet to a side of the substrate away from the first bonding pad comprises the steps of:

attaching the reinforcing sheet to the side surface of the substrate far away from the first bonding pad;

7. The method as claimed in claim 5, wherein before the first bonding pad is mounted with the nickel plate, the substrate is placed on a second carrier, the first bonding pad is located on a side of the substrate away from the second carrier, and the second carrier is provided with a second avoiding portion for accommodating the stiffener.

8. The board mounting method according to any one of claims 1 to 7, wherein the substrate is baked before the first pad is mounted with the nickel sheet.

9. A method for mounting a circuit board according to any one of claims 1-7, wherein a cover plate is provided on the substrate before the substrate is subjected to the second reflow soldering, the cover plate is provided with a groove, the nickel plate and the first bonding pad are both located in the groove, and the electronic component and the second bonding pad are both located outside the groove.

10. A circuit board manufactured by the circuit board mounting method according to any one of claims 1 to 9.