Shengyi S1141 (TG 130) is a good alternative to lower the cost of your project, at the sacrifice of some quality. In cases where higher quality is needed, we recommend Shengyi S1000-2M (TG 170), which is the closest in quality to Isola FR406 (Tg 170). Where quality is the highest priority, we would recommend utilizing ITEQ IT180A (TG 180), which is also RoHS compliant. ITEQ IT180A (TG 180) is comparable in quality and to Isola 370HR (TG 180). We at Hopetimepcb would suggest using Shengyi S1000H (Tg 130) for typical projects. We would recommend using one of the higher quality laminate materials if any of these three conditions occur:
1) If the PCB Design has 8 or more layers
2) If Copper Board is heavy with a copper weight heavier than 3oz
3) If PCB Board is thin with a board thickness of less than 0.5mm

1.4  Copper Weight & Heavy Copper for Materials
Copper clad FR-4 laminate materials are measured using ounce (oz.) weight per square foot.
• 0.25 oz. = 0.00035” (8.75μm)
• 0.5 oz. = 0.0007” (17.5 μm)
• 0.75 oz. =0.00105” (26.25μm)
• 1.0 oz. = 0.0014” (35 μm)
• 2.0 oz. = 0.0028” (70 μm)
• 3.0 oz. = 0.0042” (105 μm)
• 4.0 oz. or more = 0.0056” (140 μm) or more
Heavier copper weights allow for higher current carrying capability and heat dissipation characteristics in high power designs, making heavy copper a common choice for automotive, power distribution, and welding equipment industries . Hopetimepcb Electronics is capable of fabricating multi -layer PCB boards with a maximum copper weight of 10 oz. Copper weight of 4 oz. or higher will require an additional estimate, and may also affect lead times. The specified copper weight for a board will also impact the trace width and spacing requirements of the board, as shown in Table 5, below:
1.5 RF Substrates
For radiofrequency applications requiring very high fidelity, some clients find that standard FR4-type material does not meet signal loss requirements due to its relatively high dielectric constant of approximately 4.5. As such, specialized dielectric materials for RF applications offer lower dielectric constant to satisfy such design requirements . Hopetimepcb stocks Rogers RO4350 B as our standard RF substrate . We offer core thicknesses of 10mil, 20mil or 30mil in stock, and the copper weight can be 0.5oz/0.5oz or 1oz/1oz. Other sizes available for special order with added lead -time are 6.6mil, 13.3mil, 16.6mil, 60mil. The dielectric constant of this material is 3.76 at 1GHz and averages 3.66 for 8GHz to 40GHz. Further details can be found on the material’s datasheet. Additional RF materials may be available upon special request with added lead time.
The dielectric constant of a material describes the ratio of that material’s permittivity to the permittivity of vacuum. Technically speaking, a material’s permittivity describes the electric field strength between two chargesseparated by that material. The dielectric constant of a material affectsits parasitic capacitance, which can become quite significant at high operational frequencies. Equation 1 and Equation 2 illustrate the effects of dielectric constant on signal loss. Equation 1 describesthe capacitance of a parallel-plate capacitor—derived from Maxwell’s Laws—where any two copper layers of a PCB can be viewed as parallel plates separated by the dielectric material. The k variable represents the dielectric constant in Equation 1, and clearly, the capacitance increases with k. Equation 2 described capacitive reactance, which decreases inversely to capacitance and frequency; this explainsthe increased significance of material dielectric constant for high-frequency operation.

      

While standard rigid FR4-type materials are composed of glass-reinforced epoxy, RF materials primarily make use of Polytetrafluoroethylene, also known as PTFE, or by its trademark name: Teflon. In addition to its advantages in dielectric constant, PTFE materials also boast impressive thermal characteristics for hightemperature PCB applications. With high TG (glass-transition temperature) values, reaching up to 280°C, PTFE materials are suitable for both high frequency and high-power applications.
When preparing your project for PCB Fabrication using PTFE materials, it is important to reach out early in the process, if possible, for a quotation. Projects involving Rogers and other high-frequency PCB materials will require a special estimate, not covered by Hopetimepcb’s online quoting tool. Extra care is necessary in PCB Fabrication for high-frequency materials since PTFE is relatively soft compared to FR4-type materials,making it more susceptible to damage while handling . The fabrication of plated through -holes and slots is also more difficult for PTFE materials, due to the famous non-stick properties of Teflon.

1.6 Metal-Core PCBs
For PCBs with very high thermal demands , Hopetimepcb can also provide professional metal -core PCB fabrication options, where a metal base is bonded to the copper signal layers, separated by a dielectric for insulation. Metal-Core PCBs are often used to help conduct heat away from vital components in high power designs, such as amplifiers, power supply modules, motor drives, commercial lighting, and many automotive applications. The standard Metal-Core PCB design consists of three main components:
Signal Layer: Contains copper pads and traces, subject to copper weight specifications defined in Section 3.4
Dielectric Layer: Offers high electrical insulation and high thermal conductivity
Metal Core: Most commonly aluminum for low-cost, but other options such as copper are available
Figure 2 shows a simple diagram of the standard Metal-Core PCB components described above:

 
Hopetimepcb generally provides metal-core PCB fabrication with core thicknesses ranging from 0.031” to 0.125”, but we can also handle orders for other sizes with a special estimate. We also provide heavy copper options for the signal, power, and ground layers of your design, from 0.5 oz. to 10 oz. or more.

1.7 Multi-Layer Stack-Up
Multi-layer boards have some physical properties which need to be considered by both the designer and manufacturer in order to ensure quality construction. Multilayer board designs should have an even number of layers for the best quality. Choose each layer’s dielectric thickness from the provided core or prepreg thicknesses listed in Table 3 and Table 4. For possible combinations , please consult our Hopetimepcb manufacturing team for what are suitable and achievable dimensions and tolerances.

It is recommended that multi-layer designs balance the lay-up relative to the Z-axis median to minimize bow and twist. In other words, a layer stackup list should read the same from top to bottom as it does from bottom to top. Dielectric thickness, copper thickness and the location of layers, median, Z-axis need to be balanced. If the Multi-layer design rules are adhered to, the PCB should meet specifications for the maximum allowable bow and twist of 0.25mm per 25mm (1%) or better. It is also beneficial to balance the circuitry distribution between the front and back of the board as much as possible. This is more of a concern with thicker copper weights. 

Thickness Tolerance increases as the overall thickness of a multi-layer board increases. You should specify a tolerance of ±10% for the overall thickness, which is thicker than 1mm, or +/-0.1mm for 1mm thickness or thinner. Also, you need to always indicate where the thickness measurement is to be taken.

1.8 Multi-Layer Stack-Up Recommendation
We at Hopetimepcb can fabricate multi-layer PCB boards up to a maximum of 40 layers. PCB’s with more than 20 layers will require an additional estimate before production can begin. Below are our recommended stackups for a normal board thickness of 62mil. We at Hopetimepcb do offer custom stackups, please let us know what you need, and our CAM engineer will review it for feasibility 

1.9 Buried Capacitance
Buried Capacitance is a PCB production methodology where decoupled capacitance is gained from inserting a very thin dielectric layer inside a PCB. Adding buried capacitance to a board eliminates the need for decoupling capacitors, freeing up more PCB space as redundant pads and conductors can be removed. Having a lower number of components on a PCB will lower the cost and simplifies PCB assembly operations and also reduces the number of required steps. New technology, like this, grants greater freedom to designers, which allows them to design PCBs with greater performance, or equivalent performance in a smaller board size. Lastly, using buried capacitance can also reduce noise and high-frequency electro-magnetic interference to improve PCB quality. Figure 3 (below) illustrates an 8 layer board with buried capacitance.

1.10 Material Substitutes (North America vs China)
China Substitute Materials

 

 

• Shengyi S1141 (TG 140)

• Td 300, Dk 4.2, Df 0.015

• Material Datasheet Link

• Shengyi S1000H (Tg 150)

• Td 325, Dk 4.38, Df 0.015

• Material Datasheet Link

• Shengyi S1000-2M (TG 170)

• Td 340, Dk 4.28, Df 0.017

• Material Datasheet Link

• ITEQ IT180A (TG 180)

• Td 350, Dk 4.3, Df 0.015

• Material Datasheet Link

North American Laminates

• Isola FR406 (TG 170)

• Td 300, Dk 3.93, Df 0.0167

• Material Datasheet Link

• Isola 370HR (TG 180) 

• Td 340, Dk 4.04, Df 0.021

 

• Material Datasheet Link

Finally, apart from the laminate quality, we must also take the available laminate’s material cost and delivery lead time into account. Since Hopetimepcb’s PCB Fabrication and Assembly facilities are based in China,the cost for importing North American laminates would be higher and increase the lead time, as illustrated in the chart above. Thus, from this comparison chart, we can conclude that the use of local substitute is preferable due to the lower material costs and shorter lead time.

  

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