Shielding Methods In High Speed ​​PCB Design

The transmission rate of high-speed PCB design and routing system is accelerating with the changes of the times, but which also brings a new challenge to it – The anti-interference ability is getting weaker and weaker. This all stems from the fact that the higher the frequency of information transmission, the more sensitive the signal and the weaker the energy, so the routing system is more and more susceptible to interference. In some common electronic equipment, such as computer screens, mobile phones, motors, radio broadcasting equipment, etc., cables and equipment are able to interfere with other components or be seriously interfered by other interference sources.

Shielding Methods In High Frequency PCB Design

Especially when using high-speed data networks, the time required to intercept a large amount of information is significantly lower than the time required to intercept low-speed data transmissions. The twisted pair in the data twisted pair can resist external interference and inter-pair crosstalk through its own twisting at low frequencies, but at high frequencies (especially when the frequency exceeds 250MHz), the twisting alone cannot achieve anti-interference. Purpose, only shielding can resist external interference.

The cable shield acts like a Faraday shield. Interfering signals enter the shield, but not the conductors. Therefore, the data transfer can operate without problems. Network transmission is blocked because shielded cables have lower radiated emissions than unshielded cables. Shielded networks (shielded cables and components) can significantly reduce the radiation level of electromagnetic energy that may be intercepted as it enters the surrounding environment.

Shielding options for different interference fields mainly include electromagnetic interference and radio frequency interference. Electromagnetic interference (EMI) is mainly low frequency interference. Electric motors, fluorescent lamps, and power lines are common sources of EMI. Radio frequency interference (RFI) refers to radio frequency interference, mainly high frequency interference. Wireless communications such as radio, television broadcasting, and radar are common sources of RF interference. For immunity to EMI, braided shielding is the most effective because of its lower critical resistance; For RFI, foil shielding is the most effective. Since the braided shielding depends on the change of wavelength, the gap generated by the braided shield allows the high-frequency signal to freely enter and exit the conductor; for the mixed interference field of high and low frequencies, the combined shielding method of the foil layer with the broadband coverage function and the braided mesh should be adopted. Generally speaking, the higher the mesh shielding coverage, the better the shielding effect.

Grande’s PCB Design Capabilities

Maximum Signal Design Rate: 10Gbps CML differential signal;
Maximum PCB Layout Layers: 40 layers;
Minimum Line Width: 2.4mil;
Minimum Line Spacing: 2.4mil;
Minimum BGA PIN Spacing: 0.4mm;
Minimum Mechanical Hole Diameter: 6mil;
Minimum Laser Drilling Diameter: 4mil;
Maximum Number of PINs: ;63000+
Maximum Number of Components: 3600;
Maximum Number of BGAs: 48+.

Advantages Grande Circuit Board Assembly

1)Strength Guarantee

▪ SMT factory: With imported SMT machines and multiple optical inspection equipment, which is able to produce 4 million points per day. Each process is equipped with QC personnel who will keep an eye on product quality.

▪ DIP production line: Two wave soldering machines and more than 10 employees who have worked for over three years. That’ s to say, these workers are highly skilled and can weld various SMT & DIP components.

2)Quality Assurance With High Cost Performance

▪ High-end equipment can paste precision special-shaped parts, BGA, QFN, 0201 package. It can also be soldered prototype PCBA via SMT machine and placing bulk materials by hand.

▪ Both samples, small and large batches can be produced. And there is no SMT Machine starting cost.

3)Rich Electronic Products SMT Soldering Experience With Stable Delivery

▪ Accumulated services to thousands of electronics companies, involving SMT soldering services for various types of automotive equipment and industrial control motherboards. Furthermore, PCBA Products are often exported to Europe and the United States, and the quality is able to be affirmed by new and regular customers.

4)Strong Maintenance Ability & Reliable After-Sales Service

▪ The maintenance engineers have sophisticated experience so that those defective boards caused by all kinds of SMT soldering can be repaired. Meanwhile, ensuring the connectivity rate of each circuit board also make sense.

▪Order problems feedback will get response, solution and solved as soon as possible.

Why SMT Assembly Cost May Rise? The 5 Most Frequently Missing Data in PCBA Inquiry

Why SMT Assembly Cost May Rise?

Since the phenomenon of “lack of chips” still exists in 2022, the serious situation of rising transportation cost and high supply chain cost has spread to the entire PCBA contract manufacturing industry, such global situation has hardly left several industries unaffected. This is why we expect SMT Assembly cost continue to rise. Here are some reasons indicates why SMT Assembly cost will increase:

1. The shortage of raw materials

Earlier we analyzed how the global shortage of “chips” affects printed circuit boards (PCBs), and the raw materials of various commodities also directly affect manufacturing costs, and the price of copper in particular is increasing significantly. Therefore, it is very important to take the time to research alternative materials when manufacturing bare PCB. There may be a selection of newer, more readily available materials that can be used in the production process. Since demand will not decrease anytime soon, it is important to plan months or years in advance, especially when supply is already limited. The supply situation will not improve in the short term.

2. The workforce remains a challenge

Labor cost and fees vary based on the geographic location of the business, regardless of industry. The PCBA manufacturing industry is facing labor shortages, which may be another factor affecting future cost. The shortage of front-line workers such as solder workers and DIP plug-in workers is particularly tense. In this industry, quality is paramount, so finding cheap labor substitutes isn’t always a viable option. Hiring inexperienced short-term labor will make PCBA boards more prone to defects and cause problems in the production process, such as delays, downtime or worse. As labor continues to be required to maintain quality at the necessary level, costs may increase as a result.

3. Market demand continues increasing

Demand will continue to rise as more and more products require PCBAs. Due to the shortage of raw materials and labor, the supply capacity of the product will be in a situation of short supply and may cause the end-user cost to rise. It’s just a matter of supply and demand.

However, with the development and promotion of new prevention and control measures, the global unblocking is worth looking forward to, and we expect a certain correction in mid-2022.

The 5 Most Frequently Missing Data In PCBA Inquiry

Most electronic engineering project teams will prepare inquiry files before looking for PCBA manufacturer. In the process of serving all kinds of customers, it is also found that some customers will miss some minor inquiry files details. These details are also important for calculating total cost and time estimates and should be submitted when inquiry. Common omissions are as follows:

1. PCB Solder Mask Details

In addition to clicking yes for the solder mask, there are some basic details to share to the pcba manufacturer. These details include:

1) Solder mask (top, bottom or top and bottom);

2) Solder mask type (LPI-Liquid Light Imaging);

3) Solder mask color (green, blue, black, red, white or transparent);

4) Solder mask surface finish (semi-gloss or matte);

5) Panels coated with solder mask;

2. Surface Finish

The SMT of the surface finish of the PCB affects the quality of solder paste printing. Commonly used surface treatments include Hot Air Solder Leveling (HASL), Electroless Nickel Immersion Gold (ENIG), Electroless Nickel Palladium Immersion Gold (ENEPIG), etc. Therefore, if not specified correctly, the wrong type of surface finish will have a negative impact on the overall PCBA manufacturing efficiency. This is an important detail that is often missed when asking for a quote.

3. Silk Screen Printing

Another often overlooked detail is screen printing. Just like with solder mask, it’s not enough to click “yes” in the silkscreen options. Questions about whether double-sided is required and what color is required should also be answered.

4. Impedance Details

The controlled impedance requirements of the circuit board determine the selection of various parameters. Therefore, if it is not provided, the quotation will be delayed, because the quotation engineer need to judge by guessing or multiple corroboration.

5. Lamination Details

The number of layers, the stacking order, the thickness of each layer, the total thickness of the stack, etc., are all about the details of the stack, which should not be missed.

What’s The Maximum Temperature Resistance of PCB?

In order to ensure the quality of the finished product of the PCB board production process, reliability and adaptability tests are required. The temperature resistance test of the PCB board is to prevent the PCB board from exploding, blistering, delamination and other adverse reactions at excessively high temperatures, resulting in poor product quality or direct scrapping, which is a problem that needs attention. So what is the maximum temperature resistance of the PCB board, and how to do the heat resistance test?

The temperature problem of the PCB board is related to the temperature of its raw materials, solder paste, and surface parts. Usually, the PCB board can withstand a maximum temperature of 300 degrees for 5-10 seconds; The temperature is about 260 for lead-free wave soldering, and about 240 for lead-free wave soldering.

PCB Board Heat Resistance Test

1. First prepare the PCB board production board and tin furnace.
Sampling 10*10cm substrate (or laminated board, finished board) 5pcs; “(Copper-containing substrate without foaming and delamination).
Substrate: 10cycle or more; Laminate: LOW CTE 150 10cycle or more; HTg material 10cycle or more; Normal material 5cycle or more.
Finished board: LOW CTE 150 above 5cycle; HTg material above 5cycle; Normal material above 3cycle.

2. Set the temperature of the tin furnace to 288+/-5 degrees, and use a contact thermometer to measure and correct it.

3. First dip the flux with a soft brush and apply it to the surface of the board, and then use the crucible tongs to take the test board and immerse it in the tin furnace. After 10 seconds, take it out and cool it to room temperature.

4. If there is a problem of bubbling and bursting of the board visually, stop the tin immersion and analyze the initiation point f/m immediately. If there is no problem, continue to cycle until the board bursts, with 20 times as the end point.

5. The blistering area need to be sliced ​​and analyzed to understand the source of the detonation point and take pictures.

The PCB board will have some bad problems at overheating temperature. Therefore, it is necessary to understand the temperature resistance of the PCB board of different materials in detail, and not exceed its maximum limit temperature, so as to avoid the scrap of the PCB board and increase the cost.

Grande PCB Board Production Capacity

Energy production 2 to 14 layers, 14-22 layers can be produced by proofing.
Minimum trace width/spacing: 3mil/3mil BGA spacing: 0.20MM
Minimum aperture of finished product: 0.1mm Size: 610mmX1200mm
Ink: Japan Tamura, Taiyo, Futoken;
FR4: Shengyi, Kingboard, Haigang, Hongren, Guoji, Hazens, South Asia,
(Shengyi S1130/S1141/S1170), Tg130℃/ Tg170℃ Tg180℃ and other high TG plates)
High frequency board: Rogers (Rogers), Taconic, ARLLON;
Surface technology: Spray tin, lead-free spray tin, ENIG, full board gold plating, plug gold plating, full board thick gold, chemical immersion tin (silver), anti-oxidation (OSP) blue glue, carbon oil

Differential Lines Routing Requirements & Operation Skills In PCB Design

The popularity of high-speed serial buses has made more and more differential signals on the PCB. Then, how to perform differential lines in PCB design?

PCB Design Differential Lines Routing Requirements
The impedance requirements of various differential lines are different. According to the PCB design requirements, the differential impedance and the corresponding line width spacing are calculated by the impedance calculation software, and set to the constraint manager. Differential lines are coupled to each other to reduce common-mode interference, and should be routed in parallel as far as possible, and there should be no vias or other signals between the two lines. To reduce the loss, ground vias can be added near the layer-changing holes when the high-speed differential line is changed.

Differential Lines Routing Operation Skills In PCB Design
1. Activate the routing command, select the Route→connect command, and then select the defined differential signal line. At this time, the defined differential line will be pulled out at the same time.
2. Support single-line routing mode. When single-line routing mode is required for local routing, click the right mouse button in the routing command state, and select from the pop-up shortcut menu.
Single Trace Mode command mode.
3. When differential lines routing is placed in a small space, you can switch to Neck Mode. Also, click the right mouse button in the routing command state, and select the Neck Mode command in the pop-up shortcut menu.
4. Select the appropriate differential via pattern in the light of the routing requirements. Click the right mouse button in the routing instruction state, and select the Via Pattern command in the pop-up shortcut menu.

Grande Design Capability
Maximum signal design rate: 10Gbps CML differential signal;
Maximum PCB design layers: 40 layers;
Minimum line width: 2.4mil;
Minimum line spacing: 2.4mil;
Minimum BGA PIN spacing: 0.4mm;
Minimum mechanical hole diameter: 6mil;
Minimum laser drilling diameter: 4mil;
Maximum number of PINs: ;63000+
Maximum number of components: 3600;
Maximum number of BGAs: 48+.

PCB Design Service Process
1. The customer provides schematic to inquiry PCB design;
2. Grande evaluates the quotation according to the schematic and customer PCB design requirements;
3. The customer confirms the quotation, signs the contract, and prepays the project payment;
4. Afrer receiving advance payment, Grande starts to arrange Layout Engineer to layout;
5. Once the layout completed, Grande provides a screenshot of the document to the customer for confirmation;
6. The customer confirms OK, settles the balance, and provides PCB design information.

Why Occur Tin Beads in PCB Assembly?

During assembling PCB, there may be a lot of small issues, such as plating delamination and solder balls. So, why occur tin beads in PCB Assembly?

Reasons Why Occur Tin Beads in PCBA 

1. When the PCB board leaves the liquid solder, it is super easy to form tin beads. This is because when the PCB board and the tin wave are separated, a tin column will be pulled between them. Once the tin column broken and dropped back to the tin cylinder, solder will sputter out, and the solder will fall on the PCB board to form tin beads. Therefore, when designing the tin wave generator and tin cylinder, attention should be paid to reducing the falling height of tin. Small drop height helps reduce dross and spatter.

2. The second reason for the formation of solder balls is the outgassing of volatile substances in the PCB board and solder mask. If there are cracks in the metal layer of the through hole of the PCB board, the volatilized gas of these substances will escape from the cracks after heating, forming tin beads on the component surface of the PCB board.

3. The third cause of solder ball formation is related to flux. Flux can be left under components or between the PCB and the carrier (a tray used for selective soldering). If the flux is not sufficiently preheated and burns out before the PCB touches the tin wave, tin spattering and beading can occur. Therefore, the preheat parameters recommended by the flux supplier should be strictly followed.

This is the reason for the formation of tin beads in PCB Assembly. Apart from that, there are also plenty of other tiny reasons that can cause tin beads. However, with the development of science and technology, technicians have also begun to have rich experience in the production of tin beads. It may be the charm of science and knowledge that it can quickly help technicians find ways to deal with it.

Advantages of car key circuit board assembly

1)Strength Guarantee

▪ SMT factory: With imported SMT machines and multiple optical inspection equipment, which is able to produce 4 million points per day. Each process is equipped with QC personnel who will keep an eye on product quality.

▪ DIP production line: Two wave soldering machines and more than 10 employees who have worked for over three years. That’ s to say, these workers are highly skilled and can weld various SMT & DIP components.

2)Quality Assurance With High Cost Performance

▪ High-end equipment can paste precision special-shaped parts, BGA, QFN, 0201 package. It can also be soldered prototype pcba via SMT machine and placing bulk materials by hand.

▪ Both samples, small and large batches can be produced. And there is no SMT Machine starting cost.

3)Rich Electronic Products SMT Soldering Experience With Stable Delivery

▪ Accumulated services to thousands of electronics companies, involving SMT soldering services for various types of automotive equipment and industrial control motherboards. Furthermore, PCBA products are often exported to Europe and the United States, and the quality is able to be affirmed by new and regular customers.

4)Strong Maintenance Ability & Reliable After-Sales Service

▪ The maintenance engineers have sophisticated experience so that those defective boards caused by all kinds of smt soldering can be repaired. Meanwhile, ensuring the connectivity rate of each circuit board also make sense.

▪Order problems feedback will get response, solution and solved as soon as possible.

The Difference & Connection of Solder Paste, Tin Paste & Flux In SMT Assembly

In the process of SMT Assembly, we will often come into contact with three kinds of pastes, namely solder paste, tin paste and flux paste. The names of the three pastes are similar, but from a professional point of view, they will be quite different.

The Difference & Connection of Solder Paste, Tin Paste & Flux In SMT Assembly

In fact, from a certain point of view, solder paste, tin paste and flux are the same thing, that is, solder paste, but the name is different in Chinese. tBut there are many people who regard solder paste and flux as a product. As a matter of fact, solder paste is paste, whose main component is a paste-like object composed of metal alloy powder.

However, the flux is different, which mainly plays the role of a flux, and its main components are rosin, active agent and solvent. A certain proportion of flux paste will be added to the solder paste during the production process.

The role of tin paste: Alloy powder; To complete the mechanical and electrical connection between electronic components and circuit boards.

The role of solder paste:
1. The carrier of tin powder particles provides suitable rheology and wet strength, which is conducive to the transfer of heat to the soldering area, reduces the surface tension of the solder, and prevents the re-oxidation of the solder and the welding surface during welding.
2. Remove the oxide layer of the soldering surface and tin powder particles, and form a protective layer and a safe residue layer on the surface of the soldering point.
3. The proportion of flux paste can be arbitrarily mixed with various solder powders (tin, silver, copper, bismuth, lead), and can also be mixed with high, medium and low temperature solder powders (100-260) ℃. After being formulated into solder paste, it has the advantages of good solderability, continuous printing and less residue.

To sum up, solder paste, tin paste, and flux actually refer to two products – paste and flux. It is also very simple to distinguish these three. From the appearance color, you can distinguish between the solder paste and tin paste. The solder paste is yellowish, but the tin paste will be gray or black. This is because the component of tin powder is added to the solder paste, and the solder paste is only a pure paste to play a certain role in soldering.

The above is the introduction of the difference and connection of solder paste, tin paste and flux in SMT Assembly.

PCBA Capability

1. Maximum Board: 310mm*410mm(SMT);
2. Maximum Board Thickness: 3mm;
3. Minimum Board Thickness: 0.5mm;
4. Minimum SMD Component: 0201 package or components above 0.6mm*0.3mm;
5. Maximum Weight of Mounted Component: 150 grams;
6. Maximum Component Height: 25mm;
7. Maximum Component Size: 150mm*150mm;
8. Minimum Pin Spacing: 0.3mm;
9. Minimum Spherical Component (BGA) Spacing: 0.3mm;
10. Minimum Spherical Component (BGA) Ball Diameter: 0.3mm;
11. Maximum Component Placement Accuracy (100QFP): 25um@IPC;
12. SMD Capacity: 3-4 million points/day.

Advantages of PCB Assembly In Grande

1. Highly Professional: Grande focuses on PCBA Samples, small and medium batches; For 2 Layer Simple Sample PCBA, Grande promises to deliver within 3-7 working days after the materials are confirmed to be OK.
2. Professional Equipment: Advanced equipment tailored for sample and small and medium batch production, and can be pasted with 0201, BGA spacing 0.3MM, QFN, CSP, CON and other components.
3. Professional Technology: 100% of technical backbones have more than 5 years of work experience, and 85% of front-line operators have more than 3 years of work experience.
4. Grande implements the 5S and 6σ concepts in daily operations, and it is expected that the shipment will be checked at least 7 times.
5. Grande promises that the soldering pass rate is above 99%. If the customer finds soldering defects, the company promises to repair it free of charge.

How To Do BGA Repair For PCBA Board?

There are some bad BGA soldering issues in PCBA board sometimes. If there is a problem with the soldering of a BGA, as a result,  then the whole board will have issue. In this case, BGA repair is required.

Four methods for PCBA processing to do BGA rework

1) Formal Installation Method (Using Ball-Setting Fixture)

1. Place the cleaned and flat BGA pads upwards and place them on the BGA support platform at the bottom of the ball placement fixture.
2. Prepare a small template that matches the BGA pad. The opening size of the template should be 0.05-0.1mm larger than the diameter of the solder ball; The disc is aligned and secured.
3. Place the BGA with the paste flux or solder paste printed on the BGA support platform at the bottom of the ball placement tool, with the printing side facing up.
4. Move the stencil to the top of the BGA (the position that has been aligned in the front), evenly skim the solder balls on the stencil, and shake the ball-setting tool so that there is exactly one solder ball in each leak hole on the surface of the stencil. The solder balls are pulled off the stencil with tweezers.
5. Remove the template.
6. Check whether there is a lack of solder balls on each pad of the BGA device, and fill up the solder balls with tweezers.

2)Manual Placement of Solder Balls

1. Place the BGA chips with the paste-like flux or solder paste printed on the workbench, with the flux-like or solder paste face up.
2. Like the SMT assembly, use tweezers or a suction pen to place the solder balls one by one on the printed paste flux or solder.

3)Directly print an appropriate amount of solder paste and form solder balls through reflow soldering

1. Increase the thickness of the template when SMT is processing the template, and slightly enlarge the opening size of the template.
2. Printing solder paste.
3. Reflow soldering. Solder balls are formed after soldering due to surface tension.

4)Reflow Soldering

Perform reflow soldering as described in the previous section on BGA Repair Process. When soldering, the solder balls of the BGA chips are facing upward, and the amount of hot air is adjusted to the minimum to prevent the solder balls from being blown away. After the reflow soldering process, the solder balls are fixed on the BGA chips. It is carried out in a reflow soldering furnace. The soldering temperature is slightly lower than that of the reflow soldering of the assembly board. After the ball placement process is completed, the BGA chips should be cleaned and mounted and soldered as soon as possible to prevent the solder balls from being oxidized and the device getting damp.

Conclusion

Among the above 4 ball placement methods, the front mounting method (using the ball placement fixture) has the best effect;The flip-chip method (using the ball placement equipment) is the method used for BGA chips packaging, because we purchase the solder balls from the solder paste manufacturer. Poor dimensional accuracy, resulting in some solder balls with small diameters that cannot be activated by paste flux or solder paste; The efficiency of manually placing solder balls is relatively low; Directly printing Shixing solder paste and forming solder by reflow soldering The ball method is the easiest, but this kind of solder ball has poor density and is prone to voids.

Why Occur Tin Beads in PCB Assembly?

During assembling PCB, there may be a lot of small issues, such as plating delamination and solder balls. So, why occur tin beads in PCB Assembly?

Reasons Why Occur Tin Beads in PCBA 

1. When the PCB board leaves the liquid solder, it is super easy to form tin beads. This is because when the PCB board and the tin wave are separated, a tin column will be pulled between them. Once the tin column broken and dropped back to the tin cylinder, solder will sputter out, and the solder will fall on the PCB board to form tin beads. Therefore, when designing the tin wave generator and tin cylinder, attention should be paid to reducing the falling height of tin. Small drop height helps reduce dross and spatter.

2. The second reason for the formation of solder balls is the outgassing of volatile substances in the PCB board and solder mask. If there are cracks in the metal layer of the through hole of the PCB board, the volatilized gas of these substances will escape from the cracks after heating, forming tin beads on the component surface of the PCB board.

3. The third cause of solder ball formation is related to flux. Flux can be left under components or between the PCB and the carrier (a tray used for selective soldering). If the flux is not sufficiently preheated and burns out before the PCB touches the tin wave, tin spattering and beading can occur. Therefore, the preheat parameters recommended by the flux supplier should be strictly followed.

This is the reason for the formation of tin beads in PCB Assembly. Apart from that, there are also plenty of other tiny reasons that can cause tin beads. However, with the development of science and technology, technicians have also begun to have rich experience in the production of tin beads. It may be the charm of science and knowledge that it can quickly help technicians find ways to deal with it.

Advantages of car key circuit board assembly

1)Strength Guarantee

▪ SMT factory: With imported SMT machines and multiple optical inspection equipment, which is able to produce 4 million points per day. Each process is equipped with QC personnel who will keep an eye on product quality.

▪ DIP production line: Two wave soldering machines and more than 10 employees who have worked for over three years. That’ s to say, these workers are highly skilled and can weld various SMT & DIP components.

2)Quality Assurance With High Cost Performance

▪ High-end equipment can paste precision special-shaped parts, BGA, QFN, 0201 package. It can also be soldered prototype pcba via SMT machine and placing bulk materials by hand.

▪ Both samples, small and large batches can be produced. And there is no SMT Machine starting cost.

3)Rich Electronic Products SMT Soldering Experience With Stable Delivery

▪ Accumulated services to thousands of electronics companies, involving SMT soldering services for various types of automotive equipment and industrial control motherboards. Furthermore, PCBA products are often exported to Europe and the United States, and the quality is able to be affirmed by new and regular customers.

4)Strong Maintenance Ability & Reliable After-Sales Service

▪ The maintenance engineers have sophisticated experience so that those defective boards caused by all kinds of smt soldering can be repaired. Meanwhile, ensuring the connectivity rate of each circuit board also make sense.

▪Order problems feedback will get response, solution and solved as soon as possible.

Manual Mounting IC Precautions In PCBA Prototype

In PCB Assembly, some customers only need require and place sample orders, such as only 2-3 pcs sample PCBA. In this case, if the board is not complicated or customer not particularly required, manual soldering usually will be adopted considering saving cost for the customer. The difficulty of Manual Soldering is to mount ICs, especially ICs with high integration.

IC, Integrated Circuit, the industry generally divides its types by IC package form. Traditional ICs include SOP, SOJ, QFP, PLCC, etc., while newer ICs include BGA, CSP, FLIP CHIP, etc. These component types come in various shapes due to the number and size of PINs and the spacing between the pins. The chip component packaging form is a semiconductor device packaging form.

SMT involves a wide variety of components and styles, many of which have formed industry standards, mainly some chip capacitors and resistors; Many are still changing, especially IC, and the changes in packaging forms are endless, making it dizzying.

In the assembly of hand mounting, the difficulty of IC mounting is relatively huge. After all, ICs generally have a large number of pins, which requires our SMT assembly personnel to be patient and operate in strict accordance with the processing requirements to ensure good soldering quality is almost same as machine assembly mounting boards. For instance, due to the high internal integration, it is easy to be damaged by overheating. Generally speaking, the temperature of mounting IC cannot be higher than 200 ℃.

Precautions For Manual Mounting IC

1. The soldering time should be as short as possible, generally no more than 3s.
2. It is best to use an electric soldering iron with a constant temperature of 230 degrees.
3. Anti-static treatment should be done on the SMT Assembly workbench.
4. Choose some sharp and narrow soldering iron tips, and the soldering will not touch the adjacent endpoints.
5. During Manual SMT Assembly, do not remove the preset short lines before soldering the CMOS circuit.
6. Don’t scratch the gold-plated circuit pins with a knife, just use alcohol or a drawing eraser.

The Influence of SMT Lead-Free Process On PCBA rework

The introduction of SMT lead-free Technique has always been a challenge for PCB Assembly for the first time, because if require PCBA repair, it will face more challenges. Performing PCBA repair in a lead-free environment will have higher cost, quality details, time and repeatability issues, and all these issues need pay more attention to.

SMT Lead-Free Technique Requirements:

1. Train operators for lead-free assembly, maintenance and inspection, and evaluate time and cost.

2. Lead-free solder materials are more expensive than traditional solders, such as lead-free wires, welding rods and core solders.

3. The processing temperature (about 30-35°C) of lead-free assembly requires high precision.

4. The lead-free process also requires research and planning of the smt factory to establish the correct PCBA repair process.

Grande believes that the best practice for PCBA repair is to first train and instruct technicians, and develop configuration files based on the characteristics of lead-free processes. Defined rework standards. Regardless of whether standard solder or lead-free solder is required, the process starts in the same way. The steps required are as follows:

1. Define and execute precise thermal profile

2. The failed component must remove

3. Clean up all rust or solder residues on the board and prepare new components

4. Replace components with new solder, flux and reflow soldering

5. Thoroughly check the repair after finished

In a lead-free environment, accurate and reliable rework is more difficult because the PCBA and the components closest to the parts that need to be repaired must withstand multiple high temperature cycles. In order to protect the stability of the circuit board, the preheating temperature should be set not higher than the glass transition temperature of the PCB material.

The next steps involved in the repair process depend on whether there is a lead-free requirement. The difference between standard and lead-free brings many challenges that can only be solved by introducing new or changed processes, including stricter and more precise thermal profiles and extremely high precision throughout the PCBA repair process. This will avoid many costly problems caused by different heat distributions.