Q: What Is Pre-treatment Before Inner Layer Process?

What Is Pre-treatment Before Inner Layer Process? After cropping process to have PCB material ready as working size, the first step we will scrub the surface of material to clear contamination and conduct micro-etching to enhance the adhesion with dry film in the next process of PCB material surface. And to plus curing to dry material, all three minor processes are so-called pre-treatment.

Q: What is COB (Chip On Board)? Introduce the Evolution History of COB

COB (Chip On Board) has already been a mature technology in the electronics manufacturing industry. Previously, COB was mostly only used in some low-end consumer products. However, as electronic products become smaller and smaller, the COB process can be used for smaller space more than IC. COB is to transplant the wire bonding and capsule operations of IC packaging to the circuit board, and re-adhere the die that was originally pasted to the lead-frame to the PCB. Re-solder the wires that were originally bonded to the lead frame to the gold-plated pads of the PCB, and then use Epoxy to cover the wafers and wires to replace the original mold package. The advantages of COB COB can save the original IC packaging Trimming & Form and marking processes, and it can also reduce the cost of the IC packaging factory's sales and marketing, so basically its process will be cheaper than the IC packaging process.

Q: How to Have PCB Material Ready?

Differs from PCB design and PCB specification, different PCB material could be used for different applications of PCB design. Before cropping the PCB material, some important features of material such as the material brand, TG (Glass Transition Temperature) value requirement, level of DK (Dielectric constant) and DF (Dissipation Factor) value, and copper thickness will be listed on the OP to be confirmed in advance that PCB makers do start PCB productions with the correct PCB material. When it comes to production, the first process for PCB makers is to crop the material into working size in most efficient way in order not to waste extra material. By increasing the material usage could help customer to save more cost on PCB. After the cropping process, the material in working size is ready to go!

Question 1

Brief Introduction Process of COB (Chip On Board)

Accepted Answer

The key technique of COB (Chip On Board) is Wire Bonding and Molding, which is the process to package exposed integrated circuit (IC) as electronic component. The integrated circuit (IC) to extend its I/O through trace of package by Wire Bonding, Flip Chip, or Tape Automatic Bonding (TAB).

The process of COB is as follows.

Rework
↓
Die In → Clear → Dispensing → Die Attach → Curing → Wire Bond → Testing → Coating → Curing → Visual Check → Testing → FQC → Packing → Delivery
↑
Rework

Environmental requirement of COB – Clean Room

The Clean Room class must be above class 100000. Normally the Clean Room class of IC package testing shall be class 10000 or even class 1000. Clean Room for Wafer Fabrication is even higher.

*Related Article:
What is COB (Chip On Board)? Introduce the evolution history of COB

Question 2

Where are printed circuit boards used? III

Accepted Answer

PCBs are used in many different sectors. We have introduced the applications in telecommunication, consumer electronics.

Today we are talking about some applications in medical devices, which are highly specialized, such as HDI PCB, Flex PCB, and Rigid-Flex PCB. The using of medical devices are getting higher and higher during COVID-19.

Monitors: Healthcare monitors such as heart rate, blood pressure, blood glucose monitors, and forehead thermometer require single or double sides PCB most.
Scanning Equipment: Such as CT, CAT, ultrasonic scanners, and X-Ray screen often use PCBs.
Internal Devices: Heart pacemakers and similar internal medical devices will require small, HDI, flex, or rigid-flex PCBs.

*Related Article:
Where are printed circuit boards used?
Where are printed circuit boards used? II

Question 3

Does PCB have expiry date? Or long shelf life?

Accepted Answer

From time to time, clients will ask us is there any suggestion if they’re going to assemble the PCB which have received years ago. Our advice to them is baking before assembly.

PCB Should stay in vacuum package before assembly
Once the PCB delivered to clients, it’ll be arranged for assembly after IQC. But if the PCB isn’t scheduled for assembly just yet, please keep the board as packed condition. The vacuum package could prevent the board from absorbing moisture and keep the PCB in good condition.

Golden Time for PCB assembly after packed

So If PCB is packed, under temperature 23 +/-2 C/RH. 50~60%, we suggest assembly within half a year for PCB with HASL surface finish.
For PCB with OSP and Immersion Silver surface finish, the ideal assembly time is within a month after packed.
And for PCB with Immersion Tin and Immersion Gold surface finish, our suggestion will be 2 months.

Usually, when PCB stores over 2 months, it’s best to bake before assembly.
If you’re interested in this topic, you might find below article interesting as well.

Why long stored PCB shall be baked before assembly.

bake pcb before assembly if stores over 2 months, suggested by ExPlus PCB

bake pcb before assembly if stores over 2 months, suggested by ExPlus PCB

Question 4

What Is Pre-treatment Before Inner Layer Process?

Accepted Answer

What Is Pre-treatment Before Inner Layer Process?

After cropping process to have PCB material ready as working size, the first step we will scrub the surface of material to clear contamination and conduct micro-etching to enhance the adhesion with dry film in the next process of PCB material surface. And to plus curing to dry material, all three minor processes are so-called pre-treatment.

Question 5

Brief Talk about PCB Materials

Accepted Answer

When it comes to basic PCB designing and producing, there are various choices for PCB material like FR and CEM series. Do you know how to pick the one that suits you well?

Here, we will list the basic differences between the common materials.

FR series – The most popular material.
FR stands for “Flame Retardants”, which is a glass fiber epoxy laminate material that meets the UL94v-0 fire standard set by UL. The differences between material FR series (such as FR-1, FR-2 and FR-4) are their thermal properties, heat resistance and electrical strength. FR-4 is suitable and widely used from single-layer to multi-layered PCBs.

CEM series – Low grade but widely used for single / double-layer PCB.
Such as CEM-1 and CEM-3. CEM-1 is composite material composed of woven glass fabric and paper core combined with epoxy resin. Widely used for single-layer PCBs; and CEM-3 is made of glass cloth and glass mat composite substrate material, which developed on the basis of FR-4. For double-layer PCBs, it is a great alternative to FR-4.

Comparison of prices for the above materials: FR-1 < FR-2 < CEM-1 < CEM-3 < FR-4

So far, the material FR-4 is still the best choice for PCB production due to its cost-efficiency and good characteristics. And CEM-1 is the first choice of LED lighting manufacturers, because it has achieved the best balance between heat dissipation performance and cost.

Question 6

What is COB (Chip On Board)? Introduce the Evolution History of COB

Accepted Answer

COB (Chip On Board) has already been a mature technology in the electronics manufacturing industry. Previously, COB was mostly only used in some low-end consumer products. However, as electronic products become smaller and smaller, the COB process can be used for smaller space more than IC.

COB is to transplant the wire bonding and capsule operations of IC packaging to the circuit board, and re-adhere the die that was originally pasted to the lead-frame to the PCB. Re-solder the wires that were originally bonded to the lead frame to the gold-plated pads of the PCB, and then use Epoxy to cover the wafers and wires to replace the original mold package.

The advantages of COB

COB can save the original IC packaging Trimming & Form and marking processes, and it can also reduce the cost of the IC packaging factory's sales and marketing, so basically its process will be cheaper than the IC packaging process.

Question 7

Where are printed circuit boards used? II

Accepted Answer

PCBs are used in many different sectors. We have introduced the applications in telecommunication. Today we are talking about some applications in consumer electronics products, which are the bigger part of our daily lives.

Communications devices: Smartphones, smart watches, radios and other communications products require PCBs.

Home appliances: Such as televisions, refrigerators, telephones, and so on require 2-4 layers PCB.

Entertainment: computers, DVD players, audio equipment, and so on.

*Related Article:
Where are printed circuit boards used?
Where are printed circuit boards used? III
Where are printed circuit boards used? IV
Where are printed circuit boards used? V

Question 8

From MetaVerse to AR/VR Application Introducing HDI (High Density Interconnect) PCB

Accepted Answer

Metaverse x AR/VR application

Ever since Facebook(Meta) announced its “Metaverse Grand Mission”, it has been a popular issue in the electronic industry. Many electronic products could be derived from the idea of “Metaverse” such as AR and VR device. For a reliable VR or AR wearable device, it might requires faster network speed, more powerful graphic processor and so on. Thus, the product developer will choose HDI PCB rather than Rigid PCB as its key electronic component.

AR/VR application x HDI PCB HDI PCB stands for High Density Interconnect PCB. And HDI is a kind of PCB technology which generated from the requirement of higher wiring density with smaller PTH/NPTH holes, higher connection pad density and finer line width and spacing.

The features of HDI PCB are light, thin, and short which makes it an ideal electronic component for wearable device. With previous mentioned advantages, it could increase the trace density, facilitate the use of advanced packing technology, and greatly improves the signal out performance. That’s why product developer or designer will choose HDI PCB over than conventional Rigid PCB for its key electronic component.

If you’re interested in wearable device or HDI PCB, please check below relevant articles.

1.HDI PCB and its application
2.Smart Watch
3.NPTH, PTH Holes

Question 9

How to Have PCB Material Ready?

Accepted Answer

Differs from PCB design and PCB specification, different PCB material could be used for different applications of PCB design. Before cropping the PCB material, some important features of material such as the material brand, TG (Glass Transition Temperature) value requirement, level of DK (Dielectric constant) and DF (Dissipation Factor) value, and copper thickness will be listed on the OP to be confirmed in advance that PCB makers do start PCB productions with the correct PCB material.

When it comes to production, the first process for PCB makers is to crop the material into working size in most efficient way in order not to waste extra material.

By increasing the material usage could help customer to save more cost on PCB. After the cropping process, the material in working size is ready to go!

Question 10

The basic composition of Printed Circuit Board (PCB)

Accepted Answer

A complete Printed Circuit Board (PCB) is consist of different parts, and each has its own function and purpose. If you are interest in this product and industry. Let’s read the following introduction and learn more!

Pattern: The Pattern refers to the traces on PCB, which are used for circuit conduction between components, and a large copper surface is also designed as a ground and power plane.

Dielectric: The dielectric is used to maintain the insulation between the circuit and each layer, also known as base material.

Through hole: Also known as Via, which is used to connect the circuit between different layers. The larger sized via is used for insert component, also, there is non-plating through hole (NPTH), which is used for positioning while SMT process and fixing screws while assembling.

Solder resistant/Solder Mask: Not all the copper surfaces need to be mounted components, thus, the non-mounted copper surface area will be applied a layer of solder mask (epoxy liquid material) to avoid short circuit occur.

Legend/Marking/Silk screen: This is a non-essential part, the main purpose is only for marking the name, position frame for mounting components, so as to facilitate maintenance and identification after assembly.

Surface Finish: Because the copper surface is easily oxidized when exposed to air, and it will lead to poor solderability. Thus, it will be applied a layer of surface finish to protect the copper surface. There several type of surface finish like: HASL, ENIG, Immersion silver, Immersion Tin, OSP…etc. Each of them has its own plus and minus. We will discuss this topic in a later article.

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