1. Solder paste printing ScreenPrinting

1. Printing press

     a. What is the model and basic working principle of the printing press you use?

 

Answer: SP28P-DH working principle: The X-Y Table up and down motor is controlled through program editing, and the Y-pumping Motor drives the air pressure to control the scraper head to scrape back and forth to form a printing PCB process;

     b. What are the basic meanings of each parameter and their impact on printing quality?

 

Answer: 1. MARK data; refers to the specific parameters of the MARK point of the stencil\PCB under the condition of a reference origin; this data is directly related to the printing accuracy and production efficiency;

     c. Type of scraper head (ordinary pressure scraper head, programmable scraper head, rheological pump scraper head...) and characteristics?

 

Answer: Ordinary pressure scraper head: This type is generally controlled by cylinder adjustment, which is convenient for parameter setting and maintenance;

 

Programmable scraper head: This type is controlled by an electrical motor. The cost is high and requires regular and strict maintenance. The parameter setting can be accurate to 0,001;

     d. Details of the printing process and possible defects?

 

Answer: 1. Solder paste environment control during the printing process; the temperature is required to be controlled at 22-24 degrees, and the humidity is preferably controlled at 45%-65%. As the temperature increases, the viscosity of the solder paste decreases, which will cause flying parts, solder paste collapse and other defects. When the temperature decreases, the viscosity increases, which will cause component displacement and tombstones. When the humidity decreases, the solder paste will dry out, resulting in less tin for printing and flying components. When the humidity increases, the solder paste will react chemically, causing solder beads to splash and short circuits. etc. defective;

 

2. Stencil cleaning: Failure to clean the stencil on time will cause short circuits of closely spaced pin components, less tin, tin beads and other defects; 3. Solder paste cleaning: During the printing process, the solder paste must be cleaned on time, failure to clean on time will cause Resulting in poor printing; 4. On-line time control of printed matter: the printed matter must be reflowed within two hours to maintain the soldering effect held by the solder paste; 5. Effective inspection of printed matter: If no effective inspection is performed after PCB printing , will increase the chance of forming defective products;

     e. Defects caused by improper (adequate) PM?

 

Answer: Improper PM will cause the production line to stagnate, affect product shipments, increase the company's costs, and affect efficiency;

     f. PPK practices and improvement measures when capabilities are insufficient?

 

Answer: The method of PPK is to evaluate the small batch production capacity before the product enters mass production. Generally, the PPK value is ≥ 1.67;

 

Improvement measures when capacity is insufficient: During the product evaluation stage, the engineering team conducts predictive analysis of products and equipment to identify problems early, formulate preventive improvement measures, and solve problems to improve production line production capacity;

2. Solder paste

     a. What are the main components of the solder paste you use and what are the functions of each component?

 

Answer: Solder paste composition: 63% leaded tin/37% lead, 96% lead-free tin/3.5% silver/0.5% copper

 

Halide: remove copper surface oxide

 

Organic acid: Activating tin-lead surface\Using FLUX for decontamination at high temperatures

 

Amines: activated silver surface

 

Viscosity modifier (thixotropic agent): printing and molding

 

Solvent: Dissolves cured matter and active agent, needs to be volatile

 

Anti-oxidant: prevent oxidation of tin powder, belongs to phenolics

 

Tackifier: Maintain the stickiness after patching and before REFLOW

     b. Printing characteristics, such as pressure range, speed range...?

 

Answer: Pressure: 15-30㎡\N Speed: 50-120CM\M

     c. What are the main types and causes of defects?

 

Answer: Displacement: 1. Printing displacement; 2. SMT displacement; 3. Improper reflow soldering temperature setting; 4. Caused by human work;

 

Short circuit: 1. Printing short circuit\solder paste thickness is too thick, 2. SMT pressure is too high; 3. Improper reflow soldering temperature setting

     d. Basic usage environment requirements and control methods, such as temperature recovery, humidity...?

 

Answer: The operating environment of the SMT workshop needs to be controlled at a temperature of 22-24 degrees and a humidity of 45%-65%. Auxiliary appliances such as air conditioners, exhaust fans, dehumidifiers, etc. are required. An effective thermometer and hygrometer must be used. A dedicated person will monitor this, and if it exceeds the scope, immediately make a request to the project to improve the environment;

     … …

3. Steel mesh

     a. Manufacturing process and characteristics, laser, electroforming, corrosion step (Step-up)...?

 

Answer: 1. Laser is made by laser cutting method. Its characteristics are: expensive, high cost and long production time. It is more suitable for general fine-pitch IC production process.

 

2. Electroforming is made by laser and etching processes followed by electroplating. Its characteristics are: its production time is long, the cost is high, and the production process is complex. The main feature is good tin removal, and it is mainly used in ultra-fine pitch IC production processes;

 

3. It is made by etching using chemical etching method. Its characteristics are: cheap price, low production cost, fast production time, but it is not easy to use in fine-pitch IC production process;

     b. Hole opening plan for general components?

 

Answer: The general component opening scheme generally opens at a ratio of 1:0.95;

     c. Hole opening plan for special components, anti-tin ball treatment, reflow of through-hole parts...?

 

Answer: The general opening ratio for anti-tin bead production is 1:0.95, and the opening is crescent-shaped or concave; the general opening ratio for through-hole reflow process is 1:1.5;

     d. Use special software to generate stencil files?

 

Answer: POWERPCB generation

     e. Common defects caused and their solutions?

 

Answer: Common defects caused by stencils include: less tin in printing (difficulty in tin removal), sharpening, short circuit, insufficient tin in extra large pads, and poor soldering. Solutions: less tin (difficulty in tin removal) and sharpening: the stencil can be Surface polishing treatment; short circuit: the proportion of the opening can be appropriately reduced; extra large pads with less tin and empty soldering: the opening can be appropriately expanded at a safe distance;

     f. Cleaning methods and effects?

 

Answer: Method: manual cleaning; ultrasonic cleaning;

 

Manual cleaning, the surface is easy to clean, but the steel mesh wall is difficult to clean;

 

Ultrasonic cleaning: can ensure the hole wall is clean;

 

 

4.PCB/FPC

     a. PCB/FPC manufacturing process?

 

Answer: File processing---Image--Forming--Wire production--Drilling---Electroplating---Multi-layer PCB lamination--Processing of solder mask, screen printing surface, gold finger plating---Testing

     b. What are the characteristics of HASL/OSP/gold plating?

 

Answer: HASL surface tin plating: high price. PCB has long storage time and good tin application performance; OSP surface treatment anti-oxidation film: cheap, not easy to store for a long time and easy to tin application; gold plating surface gold plating: strong conductivity, expensive price and suitable for high-end product

     c. What are the general requirements for pad and layout design?

 

Answer: General requirements for PAD layout design: 1. PAD conductor width parameter Min 0.18mm; 2. PAD conductor spacing Min 0.2mm; 3. PAD conductor distance from the board edge parameter Min 0.3mm; 4. PAD conductor distance from the punching edge Min 0.3mm ;5. Line printing dimensional accuracy deviation parameter ±0.1mm;

     … …

2. High Speed ChipShooter

1. SMT machine

     a. What type of placement machine are you using and its basic working principle?

 

Answer: Model: MSR-150 Basic working principle: This placement machine is a turret type and uses 16 placement heads to perform picking, imaging, angle conversion and correction, placement, discarding, NOZZLE replacement, return to the origin, and repeated actions. The components are supplied back and forth through the Z pumping box to perform the entire patching action;

     b. What are the various aspects of the PVP (Pick-Vision-Placement) process and possible defects?

 

Answer: Defects easily caused by Pick-Linsensor--Vision-Angle Conversion--Placement process links: Pick-up, identification, and placement links: will lead to displacement, missing parts, flipped parts, solder beads, short circuits and other defects;

     c. Defects caused by improper PM?

 

Answer: Improper PM will cause the production line to stagnate, affect product shipments, increase the company's costs, and affect efficiency;

     d. What are the PPK practices and measures to be taken when process capabilities are insufficient?

 

Answer: The method of PPK is to evaluate the small batch production capacity before the product enters mass production. Generally, the PPK value is ≥ 1.67; improvement measures when the capacity is insufficient: during the product evaluation stage, the engineering team will conduct a predictive analysis of the product and equipment. Detect problems early, formulate preventive and improvement measures, and solve problems to improve production line production capacity;

2. Placement procedure

     a. How to generate a patch program?

 

Answer: You can use the coordinate file provided by the customer and use the special programming software for the placement machine for programming; if the customer does not provide the coordinate file, you can use the PCB format file to generate the coordinates using POWERPCB software, and then use the special software to edit;

 

    b. Management of placement procedures?

 

Answer: The program management specifications are formulated internally by the project, a program team is set up to professionally produce the program, and the program engineer professionally manages the storage;

     c. How to prevent incorrect materials?

 

Answer: Material preparation can be carried out. IPQC will first conduct an inspection and verification, and then conduct another verification when loading materials, and sign for confirmation. Then the first board produced will be checked again and finally passed after it is OK;

     e. What are the basic requirements for component databases?

 

Answer: The basic requirements are: material size; machine photographic identification method; NOZZLE selection; camera selection; FEEDER selection;

3. General use SurfaceMounter

SMT machine

1. a. What type of placement machine are you using and its basic working principle?

 

Answer: Model: MPAG3; The basic working principle is: This equipment is a wall-mounted placement machine. It uses X--Y motors to move the placement head back and forth. TABLE uses Z-axis motors to move up and down to fix the PCB, and then through editing program to carry out the entire placement process;

     b. Various aspects and possibilities of the PVP (Pick-Vision-Placement) process

 

Answer: Defects easily caused by Pick-Linsensor--Vision-Angle Conversion--Placement process links: Pick-up, identification, and placement links: will lead to displacement, missing parts, flipped parts, solder beads, short circuits and other defects;

     d. What are the PPK practices and measures to be taken when process capabilities are insufficient?

 

Answer: The method of PPK is to evaluate the small batch production capacity before the product enters mass production. Generally, the PPK value is ≥ 1.67; improvement measures when the capacity is insufficient: during the product evaluation stage, the engineering team will conduct a predictive analysis of the product and equipment. Detect problems early, formulate preventive and improvement measures, and solve problems to improve production line production capacity;

     f. Special nozzle design?

 

Answer: In case of special components, NOZZLE can be processed or specially made, such as enlarging or lengthening NOZZLE, etc.;

2. Placement procedure

     a. How to generate a patch program?

 

Answer: You can use the coordinate file provided by the customer and use the special programming software for the placement machine for programming; if the customer does not provide the coordinate file, you can use the PCB format file to use the POWERPCB software to generate the coordinates, and then use the special software to edit;

 

 

     b. Management of placement procedures?

 

Answer: The program management specifications are formulated internally by the project, a program team is set up to professionally produce the program, and the program engineer professionally manages the storage;

     c. How to prevent incorrect materials?

 

Answer: Material preparation can be carried out. IPQC will first conduct an inspection and verification, and then conduct another verification when loading materials, and sign for confirmation. Then, the first board produced will be checked again and finally passed after it is OK;

     e. What are the basic requirements for component databases?

 

Answer: The basic requirements are: material size; machine identification method; NOZZLE selection; camera selection; FEEDER selection

     f. What are the requirements for Nozzle and Feeder for special components?

 

Answer: Special components require the suction surface size of the nozzle, the suction vacuum value, and the size of the nozzle for Nozzle; the requirements for the Feeder include: the spacing of the tape and reel packaging, the width of the material tape, and the stepping accuracy of the Feeder;

4. (Selective) WaveSolder

(Selective) wave soldering equipment

1. a. What type of (selective) wave soldering equipment do you use and its basic working principle?

 

Answer: Basic working principle: First, there is a preheating stage using high-power heating tubes to generate heat. The hot air motor evenly disperses the hot air in the preheating area to carry out the entire preheating stage. The solder is melted in the welding area, and then the pneumatic device The solder forms wave peaks to carry out the soldering process of PCBA;

     b. Defects caused by improper PM?

 

Answer: Improper PM will cause the production line to stagnate, affect product shipments, increase the company's costs, and affect efficiency;

     c. What is the function, principle and setting of preheating?

 

Answer: The function is to equalize the temperature of components of different sizes on the entire PCBA and the PCB, so as to reduce the temperature difference and reach the soldering temperature;

     d. Design of special fixture (nozzle)?

     f. What are the meanings and settings of parameters?

 

Answer: Parameter meaning: It is the necessary data setting to meet the required requirements for the normal operation of the equipment; parameter settings usually need to meet the requirements of the following stages: product preheating (time, temperature) --- welding (time, temperature) )---Cooling (forced cooling)

2. Solder/Flux

     a. What is the alloy composition of solder?

 

Answer: Common ones are: 1.SN99.3%CU0.7%; 2.Sn96Ag3.5Cu0.5

     b. What are the composition and characteristics of flux?

 

Answer: The flux component is mainly synthesized from rosin resin composed of rosin, resin, halide-containing activators, additives and organic solvents; its main characteristics are good solderability and low cost, but high residue after welding and odor. ,volatile;

     c. What is the role of flux?

 

Answer: 1. It can remove the oxides or other surface film layers formed on the surface of the welding components as well as the oxides formed on the surface of the solder itself, so as to achieve the purpose of tinning and soldering firmly on the surface of the soldered object; 2. At the same time, it can Protect the metal surface from being oxidized in the high temperature environment of soldering. 3. Reduce the surface tension of molten tin and promote the dispersion and flow of solder.

5. Reflow Solder

1. Reflow soldering equipment

     a. What type of reflow soldering equipment are you using and its basic working principle?

 

Answer: Model: SAI-838; The basic working principle is: the heating pipe generates heat, and the hot air motor blows the hot air to the reflow soldering vent to form hot air, which is controlled by the programmable system.

     b. Defects caused by improper PM?

 

Answer: Improper PM will cause the production line to stagnate, affect product shipments, and causeThe company's costs will increase and its benefits will be affected;

     c. The length, principle and settings of each heating zone?

 

Answer: The length of each heating zone is 350MM. The principle is: the heating pipe generates heat, and the hot air motor blows the hot air to the reflow soldering vent to form hot air welding; Settings: It varies according to different products. The common main parameter is the temperature zone temperature setting. Fixed, hot air motor speed setting, chain running speed setting, cooling fan speed setting;

2. Reflow curve

     a. What is the recommended reflow profile for the solder paste you are using?

 

Answer: The curve provided by the solder paste supplier is a "tent" type temperature curve;

     b. What are the functions of each stage of the reflow curve?

 

Answer: The heating stage: also called the preheating zone, from room temperature to 120 degrees, is used to raise the PCBA from the ambient temperature to the required activity temperature; the heating slope cannot exceed 4 degrees/s; heating up too fast will cause component damage. If it is too slow, the solder paste will over-heat and will not have enough time to reach the active temperature; usually the time is controlled at about 60S;

 

Constant temperature stage: also called active zone or wet zone, used to raise PCBA from the active temperature to the required reflow temperature; first, it allows components of different qualities to be homogeneous in temperature; second, it allows flux to be activated and the solder paste to volatilize The common solder paste active temperature is 120-150 degrees, the time is between 60-120S, and the temperature rise slope is generally controlled at about 1 degree/S; all components on the PCBA must reach the tin melting process. Different The melting points of solder pastes with metal components are different. The melting point of lead-free solder paste (SN96/AG3.5/CU0.5) is generally 217-220 degrees, and the melting point of lead-containing solder paste (SN63/PB37) is generally 183 degrees. The melting point of silver-containing solder paste (SN62/PB36/AG2 ) is 179 degrees;

 

Reflow stage: also called the peak zone or the final heating zone, this zone raises the solder paste from the active temperature to the recommended peak temperature, and heats the process from molten tin to liquid state; the active temperature is always lower than the melting point, and the peak temperature is always lower than the melting point. Above the melting point, the typical peak temperature range is (SN63/PB37) from 205-230 degrees; lead-free (SN96/AG3.5/CU0.5) from 235-250 degrees; setting this temperature too high will cause The temperature rise slope exceeds 2-5 degrees/S, or reaches a value higher than the recommended peak value. This situation will cause PCB delamination, curling, component damage, etc.; Peak temperature: the highest temperature reached by PCBA during the welding process;

 

Cooling stage: The ideal cooling curve is generally a mirror image of the reflow curve. The closer the mirror image relationship is, the tighter the solid structure of the solder joints, the higher the quality of the solder joints, and the better the bonding integrity. Generally, the cooling slope is controlled at 4 degrees. /S;

 

 

   c. Are you familiar with the reflow curve measurement software?

 

Answer: 1.SAI-838; 2.KIC-2000

     d. What are the types and working principles of thermocouples?

 

Answer: Type: T-TYPE-; Working principle: Use a high-temperature-resistant special test wire (divided into positive and negative electrodes) to spot-weld the two wires at one end with a welder to make them conductive, and then connect the positive and negative electrodes respectively. The positive and negative electrodes of the thermocouple are finally connected to the temperature tester, and the temperature is sensed through the thermocouple to obtain the temperature and store it;

     e. What are the specific requirements for reflow time, peak temperature and holding time?

 

Answer: Reflow time requirements: It mainly varies according to the product. Generally, the reflow time requirements are in the range of 40-60; the peak temperature requirements are generally (SN63/PB37) 205-230 degrees, lead-free (SN96/AG3.5/CU0.5) 235-250 degrees; constant temperature time requirements: This stage varies according to different solders, generally 60-120S is the standard;

     f. Common defects and solutions?

 

Answer: Air soldering: 1. Increase the constant temperature time and temperature appropriately; 2. Increase the reflow time;

 

Tombstone: Reduce the temperature climbing slope, increase the constant temperature time, and reduce the temperature difference of components on the PCB;

 

Tin beads: Reduce the temperature climb slope and make the temperature climb smooth;

6. Visual Inspection & Failure Analysis

     a. Understand the inspection standards of related products, such as IPC-A-610C?

 

Answer: IPC-A-610D Acceptability of Electronic Components

 

IPC-A-600G circuit board quality acceptance specifications

 

IPC-7711/7721 Rework and Repair of Electronic Components

 

IPC-J-STD-004 Flux requirements for soldering

     b. What are the special requirements for your products, such as aviation products?

 

Answer: The special requirements for aerospace products are: 1. The PCB is required to be made strictly, with excellent conductivity, and the production process is gold-plated. 2. The product appearance is required to be high, and there must be no bad appearance. 2. Rejection of repair products; 3. Static electricity is required. Strict protection;

   

 

  c. How does the inspection equipment work, such as AOI?

 

Answer: The working principle of AOI: First, the host computer edits the program. The machine is equipped with various component libraries, which can perform imaging and editing of various components. Then, the camera uses three-color light scanning and imaging to identify the system to check and determine whether there are any bad problems in the PCBA;

 

 

     d. What is the normal image of the component under X-Ray?

 

Answer: The normal image of the component under X-RAY is black;

     e. Slice analysis, scanning electron microscope weighing analysis, red ink test, drop test, vibration test...

7. Other processes

     a. Understand the use and simple control of PLC and basic accessories of the production line?

     b. What are the settings related to the principle of the cutting machine?

     c. ESD, EHS

 

Answer: ESD is electrostatic discharge; EHS is environmental health and safety;

8. Interface with other departments and other basic knowledge

     a. Understand product design, basic processes and requirements for introduction?

     b. Output setting?

 

Production time per hour ÷ per large board × number of impositions × percentage of abnormality = output

     c. What are the basic procedures and requirements for equipment introduction and evaluation?

 

Answer: First, understand the usage of relevant equipment in the industry, investigate the product market, select products that are more suitable for the company, then conduct a trial evaluation of the equipment, and then submit the opinions or relevant data forms to superiors for approval, and finally the relevant departments will make the purchase;

     d. Basic quality control, QC 7 Tools,

 

1. Characteristic factor diagram

 

2. Checklist

 

3. Plato

 

4. Histogram

 

5. Layer classification method

 

6. Scatter plot

 

7. Control chart

 

e. Six Sigma

 

Answer: sorting, rectifying, sweeping, cleaning, literacy, safety;