The wiring chart behind the physical PCB and manufacturing plant drawings are two things. The manufacturing plant drawings describe the physical properties and electrical properties in the "Gerber Data File" circuit diagram. These two files are complementary.
Memorandial needs to define options and exceptions
Although there are some specifications to drive the PCB design process, in these specifications, options are almost unlimited. Everything has rules, but almost all rules have exceptions. Define these options and rule exceptions to a work of memo.
Illustrative memo: unless otherwise specified
"Unless otherwise specified" is the ambiguity term that allows the rules to implement hierarchical level. Legal documents and contract documents are the highest arbitrator of the PCB manufacturing process, followed by supportive procurement orders, and then the specific design description of the pyramid structure, the design notes here include manufacturing drawings and assembly drawings, this article is not described later.
IPC-6012 defines general precautions for the manufacturing of rigid boards, and IPC-6013 is for flexible circuit boards, and IPC-600 is a comprehensive document relating to all processes. By citing each other, the standard for PCB manufacturing is as many as dozens - unless otherwise specified. Therefore, the purpose of our creation of the descriptive memo is to increase the manufacturability design (DFM) while do not violate local laws, contracts and purchase orders.
Each annotation in the manufacturing drawings should define the uniqueness of the particular board, first, the PCB level should be defined.
Let's first explain the meaning of "level".
Level The word depends on the expected use scene and is based on failure - punishment mode. For example, if a toy helicopter's battery connector is falling off, the plane can't take off, the little guy may cry, the child is crying after all, can be classified as a grade 1. We can tolerate this failure.
Let's take a look at the level 2. If a real estate agent is using a new resort with drone, the result is sad, the drone hits the ground lawn, which can only be a video that lacks important fragments. At this time, it is an adult, which can be returned to level 2. In this way of use, we should implement level 2, not level 1, even if it can save drone costs. We should define grades 2 for most applications.
Then, there is a level 3
Now I imagine, if the Marine Corps No. 1 is carrying a big person (no one here), if it suddenly outsorganizes, turn around in a rose garden, the garden owner will definitely be very unhappy. We should advance the requirements of the PCB to the level 3. In fact, I just learned that the security level of avionics is 3A, which also applies to the automatic driving car I am currently studying.
Basically, we can't hurt when it comes to personal safety.
Safety Level 3 has added a lot of test items, and suppliers can perform a complete set of tests. The tolerance of defects is getting lower and lower, and the reliability will become higher and higher. Of course, the price will rise high, but we want to live in such a world.
A key difference in these levels is reflected in how the plating holes are bound to the positioning pad. Directly follow the relevant IPC specification to get this picture. Level 1 is the worst performance of performance, and half of the fifth is distributed on the pad. Level 2 is "broken", the level 3 pad is not damaged. In fact, in the grade 3, some metal should be left on the drilling. Many designs follow the level 2, but all specify the cutting mode without allowing "breaking", this additional requirement will be recorded in a memo.
We can see that the specification makes us walk in the right direction. The large direction is set, we also need to solve detail problems such as solder weld membrane, oil print color, dielectric, electroplating ingredients, packaging, and transportation, and any other requirements for specification or not included in the specification. The norms have almost all all things, but the industry's progress is sometimes leading to standard organizations. For example, there are currently two working groups that are developing organic surface protection (OSP), but there is currently no related files to define this process. As a customer, you need to discuss with your manufacturer's factors that are not included in the norms, and then help you clarify these details.
Let's talk about why you need to pay attention to these norms and exceptions, because you are determining a comprehensive illustrative note that can guarantee accuracy and manufacturability design.
Examining the manufacturability design from money, you will recognize that every description increases costs or cost savings, depending on the actual application requirements and the final application scenario. Unnecessary memos will cause the manufacturer to bear the burden, and missing some may lead to recall.
Some people think that we need to follow the principle of Okham razor, the less annotation and standardization, the effect is about a good effect. Another view of the camp believes that we need to take into account each possibility and a comment is defined for all things that may have faults to prevent it from happening again. There are no other things in the first page of Qualcomm, manufacturing plant, all are comments.
I recorded this standard memorandum list and then deleted some comments that were not applicable to the current board. Here, I am not a loud call. Everyone is done in accordance with Qualcomm - architects need to consider so comprehensive. The specific content is as follows:
Note: Unless otherwise specified
1. Follow the standards:
A. Make a PCB according to the current revision of IPC-6012 level 2.
B. Interpretation and tolerances based on the current revision of ASME Y14.5M.
C. Do not enlarge the drawing.
2, material:
A. FR4 TG 180 C or equivalent material.
B. The same material should comply with ROHS standards, halogen, and approved by your company.
C. The thickness of a single copper foil should be located within the range defined in the stack. View details A.
3, flatness:
A. Assembly panels or monolithic bows and warpage must not exceed 0.025 mm / mm.
B. Test according to the 2.4.22 section of the IPC-TM-650 current version.
4. Etching geometry:
A. Measure the width on the basis of metallization.
B. The minimum line width: outer layer 0.NN mm, inner layer 0.NN mm.
C. The final line width and the end area will not deviate from the main pattern image +/- 0.025 mm or 20% of 1 to 1, and the comparison of the minimum values of the above two.
5. Surface treatment: (Select appropriate surface treatment (ES))
A. Chemical nickel palladium plating is carried out according to the current revision of IPC4556. Stateless metal can choose 118-236 microbiochemical nickel, 2-6 microbiochemical palladium, and 1.2 microse inch gold.
B. Chemical Shenjin plating according to the current revision of IPC-4552. Exposure Metals can choose from 118-236 micron inch chemical nickel and 2-5 microchanum gold.
6. Destructive test:
A. Some samples and reports should be provided to your company's design engineering departments.
B. Each shipment requires a solder sample used in a lead-free welding process.
C. X-OUT panel can be used for welding samples.
7. Filled:
A. The electroplating material in the hole should be a continuous electrolytic copper, a minimum thickness of 0.025 mm.
B. Minimum hole size: 0.Nn mm.
C. Measure the hole size after electroplating.
D. View Drilling Charts, determine the dimension and tolerances.
E. The location of all holes should be in the range of 0.08 mm in the real location provided by CAD data.
8. Welding layer:
A. Swelding layer (SMOBC) is realized on the main surface and the secondary naked copper according to the IPC-SM-840 current version of the IPE B.
B. Color: dumb green
C. Liquid photocatalysis (LPI) solder resist thickness is between 0.001 mm to 0.002 mm, halogen
D. Long leakage is not allowed on the exposed SMD pad.
E. There is no exposed wire.
9. Wire print layer:
A. The main surface and the secondary wire printing layer use a white epoxy resin, non-conductive non-nutrient ink.
B. Any unspecified silk screen width should be 0.13 mm
C. Make sure the silk printing layer does not contact any exposed metal.
D. Vendor Date Code, LOGO, unordered list, and any additional tags are located in the secondary.
10. Remove any radius greater than 0.003 mm glitch and pointed edge.
11. Non-destructive assessment:
A: All printed wiring boards (PWBs) must be 100% via an electrical test defined by IPC-356 NetList to comply with the level 2 requirements in IPC-9252 amendments.
B. The qualified certificate should be provided with each cargo.
12. Scrapped board:
A. The scrapped board that does not meet all specifications is identified using permanent markers on both sides of the PCB.
B. The products without any newspapers will be packaged together.
C. Products with n or less scrap plates should be packaged separately from products that do not include waste plates.
D. Products that exceed N news scrap pad should not be packaged.
13. Packaging requirements:
A.PWBS should be packaged in an internal container in a vacuum seal.
B. The external container should be sufficient to prevent damage during transportation and handling.
14. Impedance (all impedance tolerances are within 10% of the positive and negatives)
A. All the wire impedance of all 0.Nn mm wires on the outer layer should be 50 ohms.
B. The differential impedance of all 0.Nn mm wide /0.nn millimeter spacing on the outer layer should be 90 ohms.
C. The differential impedance of all 0.Nn mm wide /0.nn millimeters on the inner layer should be 90 ohms.
D. The supplier can adjust the design geometry of up to +/- 20% to achieve the target impedance. The wire width, spacing or dielectric thickness is adjusted to more than 20%. It needs to be approved by your company's engineering department.
English Originally from the website Supplyframe-Hardware, author John Burkhert Jr
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