CN112292021B

CN112292021B - Method for improving insertion and welding precision of PCB (printed circuit board) antenna

Info

Publication number: CN112292021B
Application number: CN202011170475.7A
Authority: CN
Inventors: 阳荣军; 曾科; 谭喜平
Original assignee: MFS TECHNOLOGY (HUNAN) CO LTD
Current assignee: MFS TECHNOLOGY (HUNAN) CO LTD
Priority date: 2020-10-28
Filing date: 2020-10-28
Publication date: 2021-11-02
Anticipated expiration: 2040-10-28
Also published as: CN112292021A

Abstract

The invention discloses a method for improving the inserting and welding precision of a PCB antenna, which comprises the following steps: s1, manufacturing a special tray, and fixing the PCB on the special tray; s2, automatically inserting the antenna through an SMT chip mounter, and inserting the antenna into a mounting hole in the PCB; s3, manufacturing a cover plate device to cover the antenna, and limiting the angle of the antenna to ensure that the inclination angle of the antenna on the PCB meets the requirement of 0 +/-5 degrees; and S4, welding the antenna through the selective wave crest. The antenna adopts the novel process of SMT automatic insertion and selective wave soldering, can be flexibly applied to through hole insertion components needing insertion on other types of PCBs, not only can greatly improve the SMT production efficiency, but also can furthest reduce poor tin content in a soldering cavity and ensure very stable soldering quality, and has the advantages of high production efficiency, cost saving and high soldering quality.

Description

Method for improving insertion and welding precision of PCB (printed circuit board) antenna

Technical Field

The invention mainly relates to the technical field of PCB boards, in particular to a method for improving the inserting and welding precision of PCB board antennas.

Background

For the insertion and welding process of the through hole insertion component antenna, the original process flow is as follows: printed Circuit Board (PCB) front and back adhesive plates → PCB front and back pads Printed solder paste → manual insertion antenna → antenna reflow soldering. Because PCB antenna pad position needs two-sided printing tin cream, and the antenna reflow soldering is realized through passing through reflow oven with the antenna behind the manual cartridge antenna again, this kind of printing tin cream reflow soldering technology can have following four kinds of shortcomings:

a. because the antennas are manually inserted, the antennas are required to be placed into the PCB holes one by using tweezers, the efficiency is extremely low, in order to balance the production cycle of the whole production line, a plurality of operators are required to be arranged for inserting the antennas simultaneously to ensure the smooth production of the whole production line, the labor cost is high, and the production efficiency is low;

b. tweezers easily touch an IC and other elements which do not pass through a furnace in the insertion process of the antenna, so that IC deviation or internal bridging and IC omission are caused, and the defective welding proportion generated after the furnace is about 1% (because the defective IC welding repair yield is extremely low and the risk of poor function is increased, the generated defective products can only be scrapped);

c. because the antennas are all manually inserted, although the antennas are perpendicular to the PCB surface before passing through the furnace after the antennas are inserted, the center of gravity of the antennas is not on a bonding pad, 100% of elements after passing through the furnace incline to a certain angle towards the IC direction, the included angle between the PCBA surface and the top of the antennas after the antennas are welded finally has 0 +/-5-degree angle control, about 1% of antenna angle inclination generated after the furnace exceeds the standard of 0 +/-5 degrees, and because the antennas cannot be repaired after reflow welding, only 1% of defective products can be scrapped;

d. through a reflow soldering process of printing solder paste on two sides and manually inserting an antenna to pass through a reflow oven, 100% of cavities can be generated in holes through slicing analysis, wherein the area of the cavities in the antenna holes with 8% of proportion exceeds 25% of the soldering surface and is tin-poor, and the poor tin-poor antenna holes with 8% of proportion cannot be repaired and can only be scrapped.

Disclosure of Invention

In view of the above, the present invention provides a method for improving the insertion and welding precision of a PCB antenna, which can solve the problems of high labor cost, low production efficiency and more defective scrap in the prior art.

The invention discloses a method for improving the inserting and welding precision of a PCB antenna, which comprises the following steps:

s1, manufacturing a special tray, and fixing the PCB on the special tray;

s2, automatically inserting the antenna through an SMT chip mounter, and inserting the antenna into a mounting hole in the PCB;

s3, manufacturing a cover plate device to cover the antenna, and limiting the angle of the antenna to ensure that the inclination angle of the antenna on the PCB meets the requirement of 0 +/-5 degrees;

and S4, welding the antenna through the selective wave crest.

Furthermore, the special tray is of a square structure, a plurality of antenna milling grooves and first positioning holes are formed in the upper surface of the special tray, positioning pins are arranged on each first positioning hole, and the avoiding precision of the positioning pins and the antenna milling grooves is controlled within the range of +/-0.03 mm.

Further, a plurality of first locating hole sets up respectively in upside, downside and the right side of special tray upper surface, just the left and right sides of special tray upper surface all still is provided with the buckle that is used for fixed PCB board.

Further, the cover plate device comprises a first cover plate and a second cover plate, and the first cover plate and the second cover plate are respectively provided with a cover plate milling groove and a second positioning hole corresponding to the antenna milling groove and the first positioning hole on the special tray.

Further, the step S3 specifically includes the following steps:

s31, after the antenna is automatically inserted, the first cover plate is positioned on the PCB and the special tray through the second positioning hole on the first cover plate;

s32, fixing the first cover plate on the special tray through a plurality of positioning pins on the upper surface of the special tray, and correcting the inclination angle of the antenna;

s33, the second positioning hole on the second cover plate penetrates through the positioning pin to press the top of the antenna to ensure the vertical state of the antenna again, and all the inclined antennas meet the requirement of 0 +/-5 degrees after being limited by the first cover plate and the second cover plate.

Furthermore, the thickness of the first cover plate is 0.15mm, the thickness of the second cover plate is 0.05mm, and the precision of the cover plate milling grooves and the second positioning holes formed in the first cover plate and the second cover plate needs to be controlled within the range of +/-0.03 mm.

Further, the key parameters for performing the soldering by selective wave in the step S4 include the moving speed of the nozzle in the XY direction and the wave soldering height of the nozzle.

Further, the moving speed of the spray head along the XY direction is 16-20mm/s, and the wave soldering height of the spray head is 93-97% of the wave height.

Further, the key parameters of the soldering by the selective wave crest in the step S4 further include flux spraying amount, PCBA product preheating temperature, PCBA product preheating time, and solder pot temperature setting, wherein the flux spraying amount is 70-80%, the PCBA product preheating temperature is 80-100 ℃, the PCBA product preheating time is 30sec, and the solder pot temperature is set to 300-.

According to the method for improving the insertion and welding precision of the PCB antenna, the antenna adopts a novel process of SMT automatic insertion and selective wave soldering, can be flexibly applied to through hole insertion components needing insertion on other types of PCBs, not only can the SMT production efficiency be greatly improved, but also poor soldering of a soldering cavity can be reduced to the maximum extent, and very stable welding quality is ensured.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a flow chart of a method for improving the accuracy of inserting and welding a PCB antenna according to the present invention;

FIG. 2 is a schematic structural view of a specialized tray;

FIG. 3 is a schematic view of a PCB positioned on a dedicated tray;

FIG. 4 is a schematic structural view of the first cover plate;

fig. 5 is a schematic structural view of the second cover plate.

Description of reference numerals:

special tray-1 antenna milling groove-2

Locating pin-3 fastener-4

PCB board-5 first cover board-6

Second cover plate-7

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In the present invention, the orientations such as "left", "right", "up" and "down" are used with reference to the view shown in fig. 2. The terms "first" and "second" are used primarily to distinguish one element from another, but do not limit the elements specifically.

Fig. 1 is a flowchart illustrating a method for improving the accuracy of inserting and welding a PCB antenna according to the present invention. As shown in fig. 1 and 5, a method for improving the accuracy of PCB antenna insertion and welding includes the following steps:

s1, manufacturing the special tray 1, and fixing the PCB 5 on the special tray 1;

specifically, referring to fig. 2 and 3, the upper surface of the special tray 1 is provided with a plurality of antenna milling grooves 2, first positioning holes and fasteners 4, each first positioning hole is provided with a positioning pin 3, the precision of the positioning of the PCB board 5 is directly influenced by the precision of the special tray 1, and the precision of the positioning of the PCB board 5 further influences the precision of the antenna insertion, so that the avoiding precision of the positioning pins 3 and the antenna milling grooves 2 is controlled within a range of ± 0.03mm, and the fasteners 4 are used for further fastening the special tray 1 and the PCB board 5. Preferably, the first positioning holes are respectively formed at the upper side, the lower side and the right side of the upper surface of the special tray 1, and the fasteners 4 are respectively formed at the left side and the right side of the upper surface of the special tray 1. In the embodiment shown in fig. 2, three first positioning holes and three positioning pins 3 are arranged on the upper side and the lower side of the upper surface of the tray, two first positioning holes and two positioning pins 3 are arranged on the right side of the upper surface of the tray, and meanwhile, one buckle 4 is arranged on the right side of the upper surface of the tray, and two buckles 4 are arranged on the left side of the upper surface of the tray.

S2, automatically inserting the antenna through an SMT (Surface Mount Technology) chip mounter, and inserting the antenna into a mounting hole on the PCB 5; because the identification verification of the component identification mode, only the composite identification mode of REF 241(REF 241 is one of the codes in the identification mode and represents the composite identification mode) is the most stable, the higher the component repeatability identification precision is, the more favorable the antenna automatic insertion is, and the steps are specifically represented as follows:

s11, carrying out repeated identification precision detection on the antenna through a composite identification mode of REF 241, wherein the identification precision is controlled within 0.02 mm;

s12, adding a cursor point beside each antenna of each block on the PCB 5 as a unique identification point to solve the insertion problem caused by the position deviation during feeding, such as the problem of antenna insertion tilting or omission;

s13, sucking the identified antenna through a suction nozzle of the SMT chip mounter, and inserting the antenna into a mounting hole formed in the PCB 5, wherein the inserting depth is 0.9mm, and the sucking height is 0.4 mm. It should be noted that, the above-mentioned suction height refers to a gap height of 0.4mm that needs to be reserved on the surface of the suction antenna of the SMT pick-up nozzle.

S3, manufacturing a cover plate device to cover the antenna, and limiting the angle of the antenna to ensure that the inclination angle of the antenna on the PCB 5 meets the requirement of 0 +/-5 degrees; specifically, the cover plate device comprises a first cover plate 6 and a second cover plate 7, wherein the first cover plate 6 and the second cover plate 7 are respectively provided with a cover plate milling groove and a second positioning hole corresponding to the antenna milling groove 2 and the first positioning hole on the special tray 1, the thickness of the first cover plate 6 is preferably 0.15mm, the thickness of the second cover plate 7 is preferably 0.05mm, and the precision of the cover plate milling groove and the second positioning hole arranged on the first cover plate 6 and the second cover plate 7 is required to be controlled within a range of +/-0.03 mm, which is specifically shown in fig. 4 and 5;

the step S3 can be specifically decomposed into the following processes:

s31, after the antenna is automatically inserted, the first cover plate 6 is positioned on the PCB 5 and the special tray 1 through a second positioning hole on the first cover plate;

s32, fixing the first cover plate 6 on the special tray 1 through a plurality of positioning pins 3 on the upper surface of the special tray 1, and correcting the inclination angle of the antenna;

s33, a second positioning hole on the second cover plate 7 penetrates through the positioning pin 3 to press the top of the antenna to ensure the vertical state of the antenna again, and all the inclined antennas meet the requirement of 0 +/-5 degrees after being limited by the first cover plate 6 and the second cover plate 7.

And S4, welding the antenna through the selective wave crest. The key parameters OF the antenna selective wave soldering comprise the moving speed OF the spray head along the XY direction, the wave soldering height OF the spray head, the spraying amount OF the soldering flux, the preheating temperature OF a PCBA (Printed Circuit Board Assembly), the preheating time OF a PCBA product and the temperature setting OF a tin furnace, wherein the PCB blank Board passes through an SMT upper part or the whole process OF a DIP plug-in, the PCBA product is short for PCBA), the relevant parameters OF the spraying amount OF the soldering flux, the preheating temperature and time OF the PCBA product and the set parameters OF the temperature OF the tin furnace do not directly influence the quality OF the antenna wave soldering, therefore, the parameters are not used as the key parameters verified by DOE (DESIGN OF experimenter), but the moving speed OF the spray head along the XY direction and the wave soldering height OF the spray head during the selective wave soldering directly influence the quality OF the antenna wave soldering, preferably, the moving speed OF the spray head along the XY direction is 16-20mm/s, the height of the spray head wave-soldering is 93-97% of the height of the wave, and it should be noted that the value of the height of the wave is generally 5mm, and the height of the spray head wave-soldering is 4.65 mm-4.85 mm. Therefore, these two parameters are considered to be verified in the DOE as key parameters. The relevant test verification is carried out by selecting the parameter values as follows:

table-antenna selective wave soldering key parameter value

Setting plans of different combination parameters of the DOE test matrix:

related parameters of soldering flux spraying and PCBA product preheating and parameters of tin furnace temperature setting are selected from all combinations, the set values of all the combinations are selected, the selective wave soldering parameters are selected, the moving speed of a spray head in the XY direction and the upper limit and the lower limit of the wave soldering height of the spray head are combined into four different combinations, namely, I, II, III and IV, and the specific table is II:

key parameter value combination for selective wave soldering of two antennae

Different combinations of wave soldering verification plans:

the total quantity of one connecting piece of the product is set to be 90pcs, the total quantity of two connecting pieces for wave soldering of each combination is 180pcs, and through the parameter combination, the visual inspection result of the wave soldering appearance is shown in the following table III:

table for visual inspection results of three appearances

Combination of	I	II	III	IV
					Visual inspection of the number of visual inspection	180	180	180	180
Number of failures	0	0	0	0
					Percent of pass	100％	100％	100％	100％
Reception standard	99％	99％	99％	99％
					Pass/Fail	Pass	Pass	Pass	Pass

The quality testing personnel of the test product inspects the test product according to ICS IS-ase-101 and Ver.A0 standards, the antenna after wave soldering has no bad defects such as bridging, little tin, tilting, omission and the like, and the qualification rate of the four combined visual inspection results IS 100%.

And (3) measuring the inclination angle of the antenna: the angle measurement IS carried out by quality testing personnel according to the ICS IS-ase-101 and Ver.A0 standard, 5pcs are selected from each combination to measure the antenna angle (20 pcs in total), and all data of the angle measurement result are considered to be qualified within the range of 0 degrees +/-5 degrees. The tilt angle measurement data of each group of antennas is as follows:

meter four-antenna inclination angle measurement data meter

Combination of	I	II	III	IV
					Number of X-ray tests	180	180	180	180
Number of failures	0	0	0	0
					Percent of pass	100％	100％	100％	100％
Reception standard	99％	99％	99％	99％
					Pass/Fail	Pass	Pass	Pass	Pass

As can be seen from the above table, the four combined measuring antenna angles all meet the requirement of 0 +/-5 deg.

X-ray test results: and (4) inspecting the product by a quality inspector according to the ICS IS-ase-101 and Ver.A0 standard, and inspecting whether the product can generate adverse effects on elements such as other ICs (integrated circuits) after wave soldering, such as defects of IC bridging, tin shortage, tilting, omission and the like, wherein the qualification rate of the X-ray inspection result IS more than 99% and the product IS qualified. The X-ray inspection qualification rate data is as follows:

meter five-antenna inclination angle measurement data meter

As can be seen from the table above, the qualification rates of the four combined X-ray tests are all 100%.

And (4) analyzing the electrical measurement result: and (4) testing the product to be tested by quality testing personnel according to the ICS IS-ase-101 and Ver.A0 standards, wherein the electrical testing qualified rate IS more than 99 percent and IS regarded as qualified. The electrical measurement yield data are as follows:

meter six-antenna inclination angle measurement data meter

Combination of	I	II	III	IV
					Measuring quantity electrically	180	180	180	180
Number of failures	0	0	0	0
					Percent of pass	100％	100％	100％	100％
Reception standard	99％	99％	99％	99％
					Pass/Fail	Pass	Pass	Pass	Pass

As can be seen from the table, the qualification rates of the four combined electrical measurement results are all 100%.

Antenna slice analysis: the method needs to slice and analyze the tin-coating condition of the pin of the antenna in the hole 5 of the PCB, and whether bubbles or welding holes exist in the hole or not causes that the tin-coating quantity of the pin of the antenna is less than 75 percent and the tin is less. And selecting 1pcs product in each combination to carry out slicing analysis on the antenna, wherein the slicing analysis result shows that no hole exists in the antenna holes of the four combinations, and the filling amount of soldering tin in the holes is 100%.

Thus, conclusion by DOE test: all parameters are verified and the test results are all qualified, and after the antenna selective wave soldering, all the test results are qualified whether from antenna appearance soldering, antenna angle measurement, X-ray inspection, ET test or antenna slice analysis. The preferred embodiment of the key parameters of selective wave soldering thus derived is as follows: the spraying amount of the soldering flux is 70-80%, the preheating temperature of the PCBA product is 80-100 ℃, the preheating time of the PCBA product is 30sec, and the temperature of the tin furnace is set to be 300℃ and 320 DEG C

In summary, compared with the prior art, the invention has the following characteristics and advantages:

a. because the antenna realizes that the SMT chip mounter automatically inserts and replaces manual hand swing, the UPH (Unit Per Hour, yield Per Hour) of one chip mounter is equivalent to the UPH of a plurality of operators simultaneously hand swing antenna, the SMT production efficiency is greatly improved, and the manpower is saved;

b. the automatic insertion of the antenna can not cause the problems of IC and other elements offset, less tin and the like in the manual swinging process of the antenna, and the poor scrap caused by human factors is completely avoided;

c. after the antenna is automatically inserted, the antenna is limited through a special cover plate device, the inclination angle of the antenna before wave soldering is controlled within a standard range of 0 +/-5 degrees, and the poor scrapping that the inclination angle of the antenna exceeds the standard due to manual swinging is completely avoided;

d. the antenna welded by adopting the selective wave soldering process can not generate a cavity in a hole after being sliced and analyzed, the filling amount of soldering tin in the hole 5 of the PCB basically reaches 100 percent, and compared with a reflow soldering process, poor scrapping of less tin is completely avoided, and the soldering quality of a pin of the antenna is greatly improved.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A method for improving the inserting and welding precision of a PCB antenna is characterized by comprising the following steps:

s1, manufacturing a special tray, and fixing the PCB on the special tray, wherein the special tray is of a square structure, the upper surface of the special tray is provided with a plurality of antenna milling grooves and first positioning holes, each first positioning hole is provided with a positioning pin, and the avoidance accuracy of the positioning pins and the antenna milling grooves is controlled within the range of +/-0.03 mm;

and S4, welding the antenna through the selective wave crest.

2. The method for improving the inserting and welding precision of the PCB antenna as claimed in claim 1, wherein the first positioning holes are respectively disposed at the upper side, the lower side and the right side of the upper surface of the special tray, and the left and right sides of the upper surface of the special tray are respectively provided with a fastener for fixing the PCB.

3. The method for improving the inserting and welding precision of the PCB antenna as claimed in claim 2, wherein the cover plate device comprises a first cover plate and a second cover plate, and the first cover plate and the second cover plate are respectively provided with a cover plate milling groove and a second positioning hole corresponding to the antenna milling groove and the first positioning hole on the special tray.

4. The method for improving the inserting and welding accuracy of the PCB antenna according to claim 3, wherein the step S3 specifically comprises the following steps:

5. The method for improving the inserting and welding precision of the PCB antenna according to claim 4, wherein the thickness of the first cover plate is 0.15mm, the thickness of the second cover plate is 0.05mm, and the precision of the cover plate milling grooves and the second positioning holes formed in the first cover plate and the second cover plate is controlled within the range of +/-0.03 mm.

6. The method for improving the mounting and soldering accuracy of the PCB antenna as recited in claim 5, wherein the key parameters for soldering by selective wave soldering in step S4 include the moving speed of the nozzle head in XY directions and the wave soldering height of the nozzle head.

7. The method for improving the inserting and welding precision of the PCB antenna as recited in claim 6, wherein the moving speed of the nozzle head along the XY direction is 16-20mm/s, and the wave soldering height of the nozzle head is 93-97% of the wave height.

8. The method for improving the antenna mounting and soldering accuracy of the PCB as recited in claim 7, wherein the key parameters for soldering by selective wave soldering in step S4 further include flux spraying amount 70-80%, preheating temperature of PCBA product 80-100%, preheating time of PCBA product 30sec, and solder pot temperature setting 300-320 ℃.