Do you know why SMT uses a dust-free workshop

Do you know why SMT uses a dust-free workshop

SMT (Surface Mounted Technology) is a method of installing leadless or short-lead surface mount components (abbreviated as SMC/SMD, known as chip components in Chinese) on the surface of a Printed Circuit Board (PCB) or other substrates. Circuit assembly techniques that are welded and assembled through methods such as reflow soldering or dip soldering.

The production equipment in the SMT workshop is all high-precision machines, and there are certain requirements for the dust-free level of the SMT workshop environment. Excessive dust in the SMT workshop will affect the placement accuracy and soldering quality of tiny components such as 0201 and 01005 with an extremely fine pitch of 0.3mm.

Do you know why SMT uses dust-free workshops? (Figure 2)

Do you know why SMT uses dust-free workshops? (Figure 3)

Excessive dust can also increase equipment wear and tear, even equipment failure, and raise equipment maintenance costs. Therefore, the workshop work site should be kept clean, free of dust, corrosion and odorous gases. Reducing the impact of dust particles on products and equipment, ensuring the normal operation of equipment and personal health is particularly important.

Do you know why SMT uses a dust-free workshop? (Figure 4)

Through the construction of cleanrooms, at the fundamental level:

• Ensure the stability of equipment operation in the workshop and the accuracy of mounting;
• Ensure that the pads of the products processed during the manufacturing process are not contaminated by dust, which may affect the welding yield.
• Prevent the generation of static electricity due to the flow of large amounts of dust and environmental changes, which may cause ESD risks;
• Ensure that the indoor air is more hygienic and fresh, which is conducive to people's comfortable work and good health.
• Ensure product quality is under control and customer satisfaction.

Class X (at Y μm)
Here, X represents the grade of the dust-free workshop, such as 100 or 10000, etc., and Y represents the particle size, such as 0.2μm, 0.5μm, etc. Multiple selections are available. This means that the user stipulates that the particle content in the cleanroom must meet the limits of this grade within these particle sizes.

Here are a few examples:

• Class1 (0.1μm, 0.2μm, 0.5μm)
• Class 100(0.2μm, 0.5μm)
• Class 100(0.1μm, 0.2μm, 0.5μm)

In Classes 100 (M3.5) and Greater (Class 100, 1000, 10000....) Generally, one particle size is sufficient. In Classes Less than 100 (M3.5) (Class 10, 1....) Generally, it is necessary to consider several particle sizes.

The second one is to stipulate the status of the dust-free workshop, for example:

Class X (At Y μm), at-rest

The third one is to set the upper limit of particle concentration. Generally, during As-built cleanrooms, they are very clean, and it is difficult to test the particle control capability. At this time, you can simply lower the acceptance upper limit, for example:

• Class 10000 (0.3 μm ≤ 10000), As-built
• Class 10000 (0.5 μm ≤ 1000), As-built

The purpose of doing this is to ensure that the cleanroom still has sufficient particle control capabilities when it is in the Operational state.

The ISO14644 cleanliness grade standard classifies the air cleanliness levels in cleanrooms (areas) and related controlled environments based on the sole indicator of suspended particle concentration, and only considers the cumulative distribution of particle groups within the particle size limit (lower limit) range of 0.1um to 0.5um. According to particle size, they can be classified into conventional particles (0.1um to 0.5um), ultrafine particles (< 0.1um), and macro particles (> 5.0um).

Air cleanliness classification standard: ISO14644-1 (International standard)

Do you know why SMT uses a dust-free workshop? (Figure 5)

Air cleanliness classification standard: GB/T16292-1996 (Chinese Standard)

Do you know why SMT uses a dust-free workshop? (Figure 6)

• Special vacuum cleaner for clean rooms
• Clean paper, lint-free cloth
• Deionized water
• Alcohol
• Bucket
• Mop
• Mop special bucket

• When cleaning the walls inside a cleanroom, cleanroom dust-free cloths should be used.
• Prepare the cleaner with 90% deionized water and 10% isopropyl alcohol.
• Use approved cleanroom-specific detergents;
• Every day, the garbage bins in the workshop and preparation room should be inspected and cleared away in a timely manner.
• Each floor should be vacuumed. Each time a shift is handed over, the completion status of the work should be marked on the map, such as where it ends and where it starts.
• Special mops should be used to clean the floor of the clean room.
• When vacuuming in a clean room, a dedicated vacuum cleaner equipped with a high-efficiency filter should be used.
• All the doors need to be inspected and dried
• Mop the floor after vacuuming it. Clean the walls once a week.
• Vacuuming and wiping should also be done under raised floors.
• Clean the columns and support columns under the raised floor once every three months.
• When working, always remember to wipe from top to bottom, from the ground farthest from the door towards the door.

1. Change into the dedicated anti-static suit, put on the hat and mask, and after dust removal through the air bath suction channel, enter the clean room.
2. After preparing the cleaning tools and supplies and placing them at the designated locations, start the cleaning work.
3. Pick up ground garbage in the order arranged by the production line, from the inside out one by one.
4. Empty and clear the garbage in the trash cans and bins on time, conduct inspections, strictly classify it as required, and then transport it to the designated garbage room after being inspected by the production line administrator or security guard Internal classification placement.
5. Clean the indoor glass, walls and shelves from top to bottom using clean paper or lint-free cloth.
6. Use a clean dust mop to carefully push and clean the floor from the inside out. Clean the ground with a lint-free cloth in time if there is garbage, dirt, water stains, etc.
7. Use the rest and meal times of the production line workers to clean the production line, the ground under the workbenches and the seats.
8. Regularly clean the ceiling, air conditioning vents, ceiling light partitions, and under the raised floor. The cleaning procedures and materials used must be approved by the factory Affairs department, and holidays and breaks should be taken The gap is proceeding as planned.
9. The waxing of the cleanroom floor must be carried out strictly in accordance with the plan and cleaning procedures, and anti-static wax must be used.
10. After the cleaning work is completed, all cleaning supplies should be stored in the designated cleaning room separately from ordinary tools to avoid cross-contamination. They should be neatly arranged and must not be randomly placed in the clean room Indoor.

• Loose hoods, face masks, beard covers, shoe covers and latex gloves must be discarded and must not be reused.
• Requirements for employees' dress code and preparatory work.
• Personal items such as overcoats, hats, wallets and keys are not allowed.
• Employees should change into clothes and accessories that cause pollution.
• Employees should wear dust-free room hoods, gloves, rabbit fur coats and socks. Damaged or contaminated burqas or robes should be replaced immediately. Dress code should comply with the prescribed dress code procedures.
• No ordinary paper pads, notebooks, handbooks or writing tablets are allowed. Ordinary writing pencils, pens, erasers, crayons or chalks are not allowed. Take notes on cotton fluff paper, plastic paper or similar paper, and use ballpoint pens or other dust-free tools at the same time. The blue line marks, specifications or other instructions should be covered with plastic film, cotton fluff or other dust-free tools.

1. When walking in the clean room, movements should be gentle and running is not allowed to avoid affecting the laminar flow.
2. When working in a clean room, if the operation is paused, masks and gloves must not be removed for a short break.
3. Before entering the clean room, one must first pass through the dust washing room.
4. Staff entering the clean room must wear well-fitting dust-free clothes and shoes.
5. When it is necessary to sit, lie down or lie down during equipment maintenance, a special plastic sheet must be laid on the ground.
6. Before removing the dust-free suit, the following items must be removed first: mask, dust-free shoes, dust-free suit, hair mask, and gloves. They should be sorted and placed or discarded according to the labels.
7. The correct way to put on a mask is to fasten it with the buckle at the top of the back of the dust-free jacket hood.
8. Cleanroom staff are not allowed to bring non-dust-free laptops into the cleanroom.
9. Pencils are not allowed in the clean room. All writing must be done with ballpoint pens. When writing is incorrect, correction fluid must not be used to correct it.
10. The requirements for wearing a dust-free suit are that it should cover the mouth and nose, hair must not be exposed, the sleeves and mouth must cover the glove opening, and the wrists must not be exposed.
11. The raised floor in the clean room must not be lifted at will to avoid affecting laminar flow and personnel safety.
12. After getting dressed, you are not allowed to enter the monitoring room.
13. No one is allowed to use cosmetics (such as lipstick, blush, perfume, etc.) when working in the wafer area.
14. Precautions for entering the dust-cleaning room: Do not walk side by side. Two people must keep their bodies at least 30 centimeters apart, place their hands on their waists, and pass slowly. Running is strictly prohibited.
15. The way to reduce fine dust is to keep your head, hands and body clean.
16. When cleaning in the dust-washing room, the two people must keep a distance of more than 30 centimeters in front of and behind each other.
17. Before putting on the dust-free suit, you need to tie up your hair first and then put on the hair cover.
18. People are the biggest source of pollution in cleanrooms.
19. The last action of wearing a dust-free suit is to check the clothing.
20. The following stationery items are not exclusively for clean rooms: water-based signature pens, pencils, correction fluid, and photocopy paper.
21. All personnel entering the clean area are strictly prohibited from consuming anything (such as chewing gum).
22. No one is allowed to put items that are irrelevant to work and cannot be brought into the clean room in the bag of the dust-free suit.