CN109688700A

CN109688700A - A kind of welding resistance windowing design of PCB pad

Info

Publication number: CN109688700A
Application number: CN201811611958.9A
Authority: CN
Inventors: 羊宋英
Original assignee: Shenzhen Pengying Trading Co Ltd
Current assignee: Shenzhen Pengying Trading Co Ltd
Priority date: 2018-12-27
Filing date: 2018-12-27
Publication date: 2019-04-26

Abstract

The invention discloses a kind of windowings of the welding resistance of PCB pad to design, welding or detection is needed to use on pcb board and pcb board including the matrix as carrying pad, the pad is corresponding welding resistance windowing, the minimum widith of the pad is greater than 0.2mm, the welding resistance of the pad opens a window reduction amount smaller than pad and unilateral not less than contraposition deviation value, and the resist thickness is less than 20um.This programme solves the trailing phenomenon of conventional welding resistance windowing, effectively prevents gravestone effect, improves the quality of pcb board, reduce scrapping for wiring board, reduces the production cost of enterprise；Pad is easy to warp or fall off, cause quality problem on pcb board in the case where stress, in the environment of high temperature or humidity；Welding resistance windowing is than weldering shallow bid welding resistance design, due to peripheral sealing simultaneously because the adhesiveness of solder mask, makes pad be able to bear more power, is not easy to warp under high temperature or the environment of humidity, improves quality.

Description

A kind of welding resistance windowing design of PCB pad

Technical field

The present invention relates to the productions of PCB to design and produce field, and the welding resistance of especially a kind of PCB pad, which opens a window, to be designed.

Background technique

With reaching its maturity for wiring board technology, and the competition of wiring board manufacturing enterprise is more and more fierce, so that wiring board Productive profit it is lower and lower.Therefore wiring board manufacturing enterprise constantly improves to its production technology and perfect, reduction line Road plate rework rate in process of production and bad product rate save production investment, reduce production cost.

At present for the pad design of wiring board, traditional production method be direct-on-line road plate pad on directly adopt Welding resistance windowing design, pad is exposed.It is isolated there are on pcb board that pad, which has part, pad some and route Connection be attached on pcb board, there are also part pad be link together with copper sheet either copper sheet a part.It is set in conventional In meter, welding resistance windowing is an equal amount of design, and the junction of pad and connection is caused to leak copper, while the weldering on the copper sheet Bonding area becomes larger after the windowing of disk welding resistance, and the pad of same class device is not of uniform size on pcb board, makes to become in welding process Abnormal trouble, and then cause device attachment abnormal, cause quality hidden danger.The design of pad and connection, welding resistance windowing system After work, the pad made has certain trailing phenomenon, i.e., " the gravestone effect " usually said.It makes in this way Wiring board will appear following problem: first is that seriously affecting appearance, influence the quality of product；Second is that hangover is serious, very It is easy to cause short circuit in note part, three, tin cream displacement causes device deviation, while rosin joint easy to form during patch, four, right Welding contact surface is uneven during the attachment of multi-pipe pin device, leads to failure welding, plate is caused not to be available, increase bad The generation of product rate, increases production investment and cost, and waste of resource aggravates enterprise's production burden, while influencing the prestige of company.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of windowings of the welding resistance of PCB pad to design, and makes patch welding process In be not easy deviation, bonding area is uniform, while will not generate trailing phenomenon.

In order to solve the above technical problems, the present invention adopts the following technical solutions: the welding resistance of the PCB pad, which opens a window, to be designed, packet It includes to need on the pcb board and pcb board of the matrix as carrying to weld or detect and use, the pad is corresponding to have welding resistance to open Window, the minimum widith of the pad are greater than 0.2mm, and the reduction amount that the welding resistance windowing of the pad is smaller than pad and unilateral is not less than Contraposition deviation value, the resist thickness are less than 20um.

Design concept according to the present invention, pad corresponding position of the present invention are less than for the thickness of entity structure and pad 70um。

The center of design concept according to the present invention, pad of the present invention is identical as the center that welding resistance opens a window and welds The size of disk is 0.1mm or more bigger than the size of welding resistance windowed regions.

Design concept according to the present invention, pad of the present invention are IC pad or/and BGA pad.

Compared with prior art, the present invention have it is following the utility model has the advantages that

(1) it solves the trailing phenomenon of conventional welding resistance windowing, effectively prevents gravestone effect, improve the quality of pcb board, reduce line Road plate is scrapped, and the production cost of enterprise is reduced.

(2) pad is on pcb board, is easy to warp or take off in the case where stress, in the environment of high temperature or humidity It falls, causes quality problem；Welding resistance windowing is than weldering shallow bid welding resistance design, due to peripheral sealing simultaneously because the adherency of solder mask Property, so that pad is able to bear more power, be not easy to warp under high temperature or the environment of humidity, improves quality.

(3) the welding resistance windowing of similar pad is in the same size, solves the problems, such as that pad is different by tin size, makes structure It is more beautiful.

(4) consistent by tin area, reduce and mount offset caused by stream tin, while reducing welding caused by due to offset Bad and rosin joint.

Detailed description of the invention

Fig. 1 is the composing structure figure of big plate pcb board；

Fig. 2 is BGA pad fenestration schematic diagram；

Fig. 3 is IC pad fenestration schematic diagram.

Specific embodiment

For the technical solution that the present invention is furture elucidated, below with reference to attached drawing, the present invention is described further.

A kind of 4 design of welding resistance windowing of PCB pad of the invention, the matrix pcb board including carrying pad, pcb board can be with It is single sided board, dual platen or multi-layer board, the outer-layer circuit of pcb board is connected with pad 3, and the pad 3 is various sets Meter, such as: round, rectangular, rectangle either anisotropic approach meets different attachment or welding demand；The pad 3 is set It counts position according to demand, can be divided into three classes, for one kind to be individually isolated there are on PCB, one kind is that connection is attached to pcb board On, another kind of is that design connects on copper sheet or with copper sheet, and 3 size of pad corresponding to the device of similar size is identical sets Meter.

For 3 minimum widith of pad less than 0.2mm, according to 4 production of normal design welding resistance windowing, in production, to covering In copper foil etching process on copper sheet, there is certain etching factor, certain tolerance can be generated, in the contraposition printing and exposure of welding resistance Light equally has certain deviation in rinsing, and etching and the deviation aligned are routinely the range of 0.05-0.07mm, after leading to printing Appearance opens a window not completely on pad 3 or welding resistance opens a window, and 4 unilateral areas are too small to cause solder mask to be easy to fall off, and easily causes Quality problem, while in paste solder printing and welding process, it is easy, device displacement formation patch during mobile to low-lying side It causes to weld scarce tin or welding rosin joint.

3 size minimum widith of pad is greater than 0.2mm, according to the size of pad 3 and design requirement production welding resistance windowing 4, institute The open a window size in 4 regions of welding resistance is stated to compare the unilateral small 0.1mm or more of size of pad 3, the i.e. width of same position welding resistance windowing 4 Degree is 0.1mm or more smaller than the width of pad 3, carries out welding resistance printing according to the design of welding resistance windowing 4, exposure, development, rinses production Pad 3 opens a window out, and the windowing of similar device is in the same size and is not in trailing phenomenon, and windowing is in the same size to optimize appearance knot Structure, meanwhile, the in the same size of welding resistance windowing 4 makes pad 3 leak copper face product unanimously, and the amount of print solder paste is uniformly arranged, welding process Middle 3 surfacing fast and easy Mount Device of pad, while also having prevented to move because mounting caused by the unevenness of paste solder printing amount Position, and then quality is improved, reduce cost.

In order to facilitate production, preferably the thickness of welding resistance is not more than 20um, while the thickness of pad 3 is less than 70um；Its cause It is to be easy to cause 3 area depression of pad when resist thickness is greater than 20um, needs a certain amount of tin cream filling recessed in welding process Area is fallen into, when the thickness of tin cream arrives certain thickness, since tin cream is circular crystal grain composition, is easy to roll shifting during attachment Position, causes quality abnormal, while being also easy because lacking tin causes rosin joint.When being greater than 70um for 3 thickness of pad, PCB needs are held The electric current and voltage received are bigger, and the thickness of solder mask needs to reach certain insulation thickness, in order to ensure safety and production Rapidly and efficiently, therefore it is not recommended that the welding resistance windowing 4 using this PCB pad 3 designs.

With reference to Fig. 1, in order to convenient for production, in the time of production, contraposition is equipped in the big plate edges of boards of the PCB and plate Pad 1, the contraposition pad 1 are equipped with detection windowing accordingly 2, welding resistance 4 structures of windowing needed in the detection windowing 2 and plate It is identical, and at the same time designing the contraposition pad 1 and detection windowing 2 in contraposition deviation allowed band according to the production process.It is etching Out after contraposition pad 1, carry out welding resistance printing, welding resistance exposure after according to detection windowing 2 on pad 3 the case where carry out confirmation contraposition be No qualification, detection 3 periphery of pad have substrate exposed then to be unqualified, and detection windowing 2 is then qualification completely on pad 3.

Fig. 2 is 3 fenestration schematic diagram of BGA pad, and in BGA area, the spacing of BGA pad 3 and relative position all have It is required that, the position of opposite welding resistance windowing 4 equally requires, 3 spacing of BGA pad it is smaller when, not can guarantee BGA pad 3 Between welding resistance bridge, when patch, tin cream flowing causes short circuit；If reducing the size of BGA pad 3, retain 3 welding resistance bridges of BGA pad, The contact area that will appear pad 3 and substrate is too small, is easy to fall off；With reference to the design of Fig. 2, welding resistance ensure that between BGA pad 3 Bridge, simultaneously for the design for being equipped with route between BGA pad 3, can etch come under the premise of more convenient printing welding resistance, It places conducting wire side leakage and causes short circuit, the welding resistance windowing 4 on BGA pad 3 is smaller than pad 3, and the adhesive force of solder mask increases BGA The adhesive strength of pad 3 favorably has the promotion of production efficiency and the guarantee of product quality.

It, equally can be with the welding resistance windowing 4 of IC pad 3 is smaller than pad 3, contraposition for the design of IC pad 3 with reference to Fig. 3 Deviation not will lead to the reduction of welding surface machine, while compared to normal windowing, welding region forms depressed area, reduces tin cream welding When flowing, normal welding resistance windowing 4 is bigger than pad 3, aligns situation about occurring on deviation especially copper sheet and causes 3 size of pad Different, tin is in uneven thickness in welding process, when forming welding offset, while welding, due to the thickness between pad 3 and substrate Drop is spent, tin cream tin cream in attachment welding is easy to flow to substrate area, forms attachment welding displacement or scarce tin；It is easy simultaneously Cause stream tin welding short circuit.

Claims

The design 1. a kind of welding resistance of PCB pad opens a window, including needing to weld on the pcb board and pcb board as the matrix for carrying pad It connects or detects and use, the pad is corresponding welding resistance windowing, which is characterized in that the minimum widith of the pad is greater than 0.2mm, the welding resistance of the pad open a window reduction amount smaller than pad and unilateral not less than contraposition deviation value, and the resist thickness is small In 20um.
The design 2. welding resistance of PCB pad as described in claim 1 opens a window, which is characterized in that the pad corresponding position is real The thickness of body structure and pad is less than 70um.
The design 3. welding resistance of PCB pad as claimed in claim 1 or 2 opens a window, which is characterized in that the center of the pad and resistance Weld windowing center is identical and the size of pad is 0.1mm or more bigger than the size of welding resistance windowed regions.
The design 4. welding resistance of PCB pad as claimed in claim 3 opens a window, which is characterized in that the pad be IC pad or/ With BGA pad.