Q: CNC makes the PCB as the shape on hand

CNC makes the PCB as the shape on hand Do you know that the PCB you receive from your supplier is not the size on those production equipment and go through all the processes? What we produce on equipment is the “working size” and after CNC the PCB becomes the “shipping size” of your design. Except to separate shipping size from working size, CNC is also used for shaping your PCB outline, the slot design in board, or bigger drilling hole that is oversized.

Q: Several Factors Affecting PCB RF Performance

Several Factors Affecting PCB RF Performance Nowadays, the electronic products have feature of SoC (System on Chip), all functions and performances are almost defined by IC. However, even with the same IC and functions, the products designed by different companies, still have different performance. What factors cause these differences? Here, we list several factors that contribute to the difference in performance. Metal: copper foil type and roughness, surface finish type (ENIG, HSAL…) Glass Fabric: different glass styles (106, 1080, 2113…etc.) and weave styles. DK (Dielectric constant) DF (loss tangent) Vias: Various via options for RF routing (buried via / blind via / backdrill)

Q: Can Drill Drawing Table(Drill Symbols) Replace NC Drill Files?

“Drill Drawing Table” What is drill drawing table? Drill drawing table is also known as drill drawing legend or drill table. The drill drawing table includes hole size, hole type, hole counts and so on. More importantly, each hole size of drill will be represented by a specific symbol or letter. “NC Drill Files” NC drill files stands for numeric control drill file which contains hole location, hole shape and hole size. NC drill files and Gerber file are two different files. Take “Altium Designer” for example, the outputs of design could be divided into “Gerber files” and “NC Drill Files”. If missing “NC Drill Files” during project evaluation stage, the production cost could be calculated but might be less accurate. However, the “NC Drill Files” is necessary once entering production phase. So can “Drill Drawing table” replace “NC Drill Files”? The answer is NO. Due to the drill drawing table can’t provide exact location of each hole. Without the coordinate information, the PCB manufacturer can’t set the drilling program for hole drilling. Thus, the “NC Drill Files” are required for PCB fabrication.

Q: Purpose of Back drill For Printed Circuit Board

Purpose of Back drill For Printed Circuit Board Back drillis a drill process for plated hole (via) on the PCB, the main purpose of back drill process is to reduce the length of the stub and its capacitance effect by eliminating the excess copper in the plated hole (via) on the PCB. By eliminating the excess copper in the plated hole, the transmission characteristics of high-speed signals can be improved, further increasing the transmission speed of high-speed connectors. Back drill can be applied to any type of circuit board where stubs cause signal integrity degradation, with minimal design and layout considerations. Now we’re going through the advantages of Back drill below: Reduced deterministic jitter Lower bit error rate (BER) Less signal attenuation with improved impedance matching Increased channel bandwidth Increased data rates Reduced EMI radiation from the stubs Reduced excitation of resonance modes Reduced via-to-via crosstalk Aspect ratio can be neglected (in contrast to blind vias)

Question 1

Quality Inspection for Outgoing PCBs

Accepted Answer

Purpose of OQC(Outgoing Quality Check)

After 100% of electric test and appearance check, the PCB manufacturer will conduct “Outgoing Quality Check” to ensure the quality of completed boards meet client’s requirements. Besides compliance with client’s requests, the process of OQC could optimize the production process and improve the quality by detecting the potential quality issue.

Sampling Inspection – MIL-STD-105E Level 2

The PCB manufacturer either follows client’s regulations or control plan to conduct quality inspection. If above not available, then the quality inspection will follow the PCB manufacturer’s standard. The strictness of quality inspection usually could be divided into two categories, automotive products or non-automotive products. Take ExPlus for instance, ExPlus follows MIL-STD-105E Level 2 for both categories. What is “MIL-STD-105E”? MIL-STD-105E stands for military standard 105E which has established for the acceptance or rejection of lots based on the assessment of items attributes. Based on the quantity of taken samples from the lot containing N units, the WHOLE lot is either accepted or rejected. For PCB used in automotive products, ExPlus follows “0 accepted 1 rejected” under MIL-STD-105E Level 2. Which means no matter how many units are inspected, the whole lot will be rejected if there’s one unit not meet the standard. On the other hand, ExPlus follows “MIL-STD-105E Level 2 0.65%” for non-automotive PCB boards. Take 1,000 units for example. Based on the below chart, if there’s only 1 unit not meet the standard within 80 units taken samples, then the whole lot is accepted. Again, sampling inspection is used for outgoing goods inspection after 100% of open circuit/broken circuit and appearance check are performed.

Question 2

CNC makes the PCB as the shape on hand

Accepted Answer

CNC makes the PCB as the shape on hand

Do you know that the PCB you receive from your supplier is not the size on those production equipment and go through all the processes?
What we produce on equipment is the “working size” and after CNC the PCB becomes the “shipping size” of your design.

Except to separate shipping size from working size, CNC is also used for shaping your PCB outline, the slot design in board, or bigger drilling hole that is oversized.

Question 3

Several Factors Affecting PCB RF Performance

Accepted Answer

Several Factors Affecting PCB RF Performance

Nowadays, the electronic products have feature of SoC (System on Chip), all functions and performances are almost defined by IC. However, even with the same IC and functions, the products designed by different companies, still have different performance. What factors cause these differences?

Here, we list several factors that contribute to the difference in performance.

Metal: copper foil type and roughness, surface finish type (ENIG, HSAL…)
Glass Fabric: different glass styles (106, 1080, 2113…etc.) and weave styles.
DK (Dielectric constant)
DF (loss tangent)
Vias: Various via options for RF routing (buried via / blind via / backdrill)

Question 4

On the PCB, besides BGA and SOP, are there other mainstream package types?

Accepted Answer

Basically, chip packaging is to put the substrate on a board, lead out the pins, and then fix them into a whole, it has the function of protecting the chip. It not only has fixed functions, but also increases thermal performance. Therefore, chip packaging is very important for circuits such as CPU.

Semiconductor packaging has undergone three times innovations: the first was from pin-insert packaging to surface mount packaging in the 1990s, which greatly increased the assembly density on the board; the second was the emergence of ball matrix packaging in the 2000s. It meets the market's demand for high pins and improves the performance of semiconductor devices; chip-level packaging, system packaging, etc. are the products of the third innovation, and its purpose is to minimize the packaging area. At present, the mainstream chip packaging types mainly include the following types: BGA, SOP, TSOP, SIP, etc.

BGA : Today, most high pin count chips use BGA. The contact surface between the BGA array ball soldering and the substrate is large and short, which is good for heat dissipation; the pins of the BGA array solder balls are very short, which shortens the signal transmission path, reduces the lead inductance and resistance, and the signal transmission delay is small, adapting to the frequency greatly improved, thus improving the performance of the circuit.

SOP : The typical feature of this type of package is that many pins are made around the packaged chip. The package is easy to operate and has relatively high reliability. It is one of the mainstream chip package methods.

TSOP : TSOP is suitable for routing on PCB with SMT technology. When the package size of TSOP is lower, the parasitic parameters (when the current changes greatly, the output voltage disturbance is caused) are reduced, which is suitable for high-frequency applications, and the operation is more convenient and the reliability is relatively high.

SIP : SIP package is to integrate multiple functional chips, including processors, memory and other functional chips into one package, so as to realize a basically complete function. SIP packaging is widely used in wireless communications, automotive electronics, medical electronics, computers, military electronics and other fields.

To sum up, packaging is an important step in the finished product of memory chips, and plays an important role in the yield rate and service life of chips.

Question 5

What Is ExPlus’ SOP When Encountering Client’s Complaint?

Accepted Answer

To complete PCB production, it involves various processes. As matter of fact, it’s unrealistic to say there’s no defect board during the process. To cope with possibility of shortage of delivery, the PCB manufacturer will calculate the backup rate before procuring the raw material in order to fulfill client’s order quantity. However, even if the PCB manufacturer proceeds "open circuit" and "short circuit" test, so called E-TEST, FQC, and OQC before delivery. But due to most of inspections are still conducted by personnel thus the chance of leaking the defect board is unavoidable. So, it’s crucial how PCB manufacturer deals with the situation when the defect board is found on the client’s site.

As being in PCB industry since 1997, ExPlus has it SOP when receiving client’s complaint. The SOP could be divided into several steps as below.

Step 1, The client provides the picture of complaining issue and the picture shall include the maker’s logo and D/C(Date Code, which identify which week the board was produced.) And the client informs the quantity of defect board, the process stage of the board, and handling of the defect board.

Step 2. After the contact window(usually the Sales Team) receives the information from the client, the Sales Team will fill out the CAR form(CORRECTIVE ACTION REPORT) and forwards to the relative departments which including but not limited to QA Team, Engineering Team and Purchasing Team.

Step 3. Upon receiving CAR from Sales Team, the QA Team shall check bellows.

Step 3.1 The information provided in the CAR form is complete or not? Whether the image can
define the root cause of defect. If not, the QA Team shall reply with feedback or comment back to the Sales Team.

Step 3.2 If the provided information and image is clear, then the QA Team will confirm whether the defect meets client’s regulations or IPC standard. If within standard, then the QA Team will return the CAR and provide with quoted IPC terms and supportive image. On the other hand, if the defect beyond the standard, then the root cause and CAR shall be replied within 24 to 48 hours. In the case that the issue is too complicated to be replied with 48 hours, then it shall be estimated the exact hours it will take and reply back to the client.

Step 4 If the defect board checked out to be makers’ responsibility, the case of customer complaint could be solved by multiple methods such as replacing with new boards, deducting the cost from repeating order and so on.

In fact, it takes time and also difficult to find out the root cause of NG board when the bare board is assembled. Thus, it’s best to inspect the bare board before assembly.

Question 6

Silk Screen Can Be Printed as Multiple Colors and Functions

Accepted Answer

The production method of printing silk screen on PCB is quite similar to solder mask.
They are both liquid to be printed and cured on PCB, and also different colors.
That’s right! Silk screen is not always white.
On white solder mask PCB, the silk screen can be black.
And sometimes other different colors may be used as well.

Function of silk screen can be separated as follows:

Identification
For PCB Designer: P/N, Symbol, Logo, Assembly Remark, Component Code, etc.
For PCB Maker: Manufacturing P/N, UL Logo, Serial Number, etc.

Record
For PCB Designer: Version of design, Date of design completion, etc.
For PCB Maker: Manufacturing date code, manufacturing version, etc.

Question 7

Can Drill Drawing Table(Drill Symbols) Replace NC Drill Files?

Accepted Answer

“Drill Drawing Table”
What is drill drawing table? Drill drawing table is also known as drill drawing legend or drill table. The drill drawing table includes hole size, hole type, hole counts and so on. More importantly, each hole size of drill will be represented by a specific symbol or letter.

“NC Drill Files”
NC drill files stands for numeric control drill file which contains hole location, hole shape and hole size. NC drill files and Gerber file are two different files. Take “Altium Designer” for example, the outputs of design could be divided into “Gerber files” and “NC Drill Files”. If missing “NC Drill Files” during project evaluation stage, the production cost could be calculated but might be less accurate. However, the “NC Drill Files” is necessary once entering production phase.

So can “Drill Drawing table” replace “NC Drill Files”?
The answer is NO. Due to the drill drawing table can’t provide exact location of each hole. Without the coordinate information, the PCB manufacturer can’t set the drilling program for hole drilling. Thus, the “NC Drill Files” are required for PCB fabrication.

Question 8

The Component & Solder Sides of PCBs

Accepted Answer

In the previous article, we have introduced the advantages of SMT, and the basic methods of PCB assembly (THM/SMT).

First of all, we define the side of the PCB with components as the Component side (Side C), and the other side without components and touches the solder mask called the Solder side (Side S). However, this expression has been used in the past we used to insert DIP components on a single side, therefore it is named “The side for insert DIP” and “The side for solder mask”. Until now, each side with components can either be named as “components side" or “solder sides”.

Nevertheless, how do define the name of each side during the production process?

Some designers called the part which included more components and IC “Component side”, and named the other parts which do not include IC components as “Solder mask”, also known as “Side A&B” or “Side C&S”. In conclusion, the name of sides depends on the designer.

*Related Article:
SMT1: The advantages/disadvantages about SMT
SMT2: Basic methods of PCB assembly: THM & SMT

Question 9

Purpose of Back drill For Printed Circuit Board

Accepted Answer

Purpose of Back drill For Printed Circuit Board

Back drillis a drill process for plated hole (via) on the PCB, the main purpose of back drill process is to reduce the length of the stub and its capacitance effect by eliminating the excess copper in the plated hole (via) on the PCB.

By eliminating the excess copper in the plated hole, the transmission characteristics of high-speed signals can be improved, further increasing the transmission speed of high-speed connectors.

Back drill can be applied to any type of circuit board where stubs cause signal integrity degradation, with minimal design and layout considerations.

Now we’re going through the advantages of Back drill below:

Reduced deterministic jitter
Lower bit error rate (BER)
Less signal attenuation with improved impedance matching
Increased channel bandwidth
Increased data rates Reduced EMI radiation from the stubs
Reduced excitation of resonance modes
Reduced via-to-via crosstalk
Aspect ratio can be neglected (in contrast to blind vias)

Question 10

The design requirement of COB

Accepted Answer

In the previous article, we have introduced what is the COB process, wire bonding, and wire pull test. In this article, we’re going to talk about the design requirements of COB.

1.The surface finish should be either gold plating or ENIG to provide the requirement of Die Bonding, and the thickness of gold plating is usually larger than general.

2. The consistency of length of wire should be considered. In other words, to spread the risk of short circuit, the manufacturer have to keep the same distance from solder joint to Die and PAD. Shorten the spacing can avoid the appearance of diagonal PADs, and designing elliptical PAD also be helpful to equally divide the bonding wires into the relative positions.

3. Additionally, one wafer should have more than two positioning points, and replace the round hole with a cross shape. Wire Bonder is automatic-control, due to the restriction of the machine, the engineer should consider the function while setting the positioning points.

4. The Die Pad of the PCB should be bigger than the actual size, not only can control the shift of the die but also avoid the over-revolve in the die pad. The suggestion is every die pad on the board should be larger than the actual size.

5. It would be better not set vias in the potting area, or require the PCB manufacturer to plug those vias completely. The purpose is to avoid epoxy filters with the other side of the board.

6. For the convenience of dispensing and dispensing control, it is suggest to print the silkscreen on the areas which need epoxy.

*Related Article:
COB1:What is COB (Chip On Board)? Introduce the Evolution History of COB
COB2:Brief Introduction Process of COB (Chip On Board)
COB3:Introduce COB's bonding wire and its pulling force

Knowledge