Q: What Is Halogen-Free FR-4 Material?

In the previous topics, we have talked about “ How to choose the material of PCB? ”, “ Brief Talk about PCB Materials ”, and “ How to Have PCB Material Ready? ”. Today let’s discuss Halogen-Free FR-4 material. What Is Halogen-Free FR-4 Material? Defined by IPC and IEC, only BR(Bromine) and CL(Chlorine) content is less than 900 PPM, and the total of BR(Bromine) CL(Chlorine) content is less than 1500PPM, can be considered as Halogen-Free FR-4. Meanwhile, all materials used must meet the halogen-free requirements when using Halogen-Free FR-4. Halogen-Free FR-4 vs. Lead-Free FR-4 The grade of Halogen-Free FR-4 is greater than Lead-Free FR-4. Halogen-Free FR-4 basically meets the requirements for lead-free assembly. On the other hand, Lead-Free FR-4 that meets the requirements for lead-free assembly does not necessarily meet the requirements for Halogen-Free. As you might know there’re many types of PCB material. And choosing the suitable material will affect the durability and reliability of end products.

Q: Why are PCBs designed stack-up?

PCB stack-up design is a process of arranging the layer configuration of a multi-layer printed circuit board (PCB). This design considers various factors including electrical performance, signal integrity, EMI (electromagnetic interference), and thermal management. The primary purpose of stack-up design is to maximize the performance and reliability of the PCB. PCB stack-ups are necessary for several reasons: Electrical Performance : In high-speed and high-frequency applications, stack-up design ensures stability and consistency in signal transmission. By controlling the distances and arrangements between signal layers, ground planes, and power planes, signal transmission losses and crosstalk can be reduced, thereby enhancing electrical performance. Signal Integrity : In multi-layer PCBs, couplings and interactions exist between signal layers. Proper stack-up design can mitigate interference between signal layers, improve signal integrity, and reduce signal distortion and jitter. EMI Suppression : Rational PCB stack-up design can reduce electromagnetic radiation and external interference (EMI) of the PCB. Proper spacing between layers and distribution of copper foils between layers can enhance PCB's EMI suppression capability. Thermal Management : In high-power applications, stack-up design can aid heat conduction and dissipation. By adding thermal heat spreaders or copper foils at appropriate locations, PCB heat dissipation can be facilitated, preventing overheating and damage. In summary, stack-up design aims to ensure high performance, reliability, and stability of the PCB while meeting specific requirements of diverse applications. The reasonable stack-up design optimizes PCB's design and performance to the fullest extent.

Q: ¿Por qué no se recomienda utilizar PCB que supera el período de validez?

Debido al alto riesgo de oxidación y caída de componentes. Cada acabado superficial tiene un tiempo de montaje recomendado y unas condiciones de almacenamiento, las placas que superen el periodo de almacenamiento provocarán la oxidación del acabado superficial y también el alto riesgo de caída de los componentes durante la alta temperatura de montaje. El retrabajo recomendado De acuerdo con las condiciones de almacenamiento recomendadas, el fabricante no puede garantizar su calidad si las placas de circuito impreso han superado el tiempo de almacenamiento. Una vez que las placas superan el tiempo de almacenamiento, se recomienda un retrabajo, como hornear antes del montaje o volver a aplicar el acabado superficial, puede consultar nuestro artículo anterior para obtener más información: https://www.explus.com.tw/es/faq/why-does-long-stored-pcb-need-to-be-baked.html Sin embargo , no todos los materiales son adecuados para el retrabajo, la fuerza de unión del PP entre las capas disminuirá con el tiempo. Cuando se realiza el proceso de retrabajo en el horno, se puede correr un alto riesgo ya que aquellas placas que han pasado su vida útil pueden causar problemas de delaminación y formación de ampollas. -

Question 1

Can ENIG Replace ENEPIG for Wire Bonding?

Accepted Answer

When it comes to wire bonding, the first choice could be ENEPIG. ENEPIG seems to be the most stable one for wire bonding, however, the production cost is much higher than other surface finish. Here is one solution of using ENIG instead of ENEPIG by increasing the thickness of Au to 5u”.
See below pulling test condition and result of showing performance of using ENEPIG and ENIG.

Test condition:
To use 1.0 mil gold wire and pull strength to be above 3 grams force. (as TM-650 2.4.42.3)
PCB A is as ENEPIG finish with Ni:200u”; Pd:2u”; Au:2u”
PCB B is as ENIG finish with Ni:200u”; Au:5u”

Result:
PCB A: 5.091 ~ 11.186 (g)
PCB B: 4.432 ~ 12.030 (g)

To sum up, both ENEPIG and ENIG are ok for wire bonding.

Question 2

Introduction to CCL

Accepted Answer

CCL is primarily divided into three categories.

The first is high-frequency, the second is high-speed, and the third is standard.
There are three main standards to distinguish this categories:

Df (Dielectric Loss): The loss of electrical signals within the material.
Dk (Dielectric Constant): The delay of electrical signals within the material.
Tg (Glass Transition Temperature): The heat resistance of CCL.

Basic standards are as follows:

Df < 0.005 is high-frequency.
Df between 0.005 and 0.01 is high-speed.
Df > 0.01 is Standard.

The higher the grade of the CCL, the lower the values of Df and Dk, resulting in less signal loss and delay. This means the technical requirements and the added value will be higher, naturally leading to higher profit margins and unit prices. If we want to divide it further, there are a total of six categories. Among them, automotive use is related to safety, so it will be classified as high-frequency CCL with 5G, high-speed CCL is used in servers and switches, and standard CCL is generally used in consumer
electronics.

Major Advantages of High-Frequency CCL

High efficiency
Fast speed
Good control
Strong durability

In the manufacturing process, resin, catalyst, and curing agent are first mixed, then applied to fiberglass cloth. This is bonded with PP and covered with copper foil to form the so-called copper-clad laminate.

In terms of cost proportion, CCL as a whole accounts for about 67% of the overall proportion of PCB, and the cost proportion is relatively high.

Question 3

What Is Halogen-Free FR-4 Material?

Accepted Answer

In the previous topics, we have talked about “How to choose the material of PCB?”, “Brief Talk about PCB Materials”, and “How to Have PCB Material Ready?”. Today let’s discuss Halogen-Free FR-4 material.

What Is Halogen-Free FR-4 Material?
Defined by IPC and IEC, only BR(Bromine) and CL(Chlorine) content is less than 900 PPM, and the total of BR(Bromine) CL(Chlorine) content is less than 1500PPM, can be considered as Halogen-Free FR-4. Meanwhile, all materials used must meet the halogen-free requirements when using Halogen-Free FR-4.

Halogen-Free FR-4 vs. Lead-Free FR-4
The grade of Halogen-Free FR-4 is greater than Lead-Free FR-4. Halogen-Free FR-4 basically meets the requirements for lead-free assembly. On the other hand, Lead-Free FR-4 that meets the requirements for lead-free assembly does not necessarily meet the requirements for Halogen-Free.

As you might know there’re many types of PCB material. And choosing the suitable material will affect the durability and reliability of end products.

Question 4

PTH Killer – Some Common Plating Void Factors

Accepted Answer

PTH Killer – Some Common Plating Void Factors

You may know that the most serious problem of PTH is void at where copper should be plated on. But do you know why this is happening? The common factors could be on material, drilling process, or plating process.

1) Material: The CTE of material is not suitable for the plating process. Compare to leaded process in the old times, the recent lead free process is having higher CTE requirement of material. If the material was still suitable for only leaded process, it might lead to void when it applies to lead free process.

2) Drilling Process: After drilling process there will be remaining dust on the material. When the vacuuming machine doesn’t function well that dust is still in the hole, there might be having high chance of leading to void after plating process.

3) Plating Process: When the board enters the plating liquid, bubbles will occur in the hole. Although the plating machine will vibrate to shake off the bubbles, the bubbles may still exist due to not precise parameter or some other reasons. And the bubbles, of course, will lead to void after plating process just the same idea as drilling dust remaining.

Question 5

PCB Vias with epoxy filling before plating.

Accepted Answer

You may have heard of the PCB plugging process. Why use epoxy resin to block PCB vias? What are its pros and cons?

Improved Thermal Conductivity:
Epoxy filling enhances the thermal conductivity of the via, allowing for better heat dissipation within the PCB. This is particularly beneficial for high-power applications or designs with components that generate significant heat.
Enhanced Signal Integrity:
Epoxy filling helps to reduce signal loss and electromagnetic interference (EMI) by improving the integrity of high-speed signal transmission. It minimizes signal reflections and crosstalk, leading to improved overall signal quality.

Improved Electrical Isolation:
Epoxy filling helps to enhance electrical isolation between adjacent layers of the PCB, reducing the risk of short circuits and ensuring proper isolation between different signal or power domains.

It's worth noting that while epoxy-filled vias offer these benefits, they also introduce some challenges. For example, they can be more expensive to manufacture compared to non-filled vias, and the process may require additional steps and specialized equipment. Additionally, if rework or repair is necessary, epoxy-filled vias can be more difficult to modify. Therefore, the decision to use epoxy-filled vias should consider the specific requirements and constraints of the PCB design and application.

Question 6

Why are PCBs designed stack-up?

Accepted Answer

PCB stack-up design is a process of arranging the layer configuration of a multi-layer printed circuit board (PCB). This design considers various factors including electrical performance, signal integrity, EMI (electromagnetic interference), and thermal management. The primary purpose of stack-up design is to maximize the performance and reliability of the PCB.

PCB stack-ups are necessary for several reasons:

Electrical Performance: In high-speed and high-frequency applications, stack-up design ensures stability and consistency in signal transmission. By controlling the distances and arrangements between signal layers, ground planes, and power planes, signal transmission losses and crosstalk can be reduced, thereby enhancing electrical performance.

Signal Integrity: In multi-layer PCBs, couplings and interactions exist between signal layers. Proper stack-up design can mitigate interference between signal layers, improve signal integrity, and reduce signal distortion and jitter.

EMI Suppression: Rational PCB stack-up design can reduce electromagnetic radiation and external interference (EMI) of the PCB. Proper spacing between layers and distribution of copper foils between layers can enhance PCB's EMI suppression capability.

Thermal Management: In high-power applications, stack-up design can aid heat conduction and dissipation. By adding thermal heat spreaders or copper foils at appropriate locations, PCB heat dissipation can be facilitated, preventing overheating and damage.

In summary, stack-up design aims to ensure high performance, reliability, and stability of the PCB while meeting specific requirements of diverse applications. The reasonable stack-up design optimizes PCB's design and performance to the fullest extent.

Question 7

How do PCB Manufacturer Trace Each Production?

Accepted Answer

When client complaint happens, the PCB manufacturer needs to find out the root cause of the problem and prevent it from happening again. However, how to distinguish the defect board from specific production will be essential.
In order to trace each production, the PCB manufacturer will put Date Code and its LOGO on the PCB board. Date code will show when the PCB board is produced. And the manufacturer’s logo will show which PCB manufacturer produces the PCB board. For example, Date code 2316 means the PCB board is produced on the 16th weeks of year 2023. And below “EP AB 94V-0” is the manufacturer’s logo. Once the PCB manufacturer sees its logo and Date code, they could trace the PCB board and start the root cause analysis.

Question 8

Prueba de Confiabilidad - Prueba de Vida Acelerada

Accepted Answer

Aparte de la prueba de epsilometría (E-test) y otras pruebas múltiples, también hay pruebas avanzadas para la fiabilidad de PCB que se llama prueba de envejecimiento o prueba de vida acelerada.
Para aquellas aplicaciones que necesitan mucho tiempo de trabajo sin fallos, este tipo de pruebas puede ayudar a averiguar si PCB puede soportar la abrasión de la operación y el tiempo.

Algunas pruebas de simulación de ambiente se pueden hacer para verificar la confiabilidad del material por nuestra temperatura programable y cámara de humedad.

Aquí están las pruebas y las condiciones de prueba que hacemos:
Prueba de alta temperatura y alta humedad
Objetivo: Comprender la influencia de la absorción de humedad en la confiabilidad del material mediante simulación ambiental.
Condición: 85°C / 85% (Temperatura / Humedad)
Tiempo de prueba: 168 horas a 2000 horas (168 horas aproximadamente equivalen a 875 días)

Question 9

¿Por qué no se recomienda utilizar PCB que supera el período de validez?

Accepted Answer

Debido al alto riesgo de oxidación y caída de componentes.

Cada acabado superficial tiene un tiempo de montaje recomendado y unas condiciones de almacenamiento, las placas que superen el periodo de almacenamiento provocarán la oxidación del acabado superficial y también el alto riesgo de caída de los componentes durante la alta temperatura de montaje.

El retrabajo recomendado

De acuerdo con las condiciones de almacenamiento recomendadas, el fabricante no puede garantizar su calidad si las placas de circuito impreso han superado el tiempo de almacenamiento. Una vez que las placas superan el tiempo de almacenamiento, se recomienda un retrabajo, como hornear antes del montaje o volver a aplicar el acabado superficial, puede consultar nuestro artículo anterior para obtener más información:
https://www.explus.com.tw/es/faq/why-does-long-stored-pcb-need-to-be-baked.html

Sin embargo, no todos los materiales son adecuados para el retrabajo, la fuerza de unión del PP entre las capas disminuirá con el tiempo. Cuando se realiza el proceso de retrabajo en el horno, se puede correr un alto riesgo ya que aquellas placas que han pasado su vida útil pueden causar problemas de delaminación y formación de ampollas.

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Question 10

Los métodos de embalaje para Flying Lead, TAB y COF

Accepted Answer

PCB flexible: También conocido como placa de circuito impreso flexible (FPC).

En un artículo anterior, presentamos el cobre recocido laminado (RA) y el cobre electrodepositado (ED).
Hoy, hablemos sobre el método de embalaje Flying Lead.

Flying Lead es un método de empaquetado para placas flexibles/placas flexibles de alta densidad, que se refiere al método de diseño y fabricación de un conector que se utiliza para conectar PCB con otros dispositivos o sistemas. No es específico de un tipo particular de PCB o método de empaque. Por lo tanto, Flying Lead se puede aplicar a varios tipos de PCB, incluidos los PCB rígidos, los tableros blandos y los tableros flexibles de alta densidad.

Hay dos métodos comunes para Flying Lead en paneles flexibles (FPC), a saber, TAB y COF.

TAB (unión automatizada de cinta) es un método que utiliza un sustrato de plástico para transferir el circuito conductor a otro sustrato y conecta el circuito conductor a los pines del chip a través de un recubrimiento de oro. Este método requiere más tiempo.

El método COF (Chip on Film) implica la conexión directa de chips al FPC, lo que requiere cables voladores más cortos y permite la implementación en espacios más pequeños. Este método requiere mayores requisitos técnicos y costos, pero puede lograr una mayor conductividad y confiabilidad.

Ambos métodos de fabricación tienen sus ventajas y desventajas, por lo que es fundamental elegir el método adecuado en función de los requisitos del cliente y las necesidades del proyecto.

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