PCB via plugging Technology

Most of PCB manufacturers use Al sheet to plug vias.We use blank net to make solder mask and plug vias after many experiences, it’s stability and reliability.

As the development of electronics industry, customers put high requirements for PCB surface mounted technology.Via plugging come into being as it connected all circuits,then it must meet below requirement :

(1.) Vias can plugged or not plugged,just ensure it plated in vias wall.

(2.) It must have tin/Pn in vias with thickness 4um, no solder mask inflow into vias lead to tin bead plugging.

(3.) Use solder mask ink to plug vias,no light through vias,no tin ring,no tin bead and surface must be flattening.

There are many of high density and BGA boards required via plugging as the electronics products became smaller,lighter,thinner. 4 factors why customer required via plugging.

Avoid circuits short as tin bead runing around when PCB solder wave process,especially vias in BGA Pad.

Avoid solder flux remain in vias.
Avoid surface solder paste inflow into hole lead to cold solder.
Avoid solder beading run out when solder wave, lead to short circuit.

For surface mounted technology,especially BGA and IC package required surface must be flattening,concavo-convex tolerance +/-1mil,no solder beading.For meet customer requirement, there have many methods to plug vias,the technology time is complex and the hard to control.always happened solder mask peeling after solder wave.

Plugging vias after HASL

The process is: solder mask printing—> HASL—>Pluging—>Solidified . Use non-plugging process to make, use Aluminum sheet or silkscreen to fill the vias after solder wave. the solder mask oil can be liquefied or UV oil just keep the color is in uniformity. this technology can guarantee solder mask no peeling after solder wave.but it will pollute the surface of board. it will lead to cold solder when SMT. many customer don’t accept this method.

Plugging vias before HASL

Use aluminum sheet plugging,solidified,curing and image transfer

This process use NC drill for aluminum sheet and make it to silkscreen and plugging,ensure plugging via plump,solder mask oil can be liquefied or UV oil, the advantage is strong hardness, small resin shrink,good sticky with via wall. the process is : Pre-treatment—>plugging—>curing—>image transfer—> etching—> solder mask printing.

Use this method can guarantee vias be plugged with flattening and no erupt oil,edge of holes oil peeling,but this technology required one time plating copper, make hole wall thickness achieve standard of customer. it must be well plating of whole panel,and must have high capability of curing equipment,guarantee complex remove the remain resin on copper and no smear.

Solder mask printing after aluminum sheet plugging

This technology use NC drilling to make aluminum sheet and make it to silkscreen. use 36T silkscreen make solder mask after plugging,the time is less 30 minutes, the process is : Pre-treatment—> Plugging—>Silkscreen—> Pre-bake—>Exposure—>Development—>Solidified.

Use this method can guarantee via plugged flattening and well covered and solder mask color uniformity. it can ensure no inflow tin to hole and no solder beading after solder wave.

Aluminum sheet plugging,development,pre-solidified.curing,solder mask printing

NC drilling for aluminum sheet and make it to silkscreen and plugging.plugging must be plump and solidified. the process is : Pre-treatmemt—>plugging—>Pre-baking—>development—>Pre-solidified—>solder mask printing.

As this method can ensure no oil peeling and blast oil, but it will risk tin beading in hole.so many customers don’t accept it.

Solder mask printing and plugging at the same time

This method use 36T(43T) silkscreen, install at silkscreen machine and use mat board, make solder mask and via plugging as the same time, the process is : Pre-treatment—>Silkscreen—>Pre-baking—>Exposure—>Development—>Solidified.

This technology use less time and high efficiency,and can guarantee no oil peeling after solder wave and no tin on hole, but as use silkscreen to plugging, there will have much more air,when solidified,air expand,rush and break solder mask film, lead to void,and no flattening.

Posted on 23 Nov 2016
By info@kingsunpcb.com
In PCB knowledge, Technology

PCB material(CCL)’s price continual rising

In recent months,PCB material cost is continual increase lead to China PCB enterprisers are in difficult situation. Especially price soared of copper foil,copper ball,glass fibre,epoxy resin have exceeded the limit of maximum cost of printed circuit enterprises. In pass 10 years, PCB enterprises have cut the price to bottom for scramble market without profit.Now they had to rise PCB price as raw materials pressure.

China epoxy resin industry association market expert said most of China PCB price has been in low position since international IT industry bubble burst during 2001 to 2002 and the economic downturn.even many enterprises running under loss profit.Also because most of PCB enterprise scattered and small compared with OEM,EMS and other terminal customers,lead to PCB enterprises are in low bargain power.meanwhile in recent years, the rising cost of all aspects,raw materials,water and electricity,wages and other rising and downstream customers continue press PCB manufacture in price,PCB enterprises are very difficult in developing.the long-term development of the industry is a challenge.Therefore, reasonable PCB price can keep enterprise vitality.If pcb enterprise lose their vitality due to the lack of profit,it will impact whole electronic industry and hinder the progress of whole electronics industry. in this case, it’s necessary to adjust the price of PCB.

Market experts believe that current adjustment of PCB price is very timely,the whole industry enterprises are very welcome and support this work. according to China epoxy resin industry association market experts,the PCB price adjustment is prerequiste that PCB raw and auxiliary materials continued 2 years of rising and soar in recent,PCB enterprise can not afford such high cost pressure and be forced to adjust price to downstream user.

Raw material prices are determined by supply and demand. it according market rule and can be understood. PCB developed too fast in past years as one of whole industry chain.upstream raw materials in short supply and prices all the way up.as the PCB capacity disequilibrium lead to vicious competition to provide more opportunities for downstream users,most of the PCB running under no profit and can not resist so much range of raw materials price. from this point of view pcb price adjustment is inevitable,it’s the only way to save themselves,but also in line with market rules.

Most of the leading enterprises in the industry analysis and compared different costs for different products to re-establish the reasonable price of each product and one by one to contact to customer to communication of raise price requirements. For a number of low tech products, the enterprise to take the abandoned policy,re-position market follow company ability. and strengthen coordination with customers and inform customer of the company’s raw material rising pressure,and from the service and product quality to further cooperate with the customer.

They believe that the upstream and downstream enterprises need more communication and consultation, the CCL, PCB, the relationship between the 3 plant analysis, communication, interpretation,

Posted on 13 Nov 2016
By info@kingsunpcb.com
In PCB knowledge, Technology

HDI PCB Technology

HDI PCB is High Density Interconnection PCB, It widely used in small BGA board as its more advantages:

Increased interconnection density by miniaturization of holes,pads and conductors.
Provides the possibility to have a via hole connect direct in the SMD or BGA pad.
Improved signal integrity due to reduced tracklength.
Improved possibility to maximization of ground connections.
Opportunities of better thermal enhancement.
Improved reliability by stepping up technology rather than compromising existing design rules.

Type of HDI Blind via:

Micro via hole: 1+N+1, vias no need plating filling
Solid via hole: 1+N+1, vias need plating filling
Stagger via hole: 1+1+N+1+1, dislocation laser drilling
Stack via hole: 1+1+N+1+1, coordinate laser drilling
Skip via hole: Laser D13, isolation from L2.
Step via hole: 1+1+N+1+1,coordinate laser

Type of drilling mode:

1. Large Conformal mask: Conformal mask, ladder-shaped laser drilling

2. Conformal Mask:Conformal mask, rectangle-shaped laser drilling

3.Direct Laser Drill: No need conformal mask, rectangle-shaped laser drilling

Definition of HDI type:

1+N+1: N is standard layer,1 is one time laser.

Process: Drilling after lamination—>Add a copper to laminate—>Laser drilling

E.g. : 1+4+1

1+1+N+1+1: N is standard layer, 1+1 is twice laser.Process: Drilling after lamination—>Add a copper to laminate—>Laser drilling—>Add a copper to laminate—>Laser drilling

1+1+1+N+1+1+1: N is standard layer,1+1+1 is three times laser

Process: Drilling after lamination—>Add a copper to laminate—>Laser drilling—>Add a copper to laminate– ->Laser drilling—>Add a copper to laminate—>Laser drilling

Any Layer:

Use one by one layer to laser drilling

HDI PCB design Rule

1+N+1

2+N+2 Stagger Via

2+N+2 Stack Via

Material of HDI:

The material of HDI board contain RCC,LDPE,FR4

RCC: Resin coated copper,it’sconstituted by coarse surface, heat-resisting, anti-oxidation copper and resin.it used in thickness>4mil. Resin of RCC has same performance of FR4 Prepreg. RCC is new material with no-glass fibre.It facilitate laser via ethching, retain multilayer board light and thin. Additional RCC has 12pm,18pm copper, it’s easy to fabricate.

LEDPE
FR4: It used in thickness<=4mil. always use PP 1080. HOZ, 1/3OZ is thepriority choice for HDI board.

Posted on 21 Oct 2016
By info@kingsunpcb.com
In PCB knowledge, Technology

What is the min trace width and space of heavy copper PCB?

New PCB designer always confuse how to build the min trace width and space for heavy copper PCB. Now PCB manufacturer engineer tell you how to do?

The min. trace width/space at inner layer :

The min. trace width/space at outer layer:

More PCB knowledge, please visit www.kingsunpcb.com

Posted on 18 Sep 2016
By info@kingsunpcb.com
In PCB knowledge, Technology

How to improve the voids of PCB resin plugging?

PCB resin plug via always has voids problems, it lead to solder area reduce and bring soldering reliability problems.The article analyses the generation factors of voids and how to improve it?

Via in pad technology is used in high frequency design to reduce inductance and increase density, means via plug is the necessary process. The design require the surface nearly flat,as it may cause soldering and reliability problems. Nowdays the process generally plug resin into core board and metallization.Via is filled with resin of printing,curing after using special ceramics and remove excess resin and then slip to pattern plating. Lead to main defects: plugging resin sag,voids,cracks. We can solve plugging resin sag with plug plumpness. Crack caused by its components and general resin solidifying parameters. Voids seriously affect the reliability of production parameters when it happened surface of pad . Voids is also difficult to improve although adjusted the general parameters.Therefore,this paper focuses on analyses and test the factors of voids.find out control method of plug voids.

Plug voids is actually air bubbles in resin, not be overflowed when solidifying. Although Plugged process is normal,but Plug parameters, Screen mesh,Solidifying method,Panel placement method,Plug method,Resin type affect the quality of plugged via.

We will follow the factors to do experiment.

Experiment material：

Manufacture design:

9 units per panel, 0.1mm and 0.2mm via in each units,400 drilling in each via.

Experiment process:

Sheet Cutting—>Brown Oxide —>Lamination—>laser drilling—>NC drilling—>Electroless copper(1)—>PTH(1)—> resin plug—>Solidify—>Ceramic Grinding—>Electroless copper(2)—>Pattern Plating(2)

Confirmation Method:

Use microscope observe section after Ceramic Curing or Pattern Plating

The result of experiment:

1. Different screen mesh and plug parameter

Summary: Screen mesh,plug parameter on the effect of voids is smaller, all has a large number of voids in different place.

2. The result of Solidifying method and Panel placement method

Summary: Solidifying method is no effect for voids,Panel placement method has a certain effect on the voids,but the effect is not obvious.

3. Plug method

Summary: use recycle resin,all the three plug methods have voids. Different result from different plug methods,the quality of plugging: Vacuum plug<Aluminum board plug<Screen printing plug.

4. Plug method and resin type

Summary: use Vacuum plug method, there is no voids for new resin and recycle resin with vacuum removed bubble.

Summary of experiment:

1.Plug parameter,Screen mesh,Solidifying,Panel placement method are very small effective for plug.

2.Use vacuum removed air bubble is great improve for plug voids.

3.Different plug methods lead to different quality of plug.Vacuum plug is the best quality for resin plugging.

4.Use Vacuum plug+new resin or recycle with removed bubble will don’t produce voids.

Posted on 2 Sep 2016
By info@kingsunpcb.com
In PCB knowledge, Technology

How to calculate impedance value before PCB fabrication

It’s very important how to calculate impedance value before PCB fabrication.

What is impedance?

Impedance is the total resistance of alternating current produced at known frequency.it’s resistance sum of signal layer and reference plane.

Impedance Type

Characteristic impedance

Characteristic impedance is the ratio of voltage and current of a single wave propagating along the line.Signal produces reflection in the impedance discontinuity if characteristic impedance of transmission path changes when signal is in the transmission process.

Differential impedance

Trace carries the opposite polarity of two same signal waveform transmission by individual,subtraction the two differential signal at receiver. Differential impedance is the impedance between the two lines.

Even mode impedance

Even mode impedance is the impedance of one line when the pair is driven commonly.

The factors affect impedance

W—Trace width/space. The impedance decrease when trace width increase, The impedance increases when the trace space.

H1—Insulation thickness. The impedance increase when insulation thickness increase

T—Copper thickness.The impedance decrease when copper thickness increase

C1—Solder mask thickness.The impedance decrease when solder mask thickness increase

Er—Dielectric constant. The impedance decrease when dielectric constant increase

Undercut—W1-W2. The impedance increase when undercut increase.

Impedance calculate equation

Zo=[87/( Er +1.41)^1/2]*ln[5.98H/(0.8W+T)]

For example: Calculate impedance 50 ohm for 4 layer board :

L1（TOPLAYER） 1.9mil

1080+2116 7.3mil

L2（GND） 1.2mil

Core 44.5mil

L3（VCC） 1.2mil

1080+2116 7.3mil

L4（BOTTOMLAYER） 1.9mil

Board thickness：65*0.0254＝1.6mm

Er=4.2 H=7.3mil T=1.9mil

Ln =2.71828

Input equation：50=[87/( 4.2 +1.41)^1/2]*ln[5.98×7.3/(0.8W+1.9)]

Result：W=11.6

Posted on 9 Aug 2016
By info@kingsunpcb.com
In Technology

The most popular PCB surface treatment

PCB surface treatment ensure circuit board had good solderability or electrical property.Due to the nature of the copper oxide form tend to be in the air, it’s impossible to maintain the original copper,so copper requiring additional processing. Below is the most popular PCB surface treatment.

HASL and HASL-LF

HASL is hot air solder leveling. It coated with molten tin(Pb) solder and heating the entire compressed air(blowing) level technology to form a layer of anti-oxidation of copper,but also provide good solderability coating.The HASL usually sinking in molten solder,air knife blow the solder liquid level before solidification.air knife can make solder copper to crescent-shaped with minimized and to prevent solder bridging. HASL-LF is HASL lead free.

OSP

OSP(Organic Solderability Preservatives) is a process of PCB surface-treated copper foil ROHS compliance requirements.It is grown an organic film layer with chemical methods in the clean bare copper surface.This membrane has oxidation resistance,thermal resistance and moisture resistance to protect the copper surface does not rust in the normal environment.It be required rapid clearance to flux in the subsequent high temperature solder.So the clean exposed copper surface can be combined with the molten solder joints immediately became solid in a very short period of time.

IMMERSION GOLD

Immersion gold surface is wrapped with heavy nickel electrical gold alloy,which can be long-term protection PCB. In addition it has great patience for the environment that other surface treatment processes do not have . Immersion Gold can also prevent dissolution of copper,which will benefit the lead-free assembly.

IMMERSION TIN

Since all current solders are tin-based, the tin layer can be matched with any type of solder materials. Immersion Tin process can formed planar copper-tin intermetallic compound, this feature makes immersion tin having a good solderability like HASL but without flatness problem. Immersion Tin board can not be stored for too long,Assembly must be followed the time of Immersion Tin.

IMMERSION SILVER

Immersion Silver is between organic coating and Immersion Gold, the process is relatively simple and fast.the silver is till able to maintain good solderability even exposed to heat, humidity and pollution environment.Immersion Silver does not have good physical strength possessed like Immersion gold because there no nickel under silver layer.

ENEPIG

ENEPIG(Electroless nickel electroless palladium Immersion Gold) is more palladium layer compared with Immersion Gold. Palladium appears to prevent corrosion caused by substitution reaction. It well prepared for Immersion Gold.Gold is closely covering the palladium,provide a good connection surface.

Hard gold plating

In order to improve the wear resistance of products,increase the number of plug of gold finger, hard gold plating surface is necessary.

Posted on 15 Jul 2016
By info@kingsunpcb.com
In PCB knowledge, Technology

How to choose PCB material?

Some comments for select PCB materials:

For electronic products, using FR4 epoxy fiberglass materials.
For high temperature application or flexible circuit board, using polyimide materials.
For high-frequency circuit, using Rogers or Teflon materials.
For high heat dissipation products, using metal core materials,like Al based material.

Five factors we should consider when select PCB material:

High transition temperature(Tg) degree materials is necessary for high speed digit PCB.
Low coefficient of thermal expansion(CTE) is necessary.Since the X.Y and coefficient of thermal expansion in the thickness direction is inconsistent,it’s easy lead to PCB deformation,and cause PTH hole break and components damage.
Requires a high heat resistance.General requirements for PCB to have 250℃/50s heat resistance.
Requires material flattening. SMT soldering require PCB warpage <0.0075mm/mm.
High-frequency circuits require high dielectric constant,low dielectric loss materials. Insulation resistance, breakdown voltage, arc resistance should meet product requirements.

FR4 property according to IPC-4101

Posted on 28 Jun 2016
By info@kingsunpcb.com
In PCB knowledge, Technology